Friction Stir Spot Welding of AA6082-T6: influence of the most relevant process parameters and comparison with classic mechanical fastening techniques

The results of an experimental study on friction stir spot welding (FSSW) of AA6082-T6 are reported. In particular, process mechanics is highlighted and joint strength is considered in relation to varying the most relevant process parameters. Furthermore, the results obtained are compared with those derived from the application of traditional mechanical fastening techniques such as clinching and riveting. In this way the effectiveness of FSSW is highlighted.

Formability of Friction Stir Welded AZ31 Magnesium Alloy Sheets

The formability of friction stir welded AZ31 magnesium alloy sheets was investigated by means of uniaxial tensile and hemispherical punch tests performed under different process conditions. The results of the tensile tests were analysed in terms of flow stress and ductility at different temperature and strain rate; the hemispherical punch tests, carried out at different temperatures, provided the limiting dome height. The formability of FSW-ed blanks was compared to the one exhibited by the base material in order to evaluate the quality of the welded joints.

Influence of the distance between rivets in self-piercing riveting bonded joints made of carbon fiber panels and AA2024 blanks

Abstract The increasing use of new materials alternative to steel in manufacturing industry has led to a greater emphasis on the improvement and the development of specific joining approaches allowing to get effective mechanical properties even when different materials are joined together. It should be observed that often the traditional welding techniques show several limitations as aluminum or magnesium alloys are used, and, what is more, they are not compatible with composite materials. The development of structures made of these materials has renewed the use of mechanical fastening operations. The present paper investigates the influence of the distance between rivets in self-piercing r…

Failure modelling of friction stir welded joints in tensile tests

Process Mechanics in Friction Stir Welding of Magnesium Alloys: Experimental and Numerical Analysis

Light weight construction is a major task within automotive and aircraft industry due to lower fuel consumption or increase the possible payload. Structural or exterior shell components are more and more manufactured out of aluminum alloys for this reason. A further weight reduction could be achieved by the substitution of aluminum alloys by magnesium alloys. Also the application of blanks with a varying thickness is a possibility to realize light weight design. To combine the advantages of weight reduction by the use of magnesium alloys and tailored welded blanks (TWBs), an effective joining technique is required. Friction Stir Welding can be used for difficult to be welded magnesium alloy…

Influence of material characteristics on plastomechanics of the fsw process for T-joints

Abstract The potential of friction stir welding (FSW) has thoroughly been investigated by several authors, however their focus has primarily been on butt joints. T-joints are of paramount interest for transportation industries especially due to their capacity to straighten panels. Welding of T-joints is very challenging due to thin walls, poor location of the rib–web interface and the requirements for corner-fillets. This paper investigates FSW of T-joints of two popular aluminum alloys, i.e. 2024-T4 and 6082-T6, and the role played by the material characteristics on joining. First, an experimental study is carried out with specially designed fixture to determine the effect of process condi…

A macroscale FEM-based approach for selective laser sintering of thermoplastics

A numerical approach to model the selective laser sintering (SLS) of polypropylene is proposed. A 3D thermal model was developed and thus enables the prediction of the temperature fields and the extension of the sintered area in the powder bed taking into account the phase change during multiple laser passes. Powder–liquid, liquid–solid and solid–liquid phase changes were modelled during the SLS and the subsequent cooling processes. Then, a 3D thermomechanically coupled model was set up based on the temperature results of the thermal model in order to predict the distortion of the produced parts after cooling down. Different pre-heating temperatures were considered, highlighting their…

Comparative analysis of bonding mechanism in solid state metal working processes

The Piwnik and Plata pressure-time bonding criterion was applied to Friction Stir Welding, Linear Friction Welding, Porthole Extrusion and Roll Bonding. A neural network was set up, trained and used to predict the bonding occurrence starting from the main field variable distributions calculated through specific numerical models developed for each process. The analysis of the results permitted to predict the occurrence of solid bonding and to highlight differences and analogies between the processes in order to obtain sound solid welds.

CDRX modelling in friction stir welding of aluminium alloys: a neural network based approach

CDRX modelling in friction stir welding of aluminium alloys

In the paper a numerical model aimed to the determination of the average grain size due to continuous dynamic recrystallization phenomena (CDRX) in friction stir welding processes of AA6082 T6 aluminum alloys is presented. In particular, the utilized model takes into account the local effects of strain, strain rate and temperature; an inverse identification approach, based on a linear regression procedure, is utilized in order to develop the proper material characterization.

Metallurgical Phenomena Modelling in Friction Stir Welding of Aluminium Alloys: Analytical vs. Neural Network Based Approaches

In this paper, the metallurgical phenomena occurring in friction stir welding processes of AA6082-T6 and AA7075-T6 aluminum alloys are investigated. In particular, to predict the local values of the average grain size, either a simple analytical expression depending on a few material constants or a properly trained neural network is linked to the finite element model of the process. The utilized tools, which take as inputs the local values of strain, strain rate, and temperature, were developed starting from experimental data and numerical results.

Damage and fracture study of cold extrusion dies

Abstract In the present paper die fracture in cold extrusion was investigated considering a few different die reduction zone geometries. A former finite element method (FEM) analysis of the process was developed to obtain the contact pressure distribution at the workpiece–die interface for each of the investigated geometries; subsequently a stress and strain analysis utilizing the BEM code Franc3D was carried out, with the aim to evaluate the crack propagation at each loading cycle, i.e. at each extrusion process. In this way the die life for each of the investigated extrusion die geometries was compared utilizing the Paris law and the values assumed by the stress concentration coefficient …

Sample building orientation effect on porosity and mechanical properties in Selective Laser Melting of Ti6Al4V titanium alloy

Abstract In recent decades, the focus of research has shifted towards new production technologies with the aim of optimizing production and reducing costs. These innovative technologies include additive manufacturing processes as Selective Laser Melting (SLM). The analysis of the literature on the identification of optimal building orientation to maximize the mechanical properties and minimize porosity of the final products highlights contrasting results, denoting that the thermomechanical complexity of the process, as associated with the variation of the building orientation, has not been fully clarified. A study in which the building orientation effect was evaluated together with the geom…

Friction stir spot welding of aluminum alloys

Experimental and Numerical Study on Linear Friction Welding of AA2011 Aluminum Alloy

Linear Friction Welding (LFW) is a solid-state joining process used for non-axisymmetric components. LFW involves joining of materials through the relative motion of two components undergoing an axial force. In the process, the heat source is given by the frictional forces work decaying into heat and determining a local softening of the material and eventually the needed bonding conditions. In the paper, an experimental and numerical campaign is proposed for AA2011 aluminum alloys welding. Different case studies are considered with fixed oscillation frequency and varying pressure at the interface between the specimens. Constant oscillation amplitude and specimens geometry is used. The calcu…

Influence of Process Parameters on the Product Integrity in Friction Stir Extrusion of Magnesium Alloys

Friction Stir Extrusion is an innovative direct-recycling technology for metal machining chips. During the process a specifically designed rotating tool is plunged into a cylindrical matrix containing the scraps to be recycled. The stirring action of the tool prompts solid bonding related phenomena allowing the back extrusion of a full dense rod. This process results to be particularly relevant because allows the reuse of the scrap without any previous treatment. Experiments have been carried out in order to investigate the influence of the process parameters on the extrudes quality and a numerical model has been developed in order to simulate the evolution of the material flow.

An exploratory study for analyzing the energy savings obtainable by reshaping processes of sheet metal based components

Abstract Producing materials causes about 25% of all anthropogenic CO2 emissions. Reshaping could be one of the most efficient strategy to foster material reuse and lower the environmental impact due to material production. Sheet metal forming processes can be applied to reshape sheet metal based component. This research field is still almost unexplored and the actual environmental impact saving potential has not been quantified. The present paper aims at starting to cover this research gap, a modeling effort to quantify the environmental impact saving of reshaping is proposed. Primary energy demand for conventional recycling and reshaping are quantified and compared. Primary energy savings…

Al-SiC Metal Matrix Composite production through Friction Stir Extrusion of aluminum chips

Abstract The production of most mechanical component requires machining operation, thus usually implying the cut material to be wasted as scrap. Traditional recycling techniques are not able to efficiently recycle metal chips because of some critical aspects that characterize such kind of scraps (shape, oxide layers, contaminating residues, etc). Friction Stir Extrusion is an innovative solid state direct-recycling technique for metal machining chips. During the process, a rotating tool is plunged into a hollows matrix to compact, stir and finally, back extrudes the chips to be recycled in a full dense rod. This process results to be particularly relevant since no preliminary treatment of t…

A numerical model for Wire integrity prediction in Friction Stir Extrusion of magnesium alloys

Abstract A numerical model for the prediction of the wire quality produced by the novel direct machining chip recycling technique known as Friction Stir Extrusion (FSE) is presented. Wire microstructure and wire integrity have been predicted by embedding in the code the equations enabling the calculation of the Zener-Hollomon parameter as well as the W parameter of the Pivnik-Plata solid bonding criterion. The proposed model, developed for the AZ31 magnesium alloy using the commercial simulation package DEFORM, is 3D Lagrangian, thermo-mechanically coupled with visco-plastic material behavior. The model was first validated against experimental temperature measurements and then used to predi…

Deep drawing of conical and spherical thin parts utilizing a rubber punch

Shape distortion and thickness distribution during SPIF processes: experimental and numerical analysis

Single Point Incremental Forming (SPIF) is a quite new sheet forming process which offers the possibility to deform complex parts without dedicated dies using only a single point tool and a standard 3-axis CNC machine. The process mechanics enables strains much higher than traditional sheet forming processes, but particular attention must be given to the final part geometrical accuracy. In this paper the capabilities of a dedicated explicit numerical model are quantitatively analyzed on pyramid-shaped parts. In particular a comparison between experimental and numerical results is reported. Three different shapes at the varying of the stamping angle were considered and the final shape was ac…

Effect of Process Parameters on the Joint Integrity in Friction Stir Welding of Ti-6Al-4V Lap Joints

Friction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, is now being successfully used also for magnesium alloys, copper and steels. The wide diffusion the process is having is due to the possibility to weld materials traditionally considered difficult to be welded or “unweldable” by traditional fusion welding processes due to peculiar thermal and chemical material properties. Additionally, the process allows welding a wide range of sheet thickness (up to 50mm) avoiding typical fusion welding processes defects, like cavities and porosities, with no shielding gas, filling material or joint preparation. Recently, researc…

Improving Formability in SPIF Processes through High Speed Rotating Tool: Experimental and Numerical Analysis

Single-point incremental forming (SPIF) is a quite new sheet-forming process which offers the possibility to deform complex parts without dedicated dies using a single-point tool and a standard three-axis CNC machine. Although the process mechanics enables higher strains with respect to traditional sheet-forming processes, research has been focused on further increasing the maximum forming angle. In the paper, a new approach is used to enhance the material formability through a localized sheet heating as a consequence of the friction work caused by high speed rotating tool. Numerical simulation was utilized to relate the effect of temperature with the main field variables distribution in th…

Factors Influencing Bonding Mechanics in FSW of AA5754

Solid state bonding recurs in several manufacturing processes, as extrusion of hollow profiles and solid welding processes. Among the latter, Friction Stir Welding (FSW) is nowadays of particular industrial interest because of the specific advantages with respect to the classic welding technologies. Proper conditions of pressure, temperature, strain and strain rate are needed in order to get the final effective bonding. In the paper the authors compare different solid state bonding conditions obtained at the varying of the main process parameters in FSW of butt joints of AA5754 aluminum alloys. The experimental results are compared with the numerical ones from a FEM model previously develop…

Forming of aluminum foam sandwich panels: Numerical simulations and experimental tests

Abstract The forming of the completed aluminium foam sandwich (AFS) panels would determine an improvement in the manufacturing of parts and panels. In this paper the authors have investigated the formability of AFS through experiments and numerical simulations. As far as the former are concerned, commercially prepared panels have been considered and bending and stamping processes have been taken into account. In addition, FEM analyses have been developed, utilizing a porous material model following the evolution of the material density throughout the forming processes.

Dissection Properties of Ascending Thoracic Aortic Aneurysms Associated with Bicuspid and Tricuspid Aortic Valves

Fundamental Investigations on Friction Stir Knead Welding

Meshless Simulation of Friction Stir Welding

This paper encompasses our first efforts towards the numerical simulation of friction stir welding by employing a Lagrangian approach. To this end, we have employed a meshless method, namely the Natural Element Method (NEM). Friction Stir welding is a welding process where the union between the work pieces is achieved through the extremely high deformation imposed by a rotating pin, which moves between the two pieces. This extremely high strain is the main responsible of the difficulties associated with the numerical simulation of this forming process. Eulerian and Arbitrary Lagrangian-Eulerian (ALE) frameworks encounter difficulties in some aspects of the simulation. For instance, these ap…

Analysis of the mechanical performance of hybrid (SPR/bonded) single-lap joints between CFRP panels and aluminum blanks

Abstract The increasing use of innovative materials in manufacturing of modern mechanical components has led to the development of reliable joints between innovative (composite materials etc.) and traditional materials (steel, aluminum etc.). In the last few years, hybrid joints, combining the advantages of the adhesive joints and traditional mechanical joints as bolted or riveted joints, have been shown an increasing industrial interest especially in automotive and aerospace sectors. In the present paper a systematic experimental study of hybrid lap joints was carried out with the aim to detect the optimal joint configuration. Tensile tests on hybrid joints made by combining adhesive bondi…

Studio sperimentale di giunti ibridi CFRP-alluminio

FSW of lightweight aluminum structures: lap joint development

On the springback prediction in 3d sheet metal forming processes

Design of the friction stir welding tool using the continuum based FEM model

In friction stir welding (FSW), the welding tool geometry plays a fundamental role in obtaining desirable microstructures in the weld and the heat-affected zones, and consequently improving strength and fatigue resistance of the joint. In this paper, a FSW process with varying pin geometries (cylindrical and conical) and advancing speeds is numerically modeled, and a thermo-mechanically coupled, rigid-viscoplastic, fully 3D FEM analysis able to predict the process variables as well as the material flow pattern and the grain size in the welded joints is performed. The obtained results allow finding optimal tool geometry and advancing speed for improving nugget integrity of aluminum alloys.

Advancing manufacturing processes research at NAMRC 46

Research on manufacturing processes is further enriched and becomes stronger at the 46th North American Manufacturing Research Conference (NAMRC 46) at Texas A&M University, College Station, TX, USA. Manufacturing processes are tightly connected to innovation. They have been the key areas that support and influence a nation’s competitiveness and economy since the eighteenth century. As the primary driving force behind economic growth, manufacturing processes enable and facilitate innovative products realisation, ranging from heavy-duty machinery to smart home electronics. In the past centuries, they have contributed significantly to modern civilisation and created the momentum that driv…

Residual stresses in friction stir welding: numerical simulation and experimental verification

Residual stress and material flow prediction in Friction Stir Welding of Gr2 Titanium T-joints

Friction Stir Welding is nowadays an established technique successfully used by many industries. However, most of the research and, consequently, most of the applications regard aluminum alloys and butt joints. T-joints are of high interest for different industrial sectors as aeronautical, aerospace, naval and ground transportation, for which joint integrity and low residual stress are extremely important. In this study, an experimental and numerical approach is proposed with the aim to study the peculiarities of the residual stress distribution and material flow occurring in FSW of CP-Ti T-joints. Experiments were carried out to assess the feasibility of the process and to acquire the temp…

Life cycle energy and CO2 emissions analysis of food packaging: an insight into the methodology from an Italian perspective

Packaging is strictly connected to environmental issues as it is a product characterised by high material consumption rate; it is often transported over long distances and has a short life. Providing environmental analysis is, therefore, urgent to identify energy and resources efficient solutions. The paper, taking advantage of a real case study, presents a life cycle-based comparative analysis among three different food packaging systems. The paper compares the life cycle of tin steel, polypropylene and glass-based packaging of an Italian preserves producer. The analysis leads to the conclusion that, for the baseline scenario, polypropylene packaging represents the greenest solution, where…

Friction Stir Welding of Tailored Blanks: Investigation on Process Feasibility

Tailor welded blanks (TWBs) are conventionally produced by laser or traditional welding processes. In either case, the joints are created by solid-liquid-solid phase transformations that result in undesirable microstructures and tensile residual stresses detrimental to joint performance. This study investigates feasibility of an alternate joining process, friction stir welding (FSW). The joining of AA7075-T6 blanks of different thickness is investigated through FE analyses and controlled experiments. It is found that for a successful joint, the welding parameters have to be carefully designed so that the resulting metal flow and the temperature history during FSW are consistent for the two …

Joining by plastic deformation

Abstract As the scale and complexity of products such as aircraft and cars increase, demand for new functional processes to join mechanical parts grows. The use of plastic deformation for joining parts potentially offers improved accuracy, reliability and environmental safety as well as creating opportunities to design new products through joining dissimilar materials. This paper aims to provide an overview of the state of the art in such joining processes, including cold welding, friction stir welding, self-pierce riveting, mechanical clinching and joining by forming. The paper includes description of the mechanism of joint formation, and analysis of joint performance and applicability.

Caratterizzazione microstrutturale e meccanica di giunti friction skin-stringer (2024/t4-7075/t6) saldati a basso e alto apporto termico

Shape Distortion and Thickness Distribution during SPIF Processes: Expermental and Numerical Analysis

Single Point Incremental Forming (SPIF) is a quite new sheet forming process which offers the possibility to deform complex parts without dedicated dies using only a single point tool and a standard 3-axis CNC machine. The process mechanics enables strains much higher than traditional sheet forming processes, but particular attention must be given to the final part geometrical accuracy. In this paper the capabilities of a dedicated explicit numerical model are quantitatively analyzed on pyramid-shaped parts. In particular a comparison between experimental and numerical results is reported. Three different shapes at the varying of the stamping angle were considered and the final shape was ac…

Spot friction stir welding of aluminum alloys

FSW lap joint resistance optimization through gradient techniques

In the recent years the scientific interest on Friction Stir Welding (FSW) has grown more and more since such joining technique allows to weld light weight alloys rather difficult to be welded or even “un-weldable” with the classic fusion welding operations. What is more, a few industrial applications of the process are already known in different manufacturing fields. In the paper the optimization problem of a FSW lap joint for automotive applications is investigated taking into account process parameters such as the tool rotating speed and the tool feed rate; a numerical gradient technique is applied for the optimization procedure reducing the number of experimental tests to be developed.

Ottimizzazione di Giunti Ibridi(Spr/Incollati) Gfrp-Al

Springback effect evaluation in three-dimensional stamping processes at the varying of blankholder force

The quantitative evaluation of elastic springback in sheet metal stamping processes is still today a very interesting research topic, since this phenomenon causes a manufacturing shape defect. A measurement technique based on the shadow moiré method, already developed by the present authors, has been further upgraded and applied to evaluate the springback phenomenon in the deep drawing of square boxes, the basic three-dimensional stamping process. In particular this technique is able to determine the final lateral surface of the drawn parts, once extracted from the dies, and to compare such surface with the ideal one derived from the die's computer-aided design (CAD) geometry. Proper quant…

An Optical Technique for Springback Measurement in Axisymmetrical Deep Drawing Operations

Abstract In this paper, a measurement technique based on the shadow moire method has been set up to evaluate the springback phenomenon in deep drawing operations. Two proper coefficients are introduced to quantitatively describe the investigated effect. In particular, the proposed technique is able to acquire the final profile of the drawn parts along one or more lateral contour, once extracted out from the dies, and compare such profile with the ideal one derived from the dies CAD geometry. The proposed technique has been applied to an axisymmetrical deep drawing operation, and, moreover, the influence of the blankholder force level and lubricating conditions has been taken into account. T…

On the Effectiveness of SPIF Process to Re-Form End-of-Life Components as Compared to Conventional Forming Approach

Manufacturing processes have a significant impact on global energy consumptions. The recovery of materials and functions for the implementation of the Circular Economy principle needs to be focused on either, by utilizing new techniques or the rethinking of old processes to rework End-of-life (EoL) components. Previous researches have shown Single Point Incremental Forming (SPIF) process as a good alternate for sheet metal EoL components reuse by their reshaping. In this article, the authors aim to study the effectiveness of the SIPF processes by comparing its reshaping performance with other, more conventional forming processes. An initial deep drawing process was performed to imitate alum…

NAMRC 49 Fast-Tracked Research Papers to Journal of Manufacturing Systems and Journal of Manufacturing Processes

Modelling Aspects in Accumulative Roll Bonding process by Explicit Finite Element Analysis

Accumulative Roll-Bonding (ARB) process is a severe plastic deformation (SPD) process, capable of developing grains below 1 μm in diameter and improving mechanical properties of the material. In this study, the authors compared two different FE-codes with respect of its applicability for numerical analysis of the ARB process. Modelling this process was achieved using the explicit code for Abaqus/CAE both in 2D and 3D. The proposed model was used to assess the impact of ARB cycles on the final material properties. The numerical results in 2D and 3D were compared and contrasted. The research work presented in this paper is focused on the simulation optimization based on CPU time minimization.…

Self-piercing riveting for aluminium alloys-composites hybrid joints

In the paper, the growing interest on hybrid joints developed between composite panels and aluminium alloys blanks is focused. The self-piercing riveting operation is considered and its feasibility for the proposed joints verified. The most relevant process parameters were investigated in order to determine a suitable process window and, what is more, the mechanical performances of the developed joints were investigated in order to determine process parameters aimed to maximise them. Finally, the failure mechanics of the obtained joints were considered in order to highlight the mechanisms which occur and determine the lost of the load carrying capability of the joints. The developed experim…

Process Mechanics in Friction Stir Welding of Magnesium Alloys: Experimental and Numerical Analysis

A thermo-mechanical model for the simulation of the Friction Stir Welding process

Numerical simulation of Friction Stir Welding of Ti-6Al-4V Titanium alloys

On the fem simulation of FSW and LFW operations

Recent advances in sheet metal single point incremental forming and friction stir welding

A technical note on an experimental device to measure friction coefficient in sheet metal forming

Abstract In the paper the authors present the results of several experimental tests aimed to determine the Coulomb friction coefficient in sheet metal forming operations at the varying of the sheet metal material and for different operative conditions. In particular a few pressure and lubricating conditions have been investigated. In order to develop such experiments a dedicated fixture was designed and set-up starting from the one proposed by Wilson.

On the influence of tool path in friction stir spot welding of aluminum alloys

Abstract Friction stir spot welding (FSSW) has been proposed as an effective technology to spot weld the so-called “difficult to be welded” metal alloys. In the paper, a variation of the FSSW process has been considered. A tool path is given after the sinking phase nearby the initial penetration site; in this way a larger welding spot is obtained and more material is involved in the bonding process. The process mechanics of such modified FSSW process is highlighted and the joint strength undergoing tensile tests is considered at the varying both of the assigned tool path and of a few process parameters. Macro- and micro-analyses are made in order to analyze the local material microstructure…

Fatigue strength of a single lap joint SPR-bonded

In the last years, hybrid joints, meaning with this the joints which consist in combining a traditional mechanical joint to a layer of adhesive, are gradually attracting the attention of various sectors of the construction of vehicles and transportation industries, for their better performance compared to just mechanical joints (self-piercing riveting SPR, riveting, and so on) or just to bonded joints. The paper investigates the fatigue behavior of a single lap joint self-piercing riveted (SPR) and bonded throughout fatigue tests. The considered geometric configuration allowed the use of two rivets placed longitudinally; an epoxy resin was used as adhesive. In the first part of the work sta…

Energy demand reduction of aluminum alloys recycling through friction stir extrusion processes implementation

Abstract Aluminum alloys are characterized by high-energy demands for primary production. Recycling is a well-documented strategy to lower the environmental impact of light alloys production. Despite that, conventional recycling processes are still energy-intensive with a low energy efficiency. Also, permanent material losses occur during remelting because of oxidation. Recently, several solid-state recycling approaches have been analyzed; in fact, by avoiding the remelting step both energy and material can be saved and, therefore, the embodied energy of secondary production can be substantially reduced. In this paper, the solid-state approach Friction Stir Extrusion (FSE) is analyzed for a…

Fatigue life of AA2024-T4 friction stir welded joints influence of process parameters and post-welding treatments

Friction Stir Welding of 3D Industrial Parts: Joint Strength Analysis

In the recent years Friction Stir Welding (FSW) has become an important joining technique since it allows to weld light weight alloys rather difficult to be welded or even “un-weldable” with the classic fusion welding operations. In the paper the authors present the application of the FSW process to the joining of 3D complex shapes typical of the industrial environment. In particular the research was aimed to highlight the joint mechanical strength at the varying of the 3D geometry of the welding line.Copyright © 2006 by ASME

The evaluation of springback in 3D stamping and coining processes

Abstract An effective predictive technique of the elastic springback in a fully 3D 90° V-punch V-die bending process is presented. This is based on a combined approach in which an explicit finite element code was used to simulate the loading phase of the process whilst an implicit procedure was used to analyse the springback phase. Two different punches with a nose radius of 4 and 8 mm were used. An increase in the springback ratio with the coining load was observed with the lower nose radius. Conversely, an increase in the springback ratio with the coining load up to a peak value (>1), corresponding to a force of about 20 kN, followed by a decrease in the springback ratio with increasing t…

Factors Influencing Bonding Mechanics in FSW of AA5754

The application of AI techniques in the optimal design of multi-pass cold drawing processes

Abstract In the paper the problem of optimal pass schedule design in multi-pass wire drawing process is investigated. An automatic design procedure based on an effective artificial intelligence (AI) technique, namely simulated annealing (SA), is proposed. The developed algorithm is aimed to achieve a satisfactory balance of the drawing stresses on the material along the reduction sequence, maintaining in the meantime the drawing stress at each pass below a safety value. In this way both the optimal number of passes and the optimal drawing sequence are determined. The effectiveness of the design procedure is tested through the comparison of the sequences suggested by the algorithm with a set…

Uncovering Technological and Environmental Potentials of Aluminum Alloy Scraps Recycling Through Friction Stir Consolidation

Conventional metal chips recycling processes are energy-intensive with low efficiency and permanent material losses during re-melting. Solid state recycling allows direct recycling of metal scraps into semi-finished products. It is expected that this process category would lower the environmental performance of metals recycling. Friction Stir Consolidation is a new solid-state technique taking advantage of friction heat generation and severe plastic deformation to consolidate chips into billets. In this research, the feasibility of Friction Stir Consolidation as aluminum chips recycling process is analyzed. Specifically, an experimental campaign has been carried out with varying main proces…

Stato dell’arte del Friction Stir Welding

Special Issue of Journal of Manufacturing Processes on Advancing Manufacturing Processes Research at NAMRC 46

During the refereeing process of papers submitted to NAMRC 46 this year, nine high-quality papers have been selected and fast-tracked to a special issue of Journal of Manufacturing Processes (JMP) entitled “Advancing Manufacturing Processes Research at NAMRC 46”. The selection of the fast-track papers was based on authors’ preferences, quality of the papers, reviewers’ recommendations, Track Chairs’ picks, pre-selection by the Chair of NAMRI/SME Scientific Committee, and final approval by the JMP Editor. The nine papers published in JMP are therefore excluded from the Proceedings of NAMRC 46 in Procedia Manufacturing. Nevertheless, these papers are presented in person at NAMRC 46. Details o…

Bonding prediction in friction stir consolidation of aluminum alloys: A preliminary study

Friction Stir Consolidation (FSC) is a solid-state process that results in consolidation of metal powders or chips producing solid billet through severe plastic deformation and the solid-state bonding phenomena. This process can be used both for primary production and for metal scrap recycling. During the FSC process, a rotating die is plunged into a hollow chamber containing the finely divided, unconsolidated material to be processed. In this paper, a FEM numerical model for the prediction of the quality of the consolidated billet is presented. In particular, a dedicated bonding criterion that takes into account the peculiar process mechanics of this innovative technology is proposed.

Fatigue behaviour of self-piercing riveting of aluminium blanks and carbon fibre composite panels

In this article, the fatigue behaviour of self-piercing riveted joints in 2024-T6 aluminium sheets and carbon fibre composite panels is studied through experimental tests and numerical simulations. This study, aimed to evaluate the best process conditions and the mechanical behaviour of the joint itself, can be divided into few phases: the first one in which the static mechanical behaviour was investigated in order to evaluate the best process conditions (such as the best value of oil pressure of the riveting system) and the second one which had the purpose to determine the fatigue behaviour of the joint. Finally, a finite element method analysis of the riveting process was developed in or…

Mechanical and microstructural properties prediction by artificial neural networks in FSW processes of dual phase titanium alloys

Abstract Friction Stir Welding (FSW), as a solid state welding process, seems to be one of the most promising techniques for joining titanium alloys avoiding a large number of difficulties arising from the use of traditional fusion welding processes. In order to pursue cost savings and a time efficient design, the development of numerical simulations of the process can represent a valid choice for engineers. In the paper an artificial neural network was properly trained and linked to an existing 3D FEM model for the FSW of Ti–6Al–4V titanium alloy, with the aim to predict both the microhardness values and the microstructure of the welded butt joints at the varying of the main process parame…

Influence of parameters in a hybrid joint (SPR/bonded) GFRP-aluminum

Special Issue of Journal of Manufacturing Processes on New Trends in Manufacturing Processes Research

Special issue of journal of manufacturing processes on new trends in manufacturing processes research

On the numerical simulation of FSW processes

On the Finite Element Simulation of Secondary Operations on Metallic Foams

Metallic foams have been recently introduced also as industrial materials due to their well known advantages. In fact, their low mass in conjunction with the good thermal and mechanical properties push toward an extensive diffusion in manufacturing industry. In the study here addressed, a very accurate investigation concerning the latter two aspects has been carried out. In fact, a secondary manufacturing process, i.e. the foam bending, has been taken into account. Anyway, all the knowledge derived for sheet metal bending is not directly applicable to the foams. A finite element code has been utilized for modeling the foam behavior during the bending processes and an accurate material rheol…

Design Of Experiments for the optimization the process parameters of thixotropic aluminum alloy

The success of the thixoforming process depends on the possibility to confer to material, when it is found in the semisolid state, a microstructure characterized by globular particles of solid phase surrounded by a continuous film of liquid phase; such microstructure is obtainable through particular thermo-mechanical treatments. In the present research, in order to optimize the influence of process parameters in the step in which the thixotropic properties are conferred to the AA7075 aluminum alloy, the statistic technique of the Design Of Experiments (DOE) has been used. The advantages in the application of such technique are expressible in terms of reduction the times of development of pr…

Wear Analysis During Friction Stir Processing of A359+20%SiC MMC

Metal Matrix Composites (MMC) are very interesting materials for applications in the automotive and aerospace fields, since they combine the lightness of Aluminium with the strength of the ceramic reinforcement. These materials are very difficult to join and conventional welding techniques are not applicable, whereas solid-state welding techniques, like Friction Stir Welding (FSW), could be a solution. However very hard tool materials will need to be chosen in order to overcome the problem of heavy abrasive tool wear. In this work the wear behaviour of coated and uncoated steel tools has been investigated in the Friction Stir Processing of extruded bars in A359 + 20%SiC. AISI 1040 steel was…

Process mechanics analysis in single point incremental forming

The request of highly differentiated products and the need of process flexibility have brought the researchers to focus the attention on innovative sheet forming processes. Industrial application of conventional processes is, in fact, economically convenient just for large scale productions; furthermore conventional processes do not allow to fully satisfy the mentioned demand of flexibility. In this contest, single point incremental forming (SPIF) is an innovative and flexible answer to market requests. The process is characterized by a peculiar process mechanics, being the sheet plastically deformed only through a localised stretching mechanism. Some recent experimental studies have shown …

On the improvement of material formability in SPIF operation through tool stirring action

Single-point incremental forming (SPIF) is a quite new sheet-forming process which offers the possibility to deform complex parts without dedicated dies using a single-point tool and a standard three-axis CNC machine. The process mechanics enables higher strains with respect to traditional sheet-forming processes, but particular attention must be given to the maximum forming angle. In this paper, a new approach is proposed to enhance the material formability through a localized sheet heating as a consequence of the friction work caused by elevated tool rotational speeds. AA1050-O, AA1050-H24, and AA6082-T6 were utilized, and the reached temperatures were recorded by thermocouples, fixed to …

Phase evolution in hot forging of dual phase titanium alloys: Experiments and numerical analysis

Abstract Modern aeronautical and aerospace industries must face the demanding challenge of reducing operational consumption and production costs coming from materials and labor. Current trend of engineering is oriented to meet both requirements increasing the use of materials characterized by high specific resistance as titanium alloys. Hot forging can be used to reduce the production costs of titanium components: forging in closed dies of billets or semi-finished forms, at different temperatures above or below the β-transus temperature, allows the production of complex shapes with limited amount of edge trim removal and machining rework after forging. Unfortunately, as far as Ti–6Al–4V tit…

Material flow analysis in dissimilar friction stir welding of AA2024 and Ti6Al4V butt joints

The complex material flow occurring during the weld of dissimilar AA2024 to Ti6Al4V butt and lap joints was highlighted through a dedicated numerical model able to take into account the effects of the different materials as well as the phase transformation of the used titanium alloy.

New trends in manufacturing systems research

Editorial

On the Solid Bonding Phenomena in Linear Friction Welding and Accumulative Roll Bonding Processes: Numerical Simulation Insights

Solid Bonding based welding processes allow to obtain defect free joints with low residual stress and low distortion. However, the engineering and optimization of solid bonding processes is difficult and requires a large number of time and cost consuming test trials. In this way, proper numerical models are essential tools permitting effective process design. The aim of this research was the comparison of the material process conditions during two different manufacturing processes taking advantage of the same metallurgical phenomenon, namely solid bonding. Linear Friction Welding, used to weld non-axisymmetric components and Accumulative Roll Bonding, used to increase the mechanical propert…

Multi-material based functionally graded billets manufacturing through friction stir consolidation of aluminium alloys chips

New deal of Friction Stir Consolidation (FSC) is its evolution from Recycling technique towards Upcycling. In this paper, the potential of FSC to manufacture Functionally Graded billets is proved. Processing chips of two different aluminium alloys (AA7075, AA2011-T3), graded hardness distributions were obtained along the longitudinal direction of the manufactured billet. Material flow was analysed by EDX analyses and numerical simulations; mechanical properties were assessed through hardness measurements. The influence of material's position, mass fraction of each material and process parameters was considered. Results reveal that FSC offers a proper control in the design of billets with gr…

In-process tool force and rotation variation to control sheet thickness change in friction stir welding of magnesium alloys

Two different in-process control strategies, developed in order to produce sound joints in AZ31 magnesium alloy by Friction Stir Welding on sheet blanks with a non-uniform thickness, are presented and compared. To this purpose, sheets with dip or hump were machined and welded by either changing the rotational speed or the tool plunging in order to keep constant the vertical force occurring during welding. The mechanical strength of the joints was measured in the zones where the sheets before welding were characterised by different thicknesses. The sheets welded by the two different strategies are characterized by very similar ultimate tensile strength values. Finally, the results showed tha…

New trends in manufacturing processes research

Research on manufacturing processes is further enriched and becomes stronger at the 47th North American Manufacturing Research Conference (NAMRC 47) at Penn State University, The Behrend College, Erie, Pennsylvania USA. Innovation is fundamentally connected to products or processes: the former being rarer and more difficult to be obtained, the latter is definitively related to economy, competitiveness and welfare of a nation. Furthermore, the research and success in innovation of processes permit also the proposition of innovative products. Manufacturing processes engineering is of primary interest for industries and new challenges are faced every day in order to reduce costs, increase comp…

On the friction stir welding of titanium alloys: Experimental measurements and FEM model fine tuning

Friction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, is now being successfully used also for magnesium alloys, copper and steels. Recently, research is focusing on titanium alloys thanks to the high interest that such materials are getting from the industry as welding of titanium alloys by traditional fusion welding techniques presents several difficulties due to high material reactivity resulting in bonding with oxygen, hydrogen, and nitrogen with consequent embrittlement of the joint. In this way FSW represents a cost effective and high quality solution. The study of the temperatures reached at the varying of the …

Springback evaluation in fully 3-D sheet metal forming processes

Abstract In the modern manufacturing industries the knowledge and proper control of the sheet metal springback after forming is a fundamental aspect in the achievement of near net shape stamped parts. In this paper an effective springback prediction in some fully three-dimensional stamping processes is carried out. Such a prediction is based on a combined approach in which an explicit finite element code has been employed to simulate the forming phase while a traditional implicit procedure has been used to analyse the springback phase. The results obtained have been compared with a set of experimental tests and an excellent correlation between the predicted and experimental data has been fo…

Analytical bonding criteria for joint integrity prediction in friction stir welding of aluminum alloys

Abstract In this study, two bonding criteria, previously used for porthole die extrusion, are applied to FSW starting from the local value of the main field variables calculated through a specifically developed 3D numerical model of the process. Their applicability and effectiveness have been assessed through an experimental and numerical campaign carried out with the main process parameters varying in a wide range. The pressure–time–flow criterion was demonstrated to be better suited for FSW processes when large welding speed is used.

Dissimilar titanium-aluminum skin-stringer joints by FSW: process mechanics and performance

Ever since its inception, friction stir welding (FSW) is being validated by scientific investigations as an effective substitution for fusion-based conventional joining technologies. One of the main strengths of FSW is the possibility to produce dissimilar joints, even using materials extremely different in terms of thermal and mechanical properties. The goal of the present research is to investigate the feasibility of both Al-Ti skin-stringer and reversed Ti-Al skin-stringer joints, highlighting the effect of joint configuration and main process parameters on material flow and joint mechanical properties. During the investigation, the essentiality of the proper heat input through balancing

Life Cycle Assessment of aluminum alloys chips recycling through single and multi-step Friction Stir Consolidation processes

Manufacturing scientists have to find new processes enabling energy and resource efficient circular economy strategies. Solid state recycling processes have proved to be environmentally friendly alternatives to recycle aluminum alloys process scraps like chips. In this paper the environmental characterization of a solid state recycling process named Friction Stir Consolidation (FSC) is presented. A full Life Cycle Assessment (LCA) comparative analysis is developed: the environmental performance of new and different variants of FSC processes and remelting based routes are quantified and compared to one another. Also, different scenarios are analysed to provide guidelines for the correct impl…

Study of forming mechanics of magnetic field–assisted single point incremental forming

This paper describes the forming characteristics and mechanics of magnetic field–assisted single point incremental forming (M-SPIF) in which an Nd-Fe-B magnet ball tool is placed on top of a piece of sheet metal and is driven by an Nd-Fe-B magnet placed below the workpiece. To gain an understanding of the force mechanics that power M-SPIF, the tool motion and forming force were experimentally analyzed. In M-SPIF, the forming force is applied multi-directionally, and the resultant force direction is nearly colinear with the polarity of the permanent magnet ball tool. This suggests that the forming characteristics in M-SPIF may be controllable by controlling the magnetic polarity of the tool.

Weld quality prediction in linear friction welding of AA6082-T6 through an integrated numerical tool

Abstract A numerical and an experimental campaign were carried out with varying oscillation frequency and interface pressure. The local values of the main field variables at the contact interface between the specimens were predicted by a Lagrangian, implicit, thermo-mechanical FEM model and used as input of a dedicated Neural Network (NN). The NN, integrated in the FEM environment, was designed in order to calculate both a Boolean output, indicating the occurrence of welding, and a continuous output, indicating the quality of the obtained solid state weld. The analysis of the obtained results allowed three different levels of bonding quality, i.e., no weld, sound weld and excess of heat, to…

Rubber Forming Processes of Thin Sheets

In the last decade flexible media have been increasingly utilized in sheet metal drawing processes in order to reduce the tooling cost and to improve the product quality. In the present paper an axisymmetric deep drawing process of thin steel sheets is taken into account: in particular a flexible pad is utilized in order to simplify the tooling set. The process mechanics is investigated through numerical simulations and experimental tests with the aim to find out a proper set of operative parameters allowing the stamping of sound components and to highlight the particular deformation path of the drawing cup. The comparison between the numerical predictions and the experimental verification …

Process parameters analysis in friction stir welding of AA6082-T6 sheets

On the Solid Bonding Phenomena in Linear Friction Welding and Accumulative Roll Bonding Processes: Numerical Simulation Insights

Solid Bonding based welding processes allow to obtain defect free joints with low residual stress and low distortion. However, the engineering and optimization of solid bonding processes is difficult and requires a large number of time and cost consuming test trials. In this way, proper numerical models are essential tools permitting effective process design. The aim of this research was the comparison of the material process conditions during two different manufacturing processes taking advantage of the same metallurgical phenomenon, namely solid bonding. Linear Friction Welding, used to weld non-axisymmetric components and Accumulative Roll Bonding, used to increase the mechanical propert…

Friction stir welding of dissimilar aluminium– magnesium joints: Sheet mutual position effects

Friction stir welding (FSW) is a solid state welding process used to weld difficult to be welded or unweldable materials as aluminium alloys. In the last years, other materials have been successfully tested as magnesium, titanium and nickel based alloys. Dissimilar joints can be obtained by FSW, but issues arise concerning the correct choice of the process parameters. In the paper, the results of an experimental and numerical campaign aimed to produce dissimilar AZ31-AA6016-T6 butt joints are presented. The effect of sheet mutual position and main process parameters was investigated. It was found that intermetallics are the main cause of the poor quality of the joints. Sound joints can be p…

In-process heat treatments to improve FS-welded butt joints

Friction-stir welding (FSW) is a relatively new but already well known solid-state welding process whose main advantage with respect to fusion welding processes is the possibility to successfully weld light alloys, traditionally considered difficult to weld or unweldable. Despite the good mechanical performances that can be obtained, there exists the possibility to further improve the joints' effectiveness through post-welding heat treatments that are however time and cost-expensive and, therefore, not best suited for industrial applications. In the present paper, the authors report the results of an experimental campaign, developed on FSW of AA7075-T6 aluminum alloy, aimed to investigate t…

Thermal and thermo-mechanical treatments on shape memory alloys

Mechanical and metallurgical properties of titanium alloy friction stir welded butt joints

Microstructural Changes Determining Joint Strength in Friction Stir Welding of Aluminium Alloys

In the paper the results of a wide experimental activity on friction stir welding (FSW) of aluminum alloys are reported. In particular the butt joints of two different materials, namely AA1050-O and AA6082-T6 were considered. Grains dimensions and precipitates density were investigated both in the parent materials and after the welding processes. Furthermore post-welding heat treatments effects on the joint strength were studied.

Numerical Prediction Of Elastic Springback In An Automotive Complex Structural Part

Friction Stir Knead Welding of steel aluminium butt joints

To develop steel aluminium-tailored hybrids in a butt joint for sheets in a thickness of about 1 mm conventional Friction Stir Welding is not feasible due to a high distortion of the welded specimen. Contrary to Friction Stir Welding the tool used for Friction Stir Knead Welding has no pin wherefore higher welding speeds can be realised. Due to the fact that this is a newer process, applied for patent in 2005, the cut contours of the edges and their variations have to be optimised by numerical analysis to transfer a maximum of load in order to improve the formability. The examined materials in this paper are steel DC04, as well as the aluminium alloys AA5182 and AA6016 in sheet thicknesses …

Solid state bonding in extrusion and FSW: process mechanics and analogies

Abstract The solid state bonding occurring in extrusion and in friction stir welding (FSW) processes is investigated through FEM models previously developed and validated. In particular, for the AA6082-T6 aluminum alloys, the most relevant field variables have been monitored and compared, such as strain, strain rate, effective stress and pressure. The aim of the research is the development of an effective FSW bonding criterion.

Constant Heat Input Friction Stir Welding of Variable Thickness AZ31 Sheets Through In-Process Tool Rotation Control

Tailored blanks characterized by variable thickness were friction stir welded (FSWed) with the aim to obtain constant joint properties along the weld seam, regardless of the thickness change. To pursue this goal, the heat input was kept constant by in-process control of tool rotation. A dedicated numerical model of the process was used to determine the tool rotation values as a function of the sheet thickness. The mechanical properties and the microstructure of the FSWed joints, produced with varying process parameters, were studied. It was found that the proposed approach can produce joints with uniform properties along the weld line in terms of stress–strain curve shape, joint strength, e…

Microstructural, mechanical and energy demand characterization of alternative WAAM techniques for Al-alloy parts production

Abstract Additive manufacturing (AM) processes are gathering momentum as an alternative to conventional manufacturing processes. A research effort is being made worldwide to identify the most promising AM approaches. Within this category, wire arc additive manufacturing (WAAM) is among the most interesting, especially when large parts must be manufactured. In this paper, two different WAAM deposition techniques suitable for the deposition of Aluminum alloys, Cold Metal Transfer (CMT) and CMT mix drive, are analyzed and compared. With the aim of obtaining a clear picture concerning the two different techniques, microstructural analyses, mechanical property evaluation and electrical energy de…

Friction Stir Welding of Ti6Al4V complex geometries for aeronautical applications: a feasibility study

Abstract While Friction Stir Welding (FSW) of aluminium alloys can be considered a mature technology, even for complex joint morphologies, as T joints welded “in transparency”, welding of hard material still presents several open issues. In fact, welding of titanium alloys is a challenging process due to the chemical, mechanical and thermal characteristics of such materials which are subjected to atmosphere contamination resulting in joint hydrogen, oxygen and nitrogen embrittlement; additionally, due to the high melting temperature, large distortion and residual stress are found in joints obtained by traditional fusion welding processes as gas metal arc welding, electron beam welding and l…

Influence of mechanical properties of the sheet material on formability in single point incremental forming

Abstract New trends in sheet metal forming are rapidly developing and several new forming processes have been proposed to accomplish the goals of flexibility and cost reduction. Among them single point incremental forming operations, in which the final shape of the component is obtained by the relative movement of a simple and small punch with respect to the blank, appear quite promising. In the paper, material formability issues in incremental forming were studied. Some relevant correlations among material formability and other mechanical properties of the material were analysed. The FLD 0 value, i.e. the major strain at fracture in plane strain conditions, was determined for different mat…

Behaviour of friction stir welded T-components under loading

Friction Stir Welding of AA6082-T6 T-joints: Process Engineering and Performance Measurement

In the paper the authors present the results of a wide range of experiments on T-parts. First, friction stir welding process engineering has been developed with the aim of determining the specific process parameters that make up the soundness of the obtained T-parts. Then the performance of the obtained T-joints has been compared with T-joints obtained by metal inert gas welding and extruded T-parts. The parts have been tested utilizing a customized bending test with the aim of highlighting their behaviour both in elastic and plastic fields.

An insight into the electrical energy demand of friction stir welding processes: the role of process parameters, material and machine tool architecture

The manufacturing sector accounts for a high share of global electrical energy consumption and CO 2 emissions, and therefore, the environmental impact of production processes is being more and more investigated. An analysis of power and energy consumption in friction stir welding processes can contribute to the characterization of the process from a new point of view and also provide useful information about the environmental impact of the process. An in-depth analysis of electrical energy demand of friction stir welding is here proposed. Different machine tool architectures, including an industrial dedicated machine, have been used to weld aluminum and steel sheets under different process …

On the Joining of Aluminum Foams and Aluminum Foam Sandwiches

Coupled thermo-mechanical-metallurgical analysis of an hot forging process of titanium alloy

Physico-chemical characterization and corrosion properties of friction stir welded Al2024-T4 alloys

Beta-forging of Ti6Al4V titanium alloy powders consolidated by HIP: Plastic flow and strain-rate relation

Ti6Al4V is probably the best known and studied titanium alloy, not only for aerospace applications. Nevertheless the deformation behavior still represents a challenge if any modification in the deformation process is required or introduced. This work deals with deformation behavior description of Ti6Al4V HIPped powders during high temperature deformation tests carried on in the Beta-region. Laboratory compression and tensile tests have been coupled with relaxation tests in order to achieve robust data about strain rate sensibility m-coefficient and activation energy Q. These results have been fitted for the assessment of a more general exponential deformation law. The final result is a “Dor…

Analysis of the joint strength in FSW of AA7075-T6 butt joints

Dissimilar Al/steel Friction stir welding lap joints for automotive applications

A widespread usage of aluminum alloys for the fabrication of car-body parts is conditional on the employment of appropriate welding methods, especially if dissimilar welding must be performed with automotive steel grades. Dissimilar welding of aluminum alloys and steel grades poses some issues concerning the formation of brittle intermetallic compounds, difference in physical and chemical properties of the parent metals, and poor wetting behavior of aluminum. Friction stir welding is considered to be a reasonable solution to obtain sound aluminum/steel joints. A study on the join quality of dissimilar lap joints of steel and aluminum alloy sheets after friction stir welding is proposed here…

AA6082-T6 Friction Stir Welded Joints Fatigue Resistance: Influence of Process Parameters

In the paper the results of a wide range of experiments on friction stir welding (FSW) of aluminium alloys are reported. In particular, the AA6082-T6 butt joints fatigue resistance was investigated by varying the most relevant process parameters. In addition, a revolutionary pitch was utilized in order to investigate the effects of the tool rotating speed and the tool feed rate. Observations of the fracture insurgence were developed for different levels of applied load.

Continuous dynamic recrystallization phenomena modelling in friction stir welding of aluminium alloys: A neural-network-based approach

The current paper focuses on the continuous dynamic recrystallization phenomena (CDRX) occurring in friction stir welding processes of AA6082 T6 aluminium alloys. In particular, in order to predict the average grain size, a properly trained neural network is linked to the finite element method (FEM) model of the process. The utilized net, which takes as inputs the local values of strain, strain rate, and temperature, was trained starting from experimental data and numerical results. The obtained results show the capability of the artificial intelligence (AI) technique in conjunction with the FE tool to predict the final microstructure in the joint section.

Friction Based Solid State Welding Processes

In the last decade the industrial use of solid state welding processes based on frictional forces work decaying into heat is continuously increasing due to their strong advantages with respect to traditional fusion techniques. Several advances have been proposed by the scientific community regarding process mechanics, material flow and also the computer aided engineering of the operation with the aim to maximize the mechanical performances of the welded joints. In the paper Friction Stir Welding (FSW) and Linear Friction Welding (LFW) operations are considered and a review of the most relevant research issues and results is provided.

Tecniche di giunzione per la realizzazione di giunti misti acciaio-alluminio

FSW research activity at OSU and UNIPA

Development of Diamond Sawblades for granite sawing on pendulum-like-frames

Material Flow in FSW of AA7075 - T6 butt joint: numerical simulations and experimental verifications

Friction stir welding (FSW) has reached a large interest in the scientific community and in the recent years also in the industrial environment, owing to the advantages of such solid state welding process with respect to the classic ones. Advanced finite element method tools are needed in order to develop an effective engineering of the processes; quantitative results can be acquired from numerical simulations once the basic information such as the material flow is certain. A 3D Lagrangian implicit coupled rigid viscoplastic model has already been developed by the authors to simulate FSW of butt joints. In the present paper the material flow in the FSW of AA7075–T6 butt joints is investigat…

Design of the Tube Roll Forming Process Through an Heuristic Algorithm

In the paper the design of an industrial tube roll forming process is developed utilizing an heuristic algorithm, namely the simulated annealing (SA). In particular both the number and the shape of the deforming rolls are determined in order to define the forming sequence. The effectiveness of the results supplied by the SA algorithm is verified both by means of some experiments tests carried out on an industrial tube roll forming equipment and through a set of numerical simulations of the process.

Incremental forming of friction stir welded taylored sheets

In the last decade sheet metal forming market has undergone substantial mutations since the development of more efficient strategies in terms of flexibility and cost reduction is strictly due. Such requirements are not consistent with traditional metal stamping processes which are characterized by complex equipment, capital and tooling costs; thus the industrial application of such processes is economically convenient just for large scale productions. For this reason most of the research work developed in the last years has been focused on the development of new sheet forming processes able to achieve the above discussed goals. Contemporary, with particular reference to the automotive indus…

A simple experiment to characterize material formability in tube hydroforming

Abstract In tube hydroforming processes an internal fluid pressure is utilized to form the material on a properly shaped die; during the process the material axial movement is favoured by the axial feeding of an active punch. In the paper a simple experiment is presented aimed to investigate the influence of the main process variables on material formability. This equipment has enabled an extensive experimental investigation; furthermore a numerical analysis based on the finite element technique has been performed and a ductile fracture criterion has been implemented to predict the insurgence of bursting defects.

Development of corner fillet joints using friction stir welding

ANALISI DI GIUNTI A DOPPIA SOVRAPPOSIZIONE GFRP-ALLUMINIO INCOLLATI E BULLONATI

Sheet metal forming of titanium blanks using flexible media

Abstract Sheet metal forming processes using flexible media are increasingly utilized in the industrial practice due to the relatively low tooling cost. In the present investigation, a rubber forming process is applied to the manufacturing cycle of a titanium alloy component for acoustic tweeters. The proposed process allows a reduction in manufacturing costs and production time since it permits the elimination of some joining operations. The FEM analysis has permitted the definition of the optimal process parameters and tooling geometry. Accordingly, several components have been produced; the achieved quality level is comparable with the one obtained utilizing the conventional technology a…

Advancing manufacturing systems research at NAMRC 46

Research on manufacturing systems is further enriched and becomes stronger at the 46th North American Manufacturing Research Conference (NAMRC 46) at Texas A&M University, College Station, TX, USA. Advancing manufacturing systems is more prevalent than before due to recent industrial revolution (or Industry 4.0), continuous business decentralisation and needs for better overall resource efficiency and effectiveness. Manufacturers are competing in a global, dynamic marketplace that demands excellence in quality and service, throughput, innovativeness, agility in production, short response time to changing markets, and tight profitable margins. In the 21st century, manufacturing will be g…

New trends in Manufacturing Systems Research 2020.

Material Flow in FSW of T-joints: Experimental and Numerical Analysis

In the paper the authors present the results of both an experimental and a numerical campaign focused on the analysis of the occurring material flow in the FSW of T joints of aluminum alloys. In particular to investigate the metal flow experimental tests and observations has been developed utilizing a thin foil of copper as marker placed between the skin and the stringer. In this way, the actual metal flow occurring during the FSW of T-joints has been highlighted together with the real bonding surface. The acquired information is definitively useful in order to choose effective set of process parameters, improving the process mechanics and avoiding the insurgence of defects.

On the material flow in fsw of T-joints: influence of geometrical and tecnological parameters

Friction stir welding (FSW) now definitively reached a large interest in the scientific community and what is more in the industrial environment, due to the advantages of such solid state welding process with respect to the classic ones. The latter aspects are relevant also with reference to joints characterized by a complex geometry. What is more, advanced FEM tools permit to develop effective engineering of the processes; quantitative results can be acquired from numerical simulations once basic information, as the process mechanics and the material flow, are certain. Material flow plays a fundamental role in FSW since it determines the effectiveness of the joints or, in turn, the insurge…

Valutazione della vita a fatica di giunti complessi saldati tramite Friction Stir Welding

Tool Geometry in Friction Stir Welding of Magnesium Alloy Sheets

Friction Stir Welding (FSW) has been arousing a continuously increasing interest among joining processes since its invention in 1991. Although mainly used for aluminum alloys, it can also be applied to other light alloys. In the present work, experimental and numerical campaigns have been performed with the aim to study the effect of the tool geometry on the mechanical properties of FSW-ed AZ31 magnesium alloy sheets. The results, presented in terms of tensile strength, ductility, micro-hardness values and numerical field variables distributions, allow to reach a deeper knowledge on the behaviour of such relatively new material when FSW-ed, and can be used for a full optimization of the joi…

Infra-red measurement of temperature during the Friction Stir Welding process and correlation with numerical simulation

Special Issue of Journal of Manufacturing Systems on New Trends in Manufacturing Systems Research

Special issue of journal of manufacturing systems on new trends in manufacturing systems research

La simulazione numerica per la progettazione dei processi di formatura delle lamiere: Piegatura mediante rulli (roll forming)

Friction Stir Processing of NiTi Shape Memory Alloy: Microstructural Characterization

Shape Memory Alloys (SMA) are metal materials that, after being strained, come back to their original shape at a designated temperature. Welding NiTi alloys is not simple because when the material is melted, due to the high reactivity of the alloy elements, the typical shape memory properties may disappear. The solid state welding process, such as friction stir welding, is thus attractive for SMA joining and it exhibits potentials for achieving welded joints affected by microstructural changes that preserve the shape memory properties. The present study investigates the feasibility of friction stir welding process to join NiTi shape memory alloys; in order to analyse the welding process, it…

Dissimilar titanium/aluminum friction stir welding lap joints by experiments and numerical simulation

Dissimilar lap joints were produced by friction stir welding (FSW) out of Ti6Al4V titanium alloy and AA2024 aluminum alloy sheets. The joints, welded with varying tool rotation and feed rate, were studied by analyzing the maximum shear strength, Vickers microhardness and optical observations. A dedicated numerical model, able to take into account the presence of the two different alloys, was used to highlight the effects of the process parameters on temperature distribution, strain distribution, and material flow. The combined analysis of experimental measurements and numerical predictions allowed explaining the effects of tool rotation and feed rate on the material flow. It was found that …

Mechanical and microstructural characterization of titanium gr.5 parts produced by different manufacturing routes

Abstract In recent years, the aircraft industry has shifted its preference for metal parts to titanium and its alloys, such as the high-strength Titanium Grade5 alloy. Because of Titanium Grade 5 limited formability at ambient temperature, forming operations on this material require high temperatures. In these conditions, a peculiar microstructure evolves as a result of the heating and deformation cycles, which has a significant impact on formability and product quality. On the other hand, additive manufacturing technologies, as selective laser melting and electron beam melting, are increasingly being used and are replacing more traditional approaches such as machining and forging. Fundamen…

Effect of process parameters on the joint integrity in Friction Stir Welding of Ti-6Al-4V lap joints

Finite Element Studies On Friction Stir Welding Processes of Tailored Blanks

Although friction stir welding (FSW) has been successfully used to join materials that are difficult-to-weld or unweldable by fusion welding methods, it is still in its early development stage and, therefore, its potential has not been fully exploited yet. FSW appears to be a very promising process for tailor-welded blanks to overcome the difficulties encountered in traditional fusion welding processes for obtaining a sound welding with good nugget integrity. In this paper the friction stir welding process for tailored blanks of aluminum alloy is investigated through a FEM developed by the authors. In particular FSW for sheets with different thicknesses is studied. For each setup a differen…

ELECTROCHEMICAL ANALYSIS ON FRICTION STIR WELDED AND LASER WELDED 6XXX ALUMINIUM ALLOYS T-JOINTS

Friction Stir Welding (FSW) and Laser Welding (LW) can be successfully employed to weld aluminium alloys, in many cases overcoming the difficulties encountered with more conventional welding processes like MIG or TIG. The corrosion resistance of the welded joint remains, however, an important issue, especially in applications (like in aircrafts), where corrosion can induce structural failure: the weld region has often lower mechanical resistance in comparison with the parent material and a decrease in its corrosion resistance, especially when the corrosion damage can represent a potential crack initiation site, can be unacceptable in components design. In this work the corrosion resistance …

Friction stir welding of lap joints: Influence of process parameters on the metallurgical and mechanical properties

Abstract Aluminum alloys are widely used in the aircraft industries even if such materials present lower ductility with respect to steels, anisotropy phenomena and, more important, they are often “difficult” to be welded or even “non-weldable”. In the last years the friction stir welding process (FSW) was proposed and applied in order to get good mechanical and technological performances of the joints. In this paper, an experimental and numerical investigation on the lap joining of AA2198-T4 aluminum alloy blanks by FSW is presented. In particular the joints strength and metallurgical properties are investigated by varying the joint configuration and the tool geometry and rotational speed. …

Comparison between FSW and bonded lap joints - A preliminary investigation

Difficult to weld aluminium alloys can be effectively joined by different alternative processes. Friction Stir Welding (FSW), among the solid-state processes and adhesive bonding represent two very attractive techniques. They allow the production of highly resistant joints avoiding the formation of the typical fusion weld defects. The aim of this work is to identify, analyse and compare the mechanical properties of AA6016 aluminium alloy joints made out of 1 mm thick sheets. FSW lap joints were and epoxy bonded joints were produced. Using the FSW results as benchmark, the overlap required in the bonded joint was identified to ensure the same static strength. Once the geometric configuration…

Advances and innovations in manufacturing systems research 2022

Tool Path Design in Friction Stir Spot Welding of AA6082-T6 Aluminum Alloys

In the paper, a variation of the Friction Stir Spot Welding (FSSW) process has been considered. In particular, a particular tool path is given after the sinking phase nearby the initial penetration site. The process mechanics was highlighted and the joint strength was considered at the varying of the most relevant process parameters. Furthermore macro and micro analyses were developed in order to highlight the process mechanics and the local material microstructure evolution. The investigated technology appears a promising joining technique in order to develop effective spot joints.

Residual stresses in friction stir welded parts of complex geometry

Residual stresses play a key role on the mechanics underlying the fatigue crack growth propagation of welded joints. Indeed, compressive residual stresses may induce a beneficial enhancement of the fatigue life under loading condition whereas tensile residual stresses may act to increase the stress distribution at crack tip, resulting in a life-threatening condition of the welded structure. In-process distortion and final geometry of welded joints are also affected by residual stresses. In this paper, the longitudinal residual stress distributions in friction stir welding (FSW) joints were investigated for butt and skin–stringer geometries, including lap and T configurations. To measure res…

Numerical simulation of modified friction stir spot welding processes

Experimental and numerical analysis on FSWed magnesium alloy thin sheets obtained using “pin” and “pinless” tool

Comportamento a Fatica di Giunti Ibridi (Spr/Incollati) Cfrp-Alluminio

Analysis of Material Formability in Incremental Forming

Abstract Incremental forming is an innovative sheet metal forming technology in which a blank is plastically deformed through the progressive action of a small-size punch, whose movement is governed by a CNC machine. In this way the tool locally deforms the material through an almost pure stretching deformation mechanics. The paper is focused on material formability in incremental forming. Several tests were developed, aimed to the achievement of different straining conditions in the material and consequently to the determination of Forming Limit Diagrams for progressive forming operations. The features and the application of such FLD are discussed in the paper.

Residual Stress Effects on Fatigue Crack Growth in Ti-6-4 Friction Stir Welds

A Neural Network Based Approach for the Design of FSW Processes

Friction Stir Welding (FSW) is an energy efficient and environmentally "friendly" welding process. The parts are welded together in a solid-state joining process at a temperature below the melting point of the workpiece material under a combination of extruding and forging. This technology has been successfully used to join materials that are difficult-to-weld or ‘unweldable’ by fusion welding methods. In the paper a neural network was set up and trained in order to predict the final grain size in the transverse section of a FSW butt joint of aluminum alloys. What is more, due to the relationship between the extension of the “material zones” and the joint resistance, the AI tool was able to…

Local Mechanical and Morphological Characterization of Friction Stir-Welded Butt Joints

In this paper the results of an experimental investigation into the local mechanical and morphological characterization of AA6082-T6 friction stir-welded (FSW) butt joints are illustrated. The softening effects of the welding process are highlighted through the use of micro-indentation tests on the top surface of the specimens. The effect of post-welding heat treatments was investigated, also.

An Automated Visual Inspection System for the Classification of the Phases of Ti-6Al-4V Titanium Alloy

Metallography is the science of studying the physical properties of metal microstructures, by means of microscopes. While traditional approaches involve the direct observation of the acquired images by human experts, Com-puter Vision techniques may help experts in the analysis of the inspected mate-rials. In this paper we present an automated system to classify the phases of a Titanium alloy, Ti-6Al-4V. Our system has been tested to analyze the final products of a Friction Stir Welding process, to study the states of the micro-structures of the welded material.

Friction stir welding FEM model improvement through inverse thermal characterization

Experimental and numerical study on Linear Friction Welding of AA2011 Aluminum Alloy

Solid State Joining of Thin Hybrid Sandwiches Made of Steel and Polymer: a Feasibility Study

Abstract The growing demand for more environmentally friendly vehicles has led to an increased use of light materials in the transportation industry with the aim to reduce structural weight, fuel consumption, and gas emissions, thereby boosting cost-effectiveness and recyclable properties. Complex multi-material steel-based components would allow to improve mechanical properties and minimize weight even further. In particular, new sandwich materials made by steel outer skins and a polymeric internal layer seems very promising for obtaining mechanical performance and lightness at the same time. Unfortunately, traditional welding techniques, like arc welding, laser welding, and resistance spo…

New Materials Design Through Friction Stir Processing Techniques

Friction Stir Welding (FSW) has reached a large interest in the scientific community and in the last years also in the industrial environment, due to the advantages of such solid state welding process with respect 1(o) the classic ones. The complex material flow occurring during the process plays a fundamental role in such solid state welding process, since it determines dramatic changes in the material microstructure of the so called weld nugget, which affects the effectiveness of the joints. What is more, Friction Stir Processing (FSP) is mainly being considered for producing high-strain-rate-superplastic (HSRS) microstructure in commercial aluminum alloys. The aim of the present research…

Investigations on the linear friction welding process through numerical simulations and experiments

Abstract Linear Friction Welding (LFW) is a solid-state joining process applied to non-axisymmetric components. LFW involves joining of materials through the relative motion of two components undergoing an axial force. In such process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and eventually bonding conditions. In the paper the authors present a designed and assembled laboratory fixture for LFW operations and the results of an experimental and numerical campaign aimed to weld steel parts. The dedicated fixture permitted to highlight the effect of the most important process parameters. Process conditions allowing ef…

Process parameters and surface treatment effects on the mechanical and corrosion resistance properties of Ti6Al4V components produced by laser powder bed fusion

Laser powder bed fusion is one of the additive manufacturing technologies which has developed more rapidly in recent years as it enables the production of very complex geometries. Titanium alloys are among the most popular materials in the aerospace industry thanks to excellent mechanical and corrosion resistance. The corrosion behavior and mechanical properties of samples made of Ti6Al4V and characterized by the geometrical features typical of brackets were investigated taking into account the effects of process parameters on porosity and microstructure. A comparison between the corrosion resistance of samples with complex geometry (3D) and specimens characterized by simple geometry (FLAT)…

Improving formability in SPIF processes through high speed rotating tool: experimental and numerical analysis

Single-point incremental forming (SPIF) is a quite new sheet-forming process which offers the possibility to deform complex parts without dedicated dies using a single-point tool and a standard three-axis CNC machine. Although the process mechanics enables higher strains with respect to traditional sheet-forming processes, research has been focused on further increasing the maximum forming angle. In the paper, a new approach is used to enhance the material formability through a localized sheet heating as a consequence of the friction work caused by high speed rotating tool. Numerical simulation was utilized to relate the effect of temperature with the main field variables distribution in th…

Microstructural Changes Determining Joint Strength in Friction Stir Welding of Aluminium Alloys

In the paper the results of a wide experimental activity on friction stir welding (FSW) of aluminum alloys are reported. In particular the butt joints of two different materials, namely AA1050-O and AA6082-T6 were considered. Grains dimensions and precipitates density were investigated both in the parent materials and after the welding processes. Furthermore post-welding heat treatments effects on the joint strength were studied.

On the Field Variables Influence on Bonding Phenomena during FSW Processes: Experimental and Numerical Study

Solid state bonding recurs in several manufacturing processes, as Friction Stir Welding (FSW), Linear Friction Welding (LFW), extrusion of hollow profiles and Accumulative Roll Bonding (ARB). The former processes are nowadays of particular industrial interest because of the specific advantages with respect to the classic welding technologies. In FSW the solid state bonding is obtained between an undeformed cold material, already placed in the advancing side of the joint, and the hot material flow incoming from the retreating side. Proper conditions of pressure, temperature, strain and strain rate are needed in order to get the final effective bonding. In the paper experimental tests on butt…

Shear coefficient determination in linear friction welding of aluminum alloys

In the present study, a combined experimental and numerical investigation on Linear Friction Welding (LFW) of AA2011-T3 aluminum alloy was carried out in order to find the temperature dependent shear coefficient to be used in a 3D numerical model of the process. Torque, oscillation frequency and pressure were acquired in order to calculate the shear stress at the interface. A numerical thermal model was used to calculate the temperature at the interface between the specimens starting from experimental temperatures acquired through a thermocouple embedded in the LFW specimens. Finally, the calculated shear coefficient was used to model the contact between the two specimens in a dedicated 3D,…

In-process control strategies for friction stir welding of AZ31 sheets with non-uniform thickness

Two different in-process control strategies were developed and compared with the aim to produce AZ31 magnesium alloy joints by friction stir welding on sheet blanks with a non-uniform thickness. To this purpose, sheets with dip or hump zones were welded by either changing the rotational speed or the tool plunging in order to keep constant the value of the vertical force occurring during the welding stage of the process. The influence of the main process parameters on the tool force, the micro- and macromechanical properties, and the joints microstructures in the dip and hump zones were analyzed. The results showed that using the rotational speed change-based approach, the hump zones are sub…

Experimental and Numerical Analysis of Microstructure Evolution during Linear Friction Welding of Ti6Al4V

Abstract Linear Friction Welding (LFW) is a solid state welding process used to joint bulk components. In the paper, an experimental and numerical study on LFW of Ti6Al4V titanium alloy is presented. A laboratory designed LFW machine has been used to weld the specimens with different contact pressure and oscillation frequency. The joint microstructure has been experimentally observed with SEM and EDS. A dedicated numerical model, able to predict temperature, strain and strain rate distribution as well as the phase volume fraction evolution, has been utilized to predict the final microstructure in the welded parts. It was found that complete transformation of the alpha phase into beta phase …

On the Finite Element Simulation of Secondary Operations on Metallic Foams

Metallic foams have been recently introduced also as industrial materials due to their well known advantages. In fact, their low mass in conjunction with the good thermal and mechanical properties push toward an extensive diffusion in manufacturing industry. In the study here addressed, a very accurate investigation concerning the latter two aspects has been carried out. In fact, a secondary manufacturing process, i.e. the foam bending, has been taken into account. Anyway, all the knowledge derived for sheet metal bending is not directly applicable to the foams. A finite element code has been utilized for modeling the foam behavior during the bending processes and an accurate material rheol…

An energy efficiency analysis of Single Point Incremental Forming as an Approach for Sheet Metal Based Component Reuse

Abstract Producing materials causes about 25% of all anthropogenic CO2 emissions. Metals play a significant role, steel and aluminum account for 24% and 3% of worldwide material related emissions respectively. Fostering resources efficiency strategies in the field of sheet components could lead to a significant environmental impact reduction. Reshaping could be one of the most efficient strategy to foster material reuse and lower the environmental impact due to material production. Specifically, for aluminum recycling, the overall energy efficiency of conventional route is very low and, more importantly, permanent material losses occur during re-melting because of oxidation. The present pap…

Technological Alternatives in the Joining of Lightweight Alluminum Structures

A numerical approach for the modelling of forming limits in hot incremental forming of AZ31 magnesium alloy

AbstractMagnesium alloys, because of their good specific material strength, can be considered attractive by different industry fields, as the aerospace and the automotive one. However, their use is limited by the poor formability at room temperature. In this research, a numerical approach is proposed in order to determine an analytical expression of material formability in hot incremental forming processes. The numerical model was developed using the commercial software ABAQUS/Explicit. The Johnson-Cook material model was used, and the model was validated through experimental measurements carried out using the ARAMIS system. Different geometries were considered with temperature varying in a…

Measuring of Geometrical Precision of Some parts Obtained by Asymmetric Incremental Forming Process After Trimming

Asymmetric Incremental Forming exalts the advantages of Incremental Forming process since no dies are strictly necessary. In this way complex geometries may be manufactured with a very simple clamping equipment. On the other hand, this characteristic determines some intrinsic drawbacks which penalise its industrial suitability; first of all, the dimensional control of the manufactured part is a still open point for researchers all over the world. Several approaches have been already proposed in the last years to solve the problem, resulting only in partial solutions. At the same time, up to now, the numerical simulation did not supply significant aid to the designers, due to the problem com…

A novel linear friction welding based approach for sheet-bulk joining

In the last decades, the development of new, flexible manufacturing processes caused the increase of the demands for highly customized complex functional parts in many industrial fields. The peculiar design of these components often overcome conventional sheet metal and bulk metal forming processes capabilities. In order to face this issue, new hybrid techniques, capable of exploit key advantages of different processes, have to be developed. In this paper, a novel approach based on the Linear Friction Welding process is proposed to obtain sheet-bulk joints. The feasibility of the technique on high specific strength alloys is investigated through an experimental campaign.In the last decades,…

Friction Stir Welding of Magnesium Alloys under Different Process Parameters

Experimental and numerical investigations have been performed in order to study the effect of welding parameters on properties of FSW-ed AZ31 magnesium alloy sheets. The results, presented in terms of tensile strength and numerical field variables distributions, allow to understand the behaviour of such material when FSW-ed using different rotational and welding speeds for a given tool geometry.

Geometrical deviation of end-of-life parts as a consequence of reshaping by single point incremental forming

AbstractPutting in place circular economy strategies is an urgent challenge to face. In this scenario, manufacturing processes play a relevant role as efficient material reuse enabler. Scientists have to make an effort either to find new process or to rethink old process to reprocess end-of-life (EoL) component to recover both material and functions. In this paper, single point incremental forming (SPIF) process is used for reshaping sheet metal EoL components. The entire process chain was replicated including both deep drawing process (to imitate the end-of-life component) as well as SPIF operations (to obtain the reshaped components). The geometrical deviation as a consequence of SPIF ope…

Friction stir welding of tailored joints for industrial applications

Friction stir welding (FSW) is an energy efficient and environmentally "friendly" (no fumes, noise, or sparks) welding process, during which the workpieces are welded together in a solid-state joining process at a temperature below the melting point of the workpiece material under a combination of extruding and forging. Since its invention in 1991 by TWI, such process has been reaching a continuously increasing popularity among aerospace, automotive and shipbuilding industries due its capability to weld unweldable or difficult-to-weld light alloys in different joint morphologies. In this paper a wide experimental campaign is carried out in order to obtain T and lap joints characterized by d…

Fatigue resistance of AA2024-T4 friction stir welding joints: Influence of process parameters

On the linear friction welding process of aluminum alloys: Experimental insights through process monitoring

Abstract Linear friction welding is a solid-state joining process for non-axisymmetric components in which joining of materials is obtained through the relative motion of two components under pressure. In the process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and eventually bonding conditions. A dedicated fixture was equipped with sensors for the in-process acquisition of variables regarding kinematics, dynamics and temperature levels. The results of an experimental campaign aimed to weld AA6082-T6 aluminum alloy parts are presented and a process window is identified for the used alloy.

Dual phase titanium alloy hot forging process design: experiments and numerical modeling

Titanium alloys are considered desirable materials when both good mechanical properties and weight reduction are required at the same time. This class of materials is widely used in those fields (aeronautics, aerospace) in which common steels and light-weight materials, e.g., aluminum alloys, are not able to satisfy all operative service conditions. During the last decade, forging of titanium alloys has attracted greater attention from both industrial and scientific/academic researchers because of their potential in providing a near net shaped part with minimal need for machining. In this paper, a numerical model of the forging sequences for a Ti-6Al-4V titanium alloy aerospace component is…

Dissimilar material lap joints by Friction Stir Welding of Steel and Titanium Sheets: Process Modeling

In the paper a continuum based FEM model for Friction Stir Welding of different material lap joint made out of thin stainless steel and titanium sheets is proposed. The simulation campaign was made out using the 3D Lagrangian implicit code DEFORM{trade mark, serif} by means of a rigid-visco-plastic approach. The model, already set up and tuned for FSW process of similar materials and geometrical configurations takes into account the different mechanical and thermal behavior of the two materials and the microstructural evolution of the considered titanium alloy in the same joint. Additionally, it is able to predict temperature, phase, strain and strain rate distributions and evolution at the…

Pin shape effect on friction stir welding af AA6082-T6 sheets

Friction stir assembly of alluminium alloy

Design of Numerical Simulations of Linear Friction Welding Processes: Issues and Difficulties

In this paper, a critical analysis of the technical difficulties and numerical issues in running simulations of linear friction welding processes is carried out. The focus of the paper is the comparison of different modeling strategies of a numerical analysis for the LFW process of Ti-6Al- 4V titanium alloy, for which the thermal aspect strongly influences the mechanical behavior due to the phase transformation, taking place over a definite range of temperature. A 3D simulation campaign, conducted using the FEA code DEFORM™, was considered in order to show advantages and disadvantages of each approach, including the most critic limitations and complexity in a correct simulation design using…

Using a neural network for qualitative and quantitative predictions of weld integrity in solid bonding dominated processes

Solid-state bonding occurs in several manufacturing processes, as Friction Stir Welding, Porthole Die Extrusion and Roll Bonding. Proper conditions of pressure, temperature, strain and strain rate are needed in order to get effective bonding in the final component. In the paper, a neural network is set up, trained and used to predict the bonding occurrence starting from the results of specific numerical models developed for each process. The Plata-Piwnik criterion was used in order to define a quantitative parameter taking into account the effectiveness of the bonding. Excellent predictive capability of the network is obtained for each process.

Influence of geometrical ratios in forgeability of complex shapes during hot forging of Ti-6Al-4V titanium alloy

Abstract Titanium alloys are considered desirable materials when both mechanical properties and weight reduction are requested at the same time. This class of materials is widely used in application fields, like aeronautical, in which common steels and light-weight materials, like aluminum alloys, are not able to satisfy all operative service conditions. Most of manufacturing processes of titanium alloy components are based on machining operations, which allow obtaining very accurate final shapes but, at the same time, are affected by several disadvantage like material waste and general production costs. During the last decade, the forging processes for titanium alloys have attracted greate…

On the use of resin tools in sheet metal stamping of small lots

Material flow and CDRX phenomena determining joint resistance in AA7075-T6 friction stir welding

Aluminium sheet metal scrap recycling through friction consolidation

Abstract In the last decades, several direct-recycling techniques have been developed and investigated in order to avoid material remelting, typical of the conventional aluminum alloys recycling processes. Moreover, the remelting step for aluminum recycling is affected by permanent material losses. Solid-state recycling processes have proven to be a suitable strategy to face such issues. Friction Consolidation is an innovative solid state-recycling technology developed for metal chips. During the process, a rotating die is plunged into a hollow chamber containing the material to be processed. The work of friction forces decaying into heat soften the material and, together with the stirring …

Latest advancements in manufacturing systems at NAMRC 45

Latest manufacturing technologies are more prevalent thanbefore due to recent industrial revolution (or Industry 4.0), continu-ous business decentralization and needs for better overall resourceefficiency and effectiveness. Manufacturers are competing in aglobal, dynamic marketplace that demands excellence in qual-ity and service, throughput, innovativeness, agility in production,short response time to changing markets, and tight profitable mar-gins. In the 21 st century, manufacturing will be gradually pushedtowards a distributed environment with increasing dynamism oruncertainty. It is envisioned that Cyber-Physical Systems (CPS),Cloud Manufacturing, Internet of Things, and Big Data Analy…

Enhancement of mechanical properties of FSWed AA7075 lap joints through in-situ fabrication of MMC

Abstract Friction Stir Processing (FSP) has been demonstrated feasible to create local Metal Matrix Composites (MMCs) in light alloys matrix. In this research, local MMCs were produced contextually to the weld using Friction Stir Welding (FSW). SiC particles were added to AA7075 lap joints by creating a proper groove on the top surface of the bottom sheet. Different welds were produced with increasing number of tool passes. The effect of the multiple passes was investigated through shear tests, macro and micro observations, average grain size and microhardness measurements. The welded joints were compared to a reference weld produced with no reinforcements. It was found that poor mixing bet…

On the self-piercing riveting of aluminium blanks and carbon fibre composite panels

In the present paper the possibility to join aluminium alloys blanks and carbon fibre composites panels by self-piercing riveting operation is considered. In particular a few case studies were carried out at the varying of the process parameters. The effectiveness of the obtained joints was tested through tensile tests and through fatigue ones; what is more the process mechanics was highlighted through proper macro and micro observations of the transverse sections of the joints. The failure mechanics of the obtained joints were also considered in order to highlight the mechanisms which occur and determine the lost of the load carrying capability of the joints. Finally a numerical model of t…

Numerical modelling of friction stir welding: a grain size evolution model

Utensile di saldatura per attrito

Influence of Joint Geometry on Micro and Macro Mechanical Properties of Friction Stir Spot Welded Joints

AbstractSpot welding can be considered a very common joining technique in automotive and transportation industries as it permits to obtain effective lap-joints with short process times and what is more it is easily developed through robots and automated systems. Recently, Friction Stir Spot Welding (FSSW) has been proposed as a natural evolution of the already known Friction Stir Welding (FSW) process, allowing to obtain sound spot joints that do not suffer from the insurgence of typical welding defects due to the melting of the base material. Similarly to FSW, both geometrical and technological parameters must be considered as they affect the material flow and the heat flux generated durin…

Friction Stir Welding of 3D Industrial Parts

Fatigue behavior of self-piercing riveting of aluminium blanks and carbon fiber composite panels

The Effect of Building Direction on Microstructure and Microhardness during Selective Laser Melting of Ti6Al4V Titanium Alloy

AbstractDuring the last few years, additive manufacturing has been more and more extensively used in several industries, especially in the aerospace and medical device fields, to produce Ti6Al4V titanium alloy parts. During the Selective Laser Melting (SLM) process, the heterogeneity of finished product is strictly connected to the scan strategies and the building direction. An optimal managing of the latter parameters allows to better control and defines the final mechanical and metallurgical properties of parts. Acting on the building direction it is also possible to optimize the critical support structure. In particular, more support structures are needed for the sample at 0°, while very…

Strategies for numerical simulation of linear friction welding of metals: a review

Linear friction welding (LFW) is a solid-state joining process used to weld non-axisymmetric components. Material joining is obtained through the reciprocating motion of two specimens undergoing an axial force. During this process, the heat source is determined by the frictional work transformed into heat. This results in a local softening of the material and plays a key role in the onset of the bonding conditions. In this paper, a critical analysis of the different approaches used to simulate the LFW processes is provided. The focus of the paper is the comparison of different modeling strategies and the most relevant outputs available, i.e. temperature, strain and stress distribution, mate…

Analisi numerico-sperimentale per la determinazione delle tensioni residue in un giunto saldato

La durata di un componente dipende dall’interazione tra le caratteristiche meccaniche del materiale con cui è costruito e gli sforzi a cui esso è sottoposto. Per la determinazione dello stato tensionale agente, oltre agli sforzi dovuti ai carichi imposti durante l’esercizio, è necessario conoscere accuratamente gli stati tensionali residui derivanti dal processo di produzione. Generalmente, le tensioni residue sono indesiderate poiché possono essere di entità elevata e tale da ridurre la resistenza complessiva del componente meccanico. Un aspetto particolarmente insidioso delle tensioni residue è che la loro presenza viene generalmente riconosciuta solo dopo il verificarsi di un malfunziona…

Improved FE model for simulation of friction stir welding of different materials

Abstract One of the most relevant aspects of friction stir welding is the possibility to weld different materials. In the present paper, the authors present an improved continuum finite element model for the simulation of friction stir welding processes aimed to obtain T joints, made of a stringer in AA7175-T73511 and of a skin in AA2024-T4. The model, taking into account the thermomechanical behaviours of the two different materials, is utilised to study the occurring material flow and residual stress state. Numerical results are compared with experimental observations: the model is able to predict the material flow, obtaining important information on the joint failure mode.

Design of continuous Friction Stir Extrusion machines for metal chip recycling: issues and difficulties

Abstract Friction Stir Extrusion is an innovative direct-recycling technology developed for metal machining chips. During the process, a rotating die is plunged into a cylindrical chamber containing the material to be recycled. The stirring action of the die prompts solid bonding phenomena allowing the back extrusion of a full dense rod. One of the main weakness of this technology is the discontinuity of the process itself that limits the extrudates volume to the capacity of the chamber. In order to overcome that limitation, a dedicated extrusion fixture has to be developed, keeping into account the concurrent needs of a continuous machine. The geometry of the die has to ensure proper press…

On microstructural phenomena occurring in friction stir welding of aluminium alloys

Abstract The results of experimental activity on friction stir welding (FSW) of aluminum alloys are reported. Butt joints of two different materials, namely AA2024-T4 and AA7075-T6, were investigated from a metallurgical point of view. Grain dimensions and insoluble particle densities were investigated both in the parent materials and in the joints. Furthermore, the effect of post-welding heat treatments on the joint strength was studied.

Innovative user defined density profile approach to fsw of aluminium foam

Metallic foams are one of the most exciting materials in the world of mechanical industry due to their reduced mass and the good mechanical, thermal and acoustic characteristics. Consequently, their application, is increasing day by day even with the important drawbacks that reduce their suitability and diffusion such as high manufacturing cost and difficulty in processing. An innovative approach is outlined in this paper that enables the production of complex shapes taking advantage of deformation processing and friction stir welding (FSW). The aim is to create customized tailored manufactured parts. The cellular construction of foams makes this approach rather challenging as the cell wall…

Ingegnerizzazione di giunti SPR a semplice sovrapposizione CFRP-Al

Special Issue of Journal of Manufacturing Systems on Advancing Manufacturing Systems Research at NAMRC 46

Special Issue of Journal of Manufacturing Systems on Advancing Manufacturing Systems Research at NAMRC 46

Beta forging of Ti-6Al-4V: Microstructure evolution and mechanical properties

Titanium alloys are finding an increasing use in the aeronautical field, due to their characteristics of high mechanical properties, lightness and corrosion resistance. Moreover these alloys are compatible with the carbon fibre reinforced plastics that are also finding a wide use in the aeronautical field. On the other hand the use of these alloys implies some drawbacks, for example titanium alloys are often considered more difficult to form and generally have less predictable forming characteristics than other metallic alloys such as steel and aluminum. In this paper was studied both the microstructure evolution and the mechanical properties of a Ti-6Al-4V rolled bar after hot forging. The…

Friction stir extrusion to recycle aluminum alloys scraps: Energy efficiency characterization

Abstract Solid state recycling refers to a group of processes allowing direct recycling of metals scraps into semi-finished product. Their main advantage lies in avoiding the molten state of the material which badly affects the environmental performance of the conventional (remelting based) recycling routes. It is expected that such process category would lower the environmental performance of metals recycling. In this paper, the friction stir extrusion process for aluminum alloy AA 2050 wire production is analyzed under the primary energy demand perspective. The process electrical energy demand is quantified with varying process parameters. An empirical modelling approach was applied and a…

Influence of some relevant process parameters on the dimensional accuracy in incremental forming: a numerical and experimental investigation

Abstract As known, incremental forming is a flexible and innovative sheet metal forming process which allows complex shape shells forming without the need for any die. For these reasons, incremental forming is nowadays suggested for rapid prototyping and customised products. The present paper is focused on material formability in incremental forming and, in particular, on the evaluation and compensation of elastic springback. The latter significantly modifies the imposed shape. For this purpose, a deeper assessment of the process was developed following three different approaches. First of all, a wide experimental investigation on the influence of some relevant process parameters was develo…

Numerical modelling of the linear friction welding process

Linear friction welding (LFW) is a solid-state joining process applied to non-axisymmetric components. LFW involves joining of materials through the relative reciprocating motion of two components under an axial force. In such process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and proper bonding conditions due to both the temperature increase and the local pressure of the two edges to be welded. In the present work the authors present a numerical model of the linear friction welding process of AISI 1045 parts. The numerical model allowed to highlight the process mechanics and the physical conditions which must be r…

Tool Geometry in Friction Stir Welding of Magnesium Alloy Sheets

Comparative evaluation of the effect of the substrate thickness and inherent process defects on the static and fatigue performance of FSW and adhesive-bonded overlap-joints in an AA6016 alloy

Abstract This work aims at evaluating the mechanical performance of joints in an AA6016 alloy, manufactured by means of two alternative processes: friction stir welding and adhesive bonding. Given its wide use in industrial fields such as automotive and aeronautics, an overlap configuration of joints was selected for the study, and a specific method based on the overlap length evaluation has been developed to allow comparisons among the cases. Two substrate thicknesses are considered in order to vary the overall joint stiffness, and the effect of such geometrical parameter on the mechanical behavior of the joined system is experimentally investigated. The experimental findings highlight tha…

Resistenza a fatica di giunzioni saldate per attrito: influenza dei parametri di processo

Micro and macro mechanical characterization of friction stir welded Ti–6Al–4V lap joints through experiments and numerical simulation

Abstract Lap joints of Ti–6Al–4V were produced and the effect of the main process parameters was studied through macro and micro investigations highlighting mechanical resistance, microhardness profiles, grain size and phase distributions. A dedicated numerical model was used to link the input process parameters to temperature and strain distributions and to the final microstructure in the welded joint. It is found that the strain produced in the stir zone by proper combination of process parameters plays a fundamental role in the final microstructure and mechanical properties of the joints.

Finite element simulation of friction stir welding

On the use of SPH for Mechanical Engineering structural analyses: an elastic linear case

In-process tool rotational speed variation with constant heat input in friction stir welding of AZ31 sheets with variable thickness

In the present work, friction stir welding experiments on AZ31 magnesium alloy sheets, characterized by a variable thickness along the welding line, were carried out. The approach adapted during welding consisted in maintaining constant the heat input to the joint. To this purpose, the rotational speed of the pin tool was increased with decreasing thickness and decreased with increasing thickness in order to obtain the same temperatures during welding. The amount by which the rotational speed was changed as a function of the sheet thickness was defined on the basis of the results given by FEM simulations of the FSW process. Finally, the effect of the in-process variation of the tool rotatio…

FSW of Lap and T-Joints

Even if in the last years several researches have studied the Friction Stir Welding (FSW) process, it should be observed that most of these studies are concerned with the butt joint and just a few of them extend to more complex geometries. It is worthy to notice that the acquired knowledge on FSW process of butt joints is not immediately extendable to lap and T-joints. The first observation is that in butt joints the surface to be welded is vertical, while in lap and T-joints it is horizontal and placed at the bottom of the top blank to be welded; in this way a major vertical component of the material flow is required to obtain sound joints. In the FSW of lap-joints four different geometric…

Effective Linear Friction Welding Machine Redesign through Process Analysis

Linear friction welding is a solid-state joining process developed for non-axisymmetric components in which the joining of the specimens is obtained through reciprocating motion and pressure. In the process, the friction forces work due to the high frequency oscillation and the pressure between the specimens is converted in thermal energy. In order to design an effective machine, relevant issues derive from the high frequency and the large inertial forces involved in the process. In this study, the authors describe the redesign of a preexisting prototypal machine for LFW processes. A machine redesign is needed when welding high resistant materials, i.e. steels or titanium alloys, with high …

Development of Magnetic Field-Assisted Single-Point Incremental Forming

Single Point Incremental Forming (SPIF) has recently introduced the concept of material formability enhancement through localized deformation. Since material is processed by means of a pin tool attached to spindle, physical interference (especially in vertical direction) limits attainable shapes with the conventional process. The aim of the following work is to increase the variety of achievable geometries with SPIF through in-process magnetic field assistance. An innovative configuration managing SPIF tool movement using magnetic force is proposed. With this in mind, a magnet configuration was designed to generate a vertical load able to plastically deform a 0.5 mm thick AA1100 aluminum sh…

Computer Aided Design of an Effective Fixture for FSW Processes of Titanium Alloys

During the last years welded titanium components have been extensively applied in aeronautical and aerospace industries because of their high specific strength and corrosion resistance properties. Friction Stir Welding (FSW) is a solid state welding process, currently industrially utilized for difficult to be welded or “unweldable” aluminum and magnesium alloys, able to overcome the drawbacks of traditional fusion welding techniques. When titanium alloys are concerned, additional problems arise as the need for very high strength and high temperature resistant tools, gas shield protection and high stiffness machines. Additionally, the process is characterized by an elevated sensitivity to te…

Application of linear friction welding for joining ultrafine grained aluminium

Abstract Ultrafine grained (UFG) materials are of great potential in industry due to their enhanced mechanical strength and other promising features, such as ability to superplastic deformation or excellent corrosion resistance. Nevertheless, one of the main limitations lies in their low thermal stability, which leads to excessive grain growth at elevated temperature. It influences mainly further processes performed at high temperature, such as joining. It causes detrimental problems during conventional fusion welding, as significant grain growth is observed and therefore the advantages as a result of small average grain size disappear. Therefore, the idea of applying solid state joining pr…

A Comparison of Mechanical Properties and Microstructure in Friction Stir Welded and MIG Welded Light Alloys

Joining technologies are in a very interesting phase today due to some relevant innovations concerning new techniques. Friction Stir Welding (FSW) is a relatively new process, patented by TWI in 1991, able to weld through a solid state bonding materials considered difficult to be welded or unweldable by more traditional fusion welding techniques. By using this process welded joints are obtained with no external heat supplier, generating the required temperature increase by means of a revolving pin that follows a proper trajectory partially sunk in the workpiece surface. As for today, although first examples of industrial application can be found in the aeronautical and aerospace fields, the…

Material flow in fsw of aa7075-t6 butt joints: continuous dynamic recrystallization phenomena

In the paper the continuous dynamic recrystallization (CDRX) phenomena occurring in the FSW of AA7075-T6 butt joints is investigated at the varying of the most relevant technological and geometrical parameters. In particular, both experiments and numerical simulations obtained utilizing a 3D Lagrangian implicit, coupled, rigid-viscoplastic model have been developed on FSW butt joints. The resulting microstructure at the core of the weldings is correlated to the material flow occurring during the FSW process.

Metal to composite joining through adhesives

A continuum based fem model for friction stir welding—model development

Although friction stir welding (FSW) has been successfully used to join materials that are difficult-to-weld or unweldeable by fusion welding methods, it is still in its early development stage and, therefore, a scientific knowledge based predictive model is of significant help for thorough understanding of FSW process. In this paper, a continuum based FEM model for friction stir welding process is proposed, that is 3D Lagrangian implicit, coupled, rigid-viscoplastic. This model is calibrated by comparing with experimental results of force and temperature distribution, then is used to investigate the distribution of temperature and strain in heat affect zone and the weld nugget. The model c…

Experimental and numerical investigation on a new FSW based metal to composite joining technique

Abstract In the last decades, different techniques were proposed to join aluminum sheets with composites materials. Each of them has advantages and weak points over the others and new techniques and patents are continuously developed to overcome these difficulties. In this paper an experimental and numerical investigation on a new Friction Stir Welding based approach to mechanically join AA6082-T6 to self-reinforced polypropylene is presented. The aluminum sheet is pre-holed along both the sides of the weld line and a pinless tool generates the heat and pressure needed to prompt back-extrusion of the composite. New experimental fixtures and hole designs were investigated in order to enhance…

Springback Evaluation In Basic Sheet Metal Stamping Processes

In the present paper a measurement technique based on the shadow moire method has been set up in order to evaluate the springback phenomenon in deep drawing operations. Two proper coefficients are introduced to quantitatively describe the effect considered. In particular the proposed technique is able to acquire the final profile of the drawn parts along one or more generatrices, once extracted out from the dies and to compare such profile with the ideal one derived from the dies CAD geometry. The proposed technique has been applied to an axysimmetrical deep drawing operation and moreover the influence of the blankholder force level and of the lubricating conditions have been taken into acc…

Metallurgical Evolutions in Hot Forging of Dual Phase Titanium Alloys: Numerical Simulation and Experiments

Titanium forging has been encountering a growing interest in the scientific and industrial communities because of the distinct advantages it provides with respect to machining, in terms of both mechanical properties of the product and material waste, thus significantly reducing the Buy to Fly ratio. In the paper, a numerical FE model, based on a tri-coupled approach and able to predict the microstructural evolutions of the workpiece during the process, is developed and set up. Calculated results are compared to experiments for a few industrial case studies. The final phases distribution in the forged parts is experimentally measured and compared to the FE model output finding satisfying ove…

Material flow analysis in dissimilar friction stir welding of AA2024 and Ti6Al4V butt joints

The complex material flow occurring during the weld of dissimilar AA2024 to Ti6Al4V butt and lap joints was highlighted through a dedicated numerical model able to take into account the effects of the different materials as well as the phase transformation of the used titanium alloy.

On the Effectiveness of Numerical Prediction of Elastic Springback: An Industrial Case Study

Modelling Aspects in Accumulative Roll Bonding Process by Explicit Finite Element Analysis

Accumulative Roll-Bonding (ARB) process is a severe plastic deformation (SPD) process, capable of developing grains below 1 μm in diameter and improving mechanical properties of the material. In this study, the authors compared two different FE-codes with respect of its applicability for numerical analysis of the ARB process. Modelling this process was achieved using the explicit code for Abaqus/CAE both in 2D and 3D. The proposed model was used to assess the impact of ARB cycles on the final material properties. The numerical results in 2D and 3D were compared and contrasted. The research work presented in this paper is focused on the simulation optimization based on CPU time minimization.…

Friction Stir Welding of steels process design through a continuum based fem model

AbstractFriction stir welding (FSW) has been reaching a continuously increasing popularity among joining processes since its invention in 1991. Although mainly used for aluminium alloys, it has been successfully applied also to steels. In the present paper, a continuum based FEM model for FSW of steels is proposed, which is three-dimensional Lagrangian implicit, coupled, rigid viscoplastic. The model, whose potential has been analysed through temperature distribution comparisons, is able to predict temperature, strain and strain rate distributions, together with thermal and mechanical loads on the welding tool, at varying main process variables. In this way, the FEM model can be used for pr…

Numerical Procedure For Residual Stresses Prediction In Friction Stir Welding

The prediction of residual stresses is a relevant and, under many points of view, still open issue for a proper welding process design. In the present paper a 3D FE model, with general validity for different joint configurations, was used to simulate the Friction Stir Welding (FSW) process of butt joints through a single block approach. The model is able to predict the residual stresses by considering thermal actions only, thanks to a new time efficient approach. A good agreement between calculated and experimentally measured data was found; the effectiveness of the presented numerical procedure was evaluated by comparing the calculation times of the proposed method with the ones of already…

The role of thermal contribution in the design of AA2024 friction stir welded butt and lap joints: mechanical properties and energy demand

Although in recent times the use of solid-state welding processes as friction stir welding (FSW) has become increasingly widespread, for some joint morphologies, as lap joints, there are still signifcantly less data available on both process parameters optimization and energy consumption. In the present paper, the authors investigated the possibility of enhancing the joint quality in two diferent confgurations, i.e. lap and butt joints, taking into account specifc thermal contribution (STC) conferred to the weld. Strength, micro-hardness and microstructure were evaluated on the produced AA2024 aluminum alloys butt and lap joints. The surface response method (RSM) was used to investigate the…

Prediction of Ductile Fractures Occurrence in Deep Drawing of Square Boxes

Abstract The authors propose a new approach for the prediction of tearing in the deep drawing process of square boxes. Such an approach is based on a damage mechanics formulation and in particular on the yield condition for damaging materials proposed by Tvergaard and Needleman and on a strain controlled nucleation model. The flow rule associated to the yield condition is introduced in a finite element explicit formulation founded on the solution of the dynamic equilibrium equation and on an explicit time integration scheme. By this way the developed model allows to calculate the void volume fraction value during the deep drawing process of square boxes and consequently to predict the insur…

Mechanical behaviour and failure modes of metal to composite adhesive joints for nautical applications

In this paper, the influence of several parameters on the mechanical behaviour and failure modes of hybrid bonded joints aluminium/composite was investigated. Particularly, the effects of metallic surface condition, adhesive properties and thickness on single-lap joint resistance were analysed. To these aims, two adhesives were used and, for each adhesive, two different adhesive thicknesses (0.5 and 1.5 mm) have been investigated. Furthermore, two sets of joints for each adhesive kind and thickness were investigated: the former was obtained using aluminium blanks which were previously mechanically treated with sandpaper (P60) and the latter using aluminium treated with sandpaper and with pr…

Numerical simulation of linear fiction welding (LFW) processes

Solid state welding processes are becoming increasingly important due to a large number of advantages related to joining ''unweldable'' materials and in particular light weight alloys. Linear friction welding (LFW) has been used successfully to bond non-axisymmetric components of a range of materials including titanium alloys, steels, aluminum alloys, nickel, copper, and also dissimilar material combinations. The technique is useful in the research of quality of the joints and in reducing costs of components and parts of the aeronautic and automotive industries.LFW involves parts to be welded through the relative reciprocating motion of two components under an axial force. In such process t…

CDRX modelling in Friction Stir Welding of AA7075-T6 aluminum alloy: neural network based approach

Improving Friction Stir Welding of blanks characterized by different thickness

Friction stir welding (FSW) appears to be a promising process even in the welding of blanks of different thicknesses. Actually, such particular tailor welded blanks (TWBs) are usually characterized by a reduction in ductility due to the utilized fusion welding process. In this paper the authors, starting from a preliminary feasibility study, investigate the possibility to improve the mechanical performances of friction stir welded blanks of aluminum alloy with different thicknesses. Both experiments and a FE analyses are developed for a few case studies with different thickness ratios between the blanks. The numerical investigations are performed with the aim to highlight the material tempe…

Friction Stir Welding Lap Joint Resistance Optimization Through Gradient Techniques

In recent years, scientific interest on friction stir welding (FSW) has grown more and more since such a joining technique allows one to weld lightweight alloys that are rather difficult to weld or even “unweldable” with the classic fusion welding operations. Furthermore, few industrial applications of the process are already known in different manufacturing fields. In this paper, the optimization problem of a FSW lap joint for automotive applications is investigated, taking into account process parameters such as the tool rotating speed and the tool feed rate; a numerical gradient technique is applied for the optimization procedure reducing the number of experimental tests to be developed.

Incremental Forming Process for the Accomplishment of Automotive Details

In the last decades the scenario of the industrial production is remarkably changed, since new market requirements have to be faced by the industries. The market, actually, more and more, asks for vary models and niches product. The necessity to intercept dynamically and to satisfy the demands for the market, driver of the innovation process, involves the necessity to reduce the Timeto- market introducing to new methodologies of engineering, like the 3D-prototyping, for the qualitative and structural analysis of the final component. For these reasons, at the beginning of the nineties, a new philosophy of sheet metal forming process begins to assert on the industrial scene, whose basic logic…

On the springback prediction in industrial air bending sequences

Mechanical and metallurgical characterization of AA6082-T6 sheet-bulk joints produced through a linear friction welding based approach

In the last decades, new flexible manufacturing processes have been developed to face the demands, by many industrial fields, for highly customized complex functional parts. The peculiar design of these components often overcomes conventional sheet metal and bulk metal forming processes capabilities. In order to face this issue, new hybrid techniques, capable of exploit key advantages of different processes, have to be developed. In this study, a method to obtain sheet-bulk joints, based on the Linear Friction Welding process, is proposed. The feasibility of the technique was investigated through an experimental campaign carried out with varying pressure and oscillation frequency using AA60…

Experimental Characterization of FSW T-Joints of Light Alloys

Welding is playing a growing role in transport industry due to relevant advantages it allows. Friction Stir Welding is considered one of the most promising joining technologies, especially when it is applied to light alloys. Focusing attention on FSW of T-joints, several parameters have to be considered, and due to thermo-mechanical features of process, T joints need a dedicated approach. A set of previously developed experiments has shown that the tilt angle plays a relevant role in the joint strength. Furthermore it should be observed that T-joints are very often utilized in aerospace industries since the produced structures are composed of joined skins and stingers. Numerous data are rep…

On the use of SLS tools in sheet metal stamping

Abstract A few rapid tooling technologies have been recently proposed and among them Selective Laser Sintering is probably one of the most relevant and promising. In the paper, the authors report some results of a wide experimental research on the application of SLS tools in sheet metal forming. A wear test was earned out to investigate the progressive degradation of laser-sintered materials in comparison with traditional cold-work steels. In particular SLS tools were utilized in a sheet metal stamping process of S-shaped parts: their performances (in terms of tool wear and dimensional quality of the stamped part) were compared with the ones of traditional tools.

Effect of position and force tool control in friction stir welding of dissimilar aluminum-steel lap joints for automotive applications

Widespread use of aluminum alloys for the fabrication of car body parts is conditional to the use of appropriate welding methods, especially if dissimilar welding must be performed with automotive steel grades. Friction stir welding (FSW) is considered to be a reasonable solution to obtain sound aluminum-steel joints. In this context, this work studies the effects of tool position and force control in dissimilar friction stir welding of AA6061 aluminum alloy on DC05 low carbon steel in lap joint configuration, also assessing proper welding parameter settings. Naked eye and scanning electron microscopy (SEM) have been used to detect macroscopic and microscopic defects in joints, as well as t…

Modeling of the Plastic Characteristics of AA6082 for the Friction Stir Welding Process

Focus of this paper is to model the plastic forming behavior of AA6082, in order to develop the numerical FE analysis of the friction stir welding processes and the simulation of subsequent forming processes. During the friction stir welding process, the temperatures reached are until 500 °C and have a fundamental role for the correct performance of the process so the material data has to show a temperature dependency. Because of the tool rotation a strain rate sensitivity of the material has to be respected as well. In this context, the general material characteristics of AA6082 were first identified for different stress states. For the uniaxial state the standard PuD-Al used in the automo…

Properties Augmentation of Cast Hypereutectic Al–Si Alloy Through Friction Stir Processing

AbstractThe present endeavour is to augment mechanical attributes via friction stir processing (FSP) in hypereutectic aluminium–silicon castings by the means of microstructural modifications and defects reduction. Wherein, the study proceeds with mainly two approaches namely, alteration in tool revolution (TR) and the number of FSP passes. The prepared specimens were evaluated investigating volume fraction of porosities, microstructural characterizations and microhardness. Therefrom, the specimen with highest number of passes delivered most uniform properties resulting from the reduction in casting porosities and refined silicon particle uniform distribution throughout friction stir process…

Magnetic field-assisted single-point incremental forming with a magnet ball tool

Abstract This paper describes magnetic field-assisted single-point incremental forming (M-SPIF) with a Nd-Fe-B magnet ball tool. In M-SPIF, the tool driven by magnetic force plastically deforms a sheet. The polarity of the magnet tool helps to make the magnetic force (i.e., forming force) more controllable. In creating a truncated cone, the direction of the magnetic force gradually points more outward as the process progresses, and material is forced outwards from the cone center, increasing thinning in M-SPIF, while the cone center remains undeformed in traditional SPIF. Moreover, M-SPIF creates less localized plastic strain than traditional SPIF while forming the desired geometry.

A Neural Network Based Approach for the Design of FSW Processes

COMPUTATIONAL FLUID DYNAMICS OF TYPE B AORTIC DISSECTION

Type B aortic dissection (AoD) is a disease connected to high blood load on the aortic wall and to a reduced aortic wall resistance. Nowadays, prognosis on type B AoD results to be particularly difficult with an high incidence of patients treated with medical therapy which manifest complication connected with dissection and which should have been treated with surgical repair immediately. This work aims to study those haemodynamical and morphological proprieties of dissected aorta, which can influence the progression or stability of type B AoD. Computational fluid-dynamic analyses were performed on twenty-five patients with type B AoD, whose nine presented an aneurysm evolution and sixteen p…

Friction stir welding: a solid state joining process

A wide experimental investigation on the friction stir welding of AA6082-T6 sheets is presented. In particular the influence of some of the most relevant process parameters was taken into account, with the aim to maximize the joint strength; furthermore the joint fatigue behavior was considered too. An accurate analysis on the obtained parts was carried out, with particular attention to the material microstructure evolution. The obtained results permitted to develop a proper FSW process engineering.

A new approach to study material bonding in extrusion porthole dies

Abstract Porthole die extrusion processes are widely spread even for most recent industrial applications. In turn knowledge base is often linked to make best expertise rather than to scientific fundaments. In the last years several FE models were developed but actual material bonding was not taken into account. In the paper a new approach is presented determining the critical value of the bonding criterion from flat rolling experiments and modelling the actual welding occurring in extrusion of complex profiles. The criterion was tested considering an industrial porthole die extrusion process and experimental parts were analysed to validate the proposed approach.

Thermal Characterization of Friction Stir Welded Butt Joints

PROCESSI DI FORMATURA DI LAMIERE IN ACCIAIO ALTORESISTENZIALE: LA TEMPERATURA COME PARAMETRO DI PROCESSO

Surface and mechanical characterization of stationary shoulder friction stir welded lap joints: experimental and numerical approach

Friction Stir Welding (FSW) is one of the most used solid-state welding processes in the aeronautical, aerospace, ground transportation and naval fields. Stationary Shoulder Friction Stir Welding (SSFSW) is a recently introduced variant of the process allowing lower heat input into the joints, with beneficial effects in terms of joint mechanical properties, microstructure and top surface finish. In the paper, lap joints produced by SSFSW and made out of AA6082-T6 aluminum alloy sheets have been analyzed with the aim to investigate the effect of the stationary shoulder on the lap joints surface, metallurgical, and mechanical properties. The lap joints produced by SSFSW have been compared to …

Sheet Bending Modelling for AA 5083 Aluminium Alloy

An extensive investigation of the V- and U-die bending processes of AA 5083 aluminium alloy has been performed by means of the finite element method and the experimental tests. The predicted results, in terms of elastic springback and loads, were compared with the experimental ones in similar conditions. At a given punch stroke, the springback ratio K increases with the sheet thickness, and, at a constant sheet thickness, K increases with the punch stroke. The comparison between predicted and experimental K values shows an excellent agreement in all the ranges of punch stroke and sheet thickness investigated. A very good agreement between the predicted bending forces and the experimental on…

History of NAMRI and NAMRC

History of NAMRI and NAMRC

Influence of process parameters for thixotropic alloys

With reference to a metallic alloy, the attribute thixotropic is utilized to indicate the behaviour of it in the semi-solid state when its microstructure consists of spheroids in a liquid matrix. Such alloys are characterized by very low values of viscosity under shearing stress in the semi-solid state, while after solidification they show relevant mechanical properties. Actually a structural change from a dendritic structure to a globular one, with the globular grains finely dispersed in a liquid matrix, is observed after particular thermo-mechanical treatments. In the present paper the authors present the results of a wide experimental campaign on the AA 7075 aluminium alloy that shows a …

FEM based prediction of phase transformations during Friction Stir Welding of Ti6Al4V titanium alloy

Abstract Friction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, it is now being successfully used also for high resistant materials. Welding of titanium alloys by traditional fusion welding techniques presents several difficulties due to high material reactivity with oxygen, hydrogen, and nitrogen with consequent embrittlement of the joint. In this way FSW represents a cost effective and high quality solution. The final mechanical properties of the joints are strictly connected to the microstructural evolutions, in terms of phase change, occurring during the process. In the paper a 3D FEM model of the FSW welding proc…

New trends in manufacturing systems research 2021

A New Friction Stir Welding Based Technique for Corner Fillet Joints: Experimental and Numerical Study

Friction stir welding (FSW) is an energy efficient and environmentally "friendly" (no fumes, noise, or sparks) welding process, during which the sheets are welded together in a solid-state joining process. FSW is mature for simple configurations but a significant lack of knowledge is found when dealing with different designs such as T-sections, corner welds and box sections. The present work explores the feasibility of producing corner fillet geometries using FSW. Although such a kind of geometry has traditionally been considered unfeasible for the process, it seems to have a great potential to be used for T-joint configurations, a recurrent design pattern in transport applications. A speci…

Optimal Blankholder Force Path in Sheet Metal Forming Processes: An Al Based Procedure

Abstract Blankholder force plays a fundamental role in the deep drawing process mechanics since it controls, by friction, the material flow into the die cavity. The availability of computer controlled hydraulic presses in the industries promoted a new research field focused on the definition of optimal BHF histories, function of the punch displacement; such studies were aimed to the determination of the so called “process window”, i.e. the BHF path which permits to obtain the maximum height sound component avoiding both wrinkling and tearing. In the paper a design procedure is proposed in order to determine the optimal BHF path in an axisymmetric deep drawing process: in particular, a close…

On the Residual Stresses in Friction Stir-Welded Parts: Effect of the Geometry of the Joints

Residual stress state is a fundamental aspect of welded joints, especially when complex geometries are considered. In this article, the residual longitudinal stresses in friction stir-welded joints were measured. In particular, different joint configurations were taken into account, namely butt joints, T, and lap ones, the latter being definitively interesting case studies with reference to applications in the transportation industries and, particularly in the aerospace industries.

Towards Tool Path Numerical Simulation in Modified Friction Stir Spot Welding Processes

Spot welding can be considered a very common joining technique in automotive and transportation industries as it permits to obtain effective lap-joints with short process times and what is more it is easily developed through robots and automated systems. Recently the Friction Stir Spot Welding (FSSW) process has been proposed as a natural evolution of the already known Friction Stir Welding (FSW) process, allowing to obtain sound spot joints that do not suffer from the insurgence of typical welding defects due to the fusion of the base material. In the paper, a modified Friction Stir Spot Welding (FSSW) process, with a spiral circular movement given to the tool after the sinking stage, is p…

Mode I failure modeling of friction stir welding joints

This paper analyzes mechanical response by finite element method up to the decohesion failure in fracture mode I for joints of friction stir welding (FSW) of an aluminum alloy. It first describes experimental investigations on specimens with FSW embedded, subjected to uniform traction and local punch tests used to characterize local elastic and plastic material parameters. The heterogeneity of the mechanical properties induced by the FSW process is taken into account for the elastic-plastic finite element simulation. The growing damage and the opening failure of the welding zone are described by the adoption of a cohesive interface model with specific mechanical properties.

A novel approach to enhance mechanical properties during recycling of aluminum alloy scrap through friction stir consolidation

Solid state recycling (SSR) is a new approach for making metals recycling more efficient with respect to remelting-based approaches. Friction stir consolidation (FSC) is a new solid-state process that is employed to recycle metallic scraps. Until now, a single-step FSC process was applied to recycled metal chips. During the single-step approach, critical processes parameters, especially processing time and rotational speed, are considered vital to control the quality and mechanical properties of the billet. However, the effectiveness of process parameters is highly restricted by challenging masses of recycling chips and machine competency. The present study first highlights the issues of th…

On the thermo-mechanical loads and the resultant residual stresses in friction stir processing operations

In friction stir welding and processing both a thermal flux and a mechanical action are exerted on the material determining metallurgical evolutions, changes in the mechanical behaviour and a complex residual stress state. In the paper, the metallurgical changes are examined through numerical simulation and experiments to highlight and distinguish the effects of thermal and mechanical loadings. A particular focus is made on the residual stresses generated during the stir processing of AA7075-T6 aluminium blanks. The predictions of FE model are validated by experimental measurements. Lastly, this paper presents an in-process quenching of the processed blanks for improved mechanical propertie…

Mechanical and microstructural characterization of friction stir welded skin and stringer joints

A microstructural and mechanical investigation on lap joints welded by friction stir welding and made out of a 7075-T6 stringer and a 2024-T4 skin is presented. In particular, the metallurgical and mechanical properties of joints have been studied at different tool feed rates (V = 35, 50, 100 mm/min) and constant rotation speed (R = 500 r/min). Temperature distributions have been monitored during the process. It is found that in the welded area, the recrystallized zone (nugget) has an average grain size of about 3 µm and exhibits coarsened MgZn2 particles on grain boundaries. The maximum values of microhardness in the welded skin increase with the process temperature, while they just sligh…

Rilevamento Sperimentale delle Storie di Temperatura in Processi di Friction Stir Welding di Lamiere di Titanio

Innovative sheet metal forming processes: numerical simulations and experimental tests

Abstract In this paper, computer aided engineering of some innovative sheet metal forming processes is reviewed. In particular, tube hydroforming processes and spinning processes are examined. Advanced numerical tools are utilized with the aim to design proper forming operations able to produce sound components. Furthermore, as far as the spinning process is concerned, experimental verifications are carried out to confirm the effectiveness of the numerical predictions.

Ritorno elastico in processi di formatura della lamiera

Solid state bonding mechanics in extrusion and FSW: Experimental tests and numerical analyses

In the paper the authors compare the different solid state bonding mechanics for both the processes of hollow profiles extrusion and Friction Stir Welding (FSW), through the results obtained from a wide experimental campaign on AA6082-T6 aluminum alloys. Microstructure evaluation, tensile tests and micro-hardness measurements realized on specimens extracted by samples of the two processes are discussed also by means of the results obtained from coupled FEM simulation of the processes. ©2007 American Institute of Physics

Modeling of the plastic characteristics of AA6082 for the friction stir welding process

Focus of this paper is to model the plastic forming behavior of AA6082, in order to develop the numerical FE analysis of the friction stir welding processes and the simulation of subsequent forming processes. During the friction stir welding process, the temperatures reached can range up to 500 °C and have a fundamental role for the correct performance of the process, so the material data has to show a temperature dependency. Because of the tool rotation a strain rate sensitivity of the material has to be respected as well. In this context, the general material characteristics of AA6082 were first identified for different stress states. For the uniaxial state the standard PuD-Al used in the…

CDRX modelling in friction stir welding of AA7075-T6 aluminum alloy: analytical approaches

Abstract Friction stir welding (FSW) is an energy efficient and environmentally “friendly” (no fumes, noise, or sparks) welding process, during which the workpiece are welded together in a solid-state joining process at a temperature below the melting point of the workpiece material under a combination of extruding and forging. Significant microstructural evolution takes place during FSW: in particular continuous dynamic recrystallization (CDRX) phenomena result in a highly refined grain structure in the weld nugget and strongly affect the final joint resistance. In the paper two different analytical models aimed to the determination of the average grain size due to continuous dynamic recry…

Prediction of phase transformation of Ti-6Al-4V titanium alloy during hot-forging processes using a numerical model

In this article numerical model for prediction of phase evolution of Ti-6Al-4V titanium alloy was presented. In particular, attention was focused on alpha to beta and beta to alpha+beta phase transformations. The analysis was conducted using a commercial implicit finite element method code, considering the data and the parameters of a real case study to check the quality of the numerical model. The alpha to beta transformation was developed using the simplified form of the Avrami model and the beta to alpha+beta transformation was controlled through the generalized Avrami model. The model so-thought has been used to conduct a 2D simulation of a forging process. A comparison between the num…

Study of the implementation of SPIF as a Reshaping strategy in terms of formability and accuracy performance

The adaption of circular economy strategies has become increasingly necessary in current times. Researches need to be addressed on finding alternative processes or the modification of the existing processes in order to reprocess End-of-Life (EoL) components and consequently recover both materials and their functions. This research paper focuses on the use of single point incremental forming (SPIF) process for the Reshaping of sheet metal EoL components. Uniaxial and biaxial pre-straining was performed on AA5754 sheets to imitate an end-of-life component, and SPIF operations were carried out so as to obtain reshaped components. In previous works, the authors have proven the technical feasibi…

An analysis of through-thickness residual stresses in aluminium FSW butt joints

Abstract In the paper, the results of a wide experimental campaign on friction stir welding (FSW) of aluminum alloys are reported. The attention was focused on the through-thickness residual stresses that occur on aluminum joints, after the welding process. In detail, using the hole-drilling method the residual stresses distribution in the zone close to the tool shoulder border of the joint advancing side, has been investigated; four different aluminum alloys and three different process conditions have been considered. The experimental analysis has shown that unlike traditional welding processes, the residual stresses are negative in the surface of the examined zone, and increase with depth…

Modeling the effect of pin geometry in friction stir welding of aluminum alloys

Design and setup of a Linear Friction Welding fixture

Metallurgical Evolutions in Hot Forging of Dual Phase Titanium Alloys: Numerical Simulation and Experiments

Titanium forging has been encountering a growing interest in the scientific and industrial communities because of the distinct advantages it provides with respect to machining, in terms of both mechanical properties of the product and material waste, thus significantly reducing the Buy to Fly ratio. In the paper, a numerical FE model, based on a tri-coupled approach and able to predict the microstructural evolutions of the workpiece during the process, is developed and set up. Calculated results are compared to experiments for a few industrial case studies. The final phases distribution in the forged parts is experimentally measured and compared to the FE model output finding satisfying ove…

Friction Stir Processing: thermo-mechanical loads and consequent effects on the local material characteristics

The present article is focused on the correlation between the applied thermal and mechanical loads and the consequent effects on the material in friction stir processing (FSP) operations. On one hand, the actions exerted in FSP are split compared to the results obtained with a tool without the pin at its end to a traditional one with a cylindrical pin. In this way, the thermal flux determined by the frictional forces at the tool—shoulder—workpiece interface is secluded from the mechanical stirring action made by the tool pin. On the other hand, the processed specimens are analysed in terms of residual stress state, microhardness, and average grain size values. An in-process heat treatment …

Enhancing formability of aluminium alloys by superimposing hydrostatic pressure

Publisher Summary One of the strategic topics in manufacturing engineering is represented by the reduction of components weight. This aim is pursued by utilizing accurate and effective design tools and using lightweight metals such as aluminum, magnesium, and titanium alloys. Unfortunately, such materials often show a poor ductility, and thus enhancing formability is nowadays one of the most relevant research focus, as well as the development of effective and reliable predictive models of defects insurgence during forming processes. In this scenario, forming by means of superimposed hydrostatic pressure represents a promising alternative manufacturing technique. The chapter discusses the si…

Linear friction welding of dissimilar AA6082 and AA2011 aluminum alloys: microstructural characterization and design guidelines

This paper presents the results of an experimental and numerical campaign on Linear Friction Welding of dissimilar AA2011-T8 and AA6082-T6 aluminum alloys. Experimental tests were carried out with constant oscillation amplitude and process time. Varying oscillation frequency, interface pressure, specimen geometry and mutual position were used. Grain size measurements, HV tests and EDX analysis were considered to characterize the microstructure of the joints as a function of the input process parameters. A thermal numerical model was utilized to predict the temperature profiles in the joints during the process. The obtained results allowed the identification of four weld categories: sound jo…

Advanced numerical models for the thermo-mechanical-metallurgical analysis in hot forging processes

In the paper a literature review of the numerical modeling of thermo-mechanical-metallurgical evolutions of a metal in hot forging operations is presented. In particular models of multiaxial loading tests are considered for carbon steels. The collected examples from literature regard phases transformations, also martensitic transformations, morphologies evolutions and transformation plasticity phenomena. The purpose of the tests is to show the correlation between the mechanical and the metallurgical behavior of a carbon steel during a combination of several types of loads. In particular a few mechanical tests with heat treatment are analyzed. Furthermore, Ti-6Al-4V titanium alloy is conside…

Analysis of Electrical Energy Demands in Friction Stir Welding of Aluminum Alloys

Abstract Manufacturing processes, as used for discrete part manufacturing, are responsible for a substantial part of the environmental impact of products. Despite that, most of metalworking processes are still poorly documented in terms of environmental footprint. To be more specific, the scientific research has well covered conventional machining processes, concerning the other processes there is a lack of knowledge in terms of environmental load characterization instead. The present paper aims to contribute to fill this knowledge gap and an energetic analysis of Friction Stir welding (FSW) is presented. Following the CO2PE! methodological approach, power studies and a preliminary time stu…

Influence of processing parameters and initial temper on Friction Stir Extrusion of 2050 aluminum alloy

Abstract Friction Stir Extrusion is an innovative production technology that enables direct wire production via consolidation and extrusion of metal chips or solid billets. During the process, a rotating die is plunged into a cylindrical chamber containing the material to be extruded. The stirring action of the tool produces plastic flow in the extrusion chamber, densifying and heating the charge so that finally, fully dense rods are extruded. Experiments have been carried out in order to investigate the influence of process parameters and initial temper of the base material on the process variables and on the extrudates’ mechanical properties.

A cost model for the Friction Stir Welding process

FSW of AA6082-T6 T-joints: process engineering and performance measurement

Latest developments in manufacturing processes at NAMRC 45

Manufacturing processes are tightly connected to innovation.They have been the key areas that support and influence a nation’scompetitiveness and economy since the eighteenth century. Asthe primary driving force behind economic growth, manufactur-ing processes enable and facilitate innovative products realization,ranging from heavy-duty machinery to hi-tech home electronics.In the past centuries, they have contributed significantly to moderncivilization and created the momentum that drives today’s econ-omy. Despite various achievements in manufacturing processes, weare still facing challenges due to growing complexity in manufac-turing operations, introduction of new manufacturing technolog…

Developing Tele-Operated Laboratories for Manufacturing Engineering Education

The aim of the PeTEX-project is to establish an e-Learning platform for the development, implementation, and delivery of educational training programs in the field of manufacturing engineering. The PeTEX team designs both: a technical platform for eLearning based on “Moodle” including distributed tele-operated experimentation facilities, and didactic and socio-technical requirements for a successful online learning community. User interfaces are deployed for remote access to instruments, data analysis and multiplexed data access via network protocols. Hence, the platform provides complex tools in order to perform various activities to support the educational process, from telemetric experim…

Process mechanics in Friction Stir Extrusion of magnesium alloys chips through experiments and numerical simulation

Abstract Friction Stir Extrusion (FSE) is a novel process designed to directly recycle machining chips. An experimental campaign was carried out on AZ31 milling chips using variations in extrusion ratio, force and tool rotation rate. The process mechanics were studied and correlated to the material flow, which was elucidated through use of a copper marker. A 3D, Lagrangian, thermo-mechanically coupled dedicated numerical model was set up and validated through temperature measurements. The combination of experimental and numerical results permitted to reconstruct the complex 3D material flow induced by tool rotation and plunge into the extrusion billet chamber.

Comportamento a fatica di giunti a T friction stir wleded in lega di alluminio

On the field variables influence on bonding phenomena during FSW processes: experimental and numerical study

Solid state bonding recurs in several manufacturing processes, as Friction Stir Welding (FSW), Linear Friction Welding (LFW), extrusion of hollow profiles and Accumulative Roll Bonding (ARB). The former processes are nowadays of particular industrial interest because of the specific advantages with respect to the classic welding technologies. In FSW the solid state bonding is obtained between an undeformed “cold” material, already placed in the advancing side of the joint, and the “hot” material flow incoming from the retreating side. Proper conditions of pressure, temperature, strain and strain rate are needed in order to get the final effective bonding. In the paper experimental tests on …

Experimental and Numerical Analysis on FSWed Magnesium Alloy Thin Sheets Obtained Using “Pin” and “Pinless” Tool

The present investigation aims at studying the effect of different tool geometries and process parameters on FSW of thin sheets in AZ31 magnesium alloy. In particular two properly designed tools, with shoulder diameters equal to 8 and 19 mm, were used; each of them was manufactured both in pin and pinless configurations. The effect of the different tool configurations and sizes, and welding parameters on mechanical properties of FSWed joints were analyzed in detail. The results were compared with those obtained on the base material. It was shown that FSWed joints are characterized by strength and ductility values lower than those of base material. Furthermore, the pin tool configuration, wi…

Outlining the Limits of Friction Stir Consolidation as Used as an Aluminum Alloys Recycling Approach

Friction stir consolidation (FSC) is a solid-state process that recycles metal scraps economically and eco-friendly compared to the conventional melting method. The process parameters especially processing time and rotational speed, have a crucial role in achieving a sound disc during FSC. The current study answers the research question of how far these process parameters can be effective when the mass of chips to be recycled increases. In specific, an experimental setup was analyzed that was previously identified as challenging for recycling 20 g chips of aluminum alloy AA 2024-O. Rotational speed was set doubled, and processing time was increased up to 1.5 times of their initial values. T…

Prediction of phase evolutions during friction stir welding of Ti-grade 5 T-joints using finite element modeling

Friction Stir Welding (FSW) is a solid-state welding technology pioneered by The Welding Institute (TWI) in 1991. Originally used to weld aluminum alloys, it is now effectively utilized to weld high-resistance materials as well. The ultimate mechanical characteristics of the joints are inextricably linked to the microstructural evolutions that occur during the process in terms of phase change. It is then crucial, in order to carry out an effective process engineering, to predict the final material microstructure determined by the thermal history that occurred during the process itself. In the paper, a 3D Finite Element Method (FEM) model for the FSW of T-joints is proposed, based on a therm…

A two steps Lagrangian–Eulerian numerical model for the simulation of explosive welding of three dissimilar materials joints

Abstract Explosion welding (EXW) is a solid-state joining process used to produce lap joints out of metal plates of dissimilar materials. During the process, a controlled explosive detonation results in a pressure wave pushing one of the plates to be welded, called flyer, against the other with high velocity. The high pressure and temperature generated, because of the impact energy decaying into heat, create the conditions for solid bonding phenomenon to take place. Due to the complexity of experimental tests, numerical simulation is considered a fundamental design tool for the process. Different approaches are found in literature to simulate the process. In this paper, a dual step Lagrangi…

Key factors for industrial applicability of friction stir welded t-joints of different materials

On the FSW of AA2024-T4 and AA7075-T6 T-joints: an industrial case study

In this paper, the authors present the results of a wide experimental campaign on aeronautical T-shaped parts of industrial interest characterized by dissimilar materials for the skin and stringer. The friction stir welding process engineering was developed with the aim to determine the specific process parameters determining the soundness on the obtained T-parts both from the metallurgical and mechanical point of view. Furthermore, the performance of the obtained T-joints was investigated.

Re-forming end-of-life components through single point incremental forming

Abstract Applying Circular Economy strategies is mandatory to face material demand while minimizing the environmental impact. Manufacturing processes are to be thought as means to enable material/component reuse strategies. This paper presents the suitability of Single Point Incremental Forming (SPIF) to re-form End-of-life sheet metal components. Deep drawing followed by SPIF process on aluminium alloys were carried out to simulate reforming processes chain. The resulting thinning and strain distributions were experimentally analysed for different configurations. The research proves that the local action and enhanced formability nature of SPIF allow non-homogeneously thinned and reduced fo…

A new control parameter to predict micro-warping-induced job failure in LPBF of TI6AL4V titanium alloy

Abstract Laser powder bed fusion (LPBF) includes a few printing techniques widely used, in recent years, concerning the additive manufacturing of Ti6Al4V alloys. These produced parts, typically utilized in sectors such as aerospace and biomedical, are characterized by very high added value. It is therefore fundamental to identify the influence of process parameters typical of LPBF technology on the occurrence of warping leading to process failure. This study deals with the characterization of single-track and “micro-scale” level warping phenomena which may lead to protrusion of material over the powder bed and process failure before normal termination. This phenomenon was investigated as a …

Computer Aided Design of an Effective Fixture for FSW Processes of Titanium Alloys

During the last years welded titanium components have been extensively applied in aeronautical and aerospace industries because of their high specific strength and corrosion resistance properties. Friction Stir Welding (FSW) is a solid state welding process, currently industrially utilized for difficult to be welded or “unweldable” aluminum and magnesium alloys, able to overcome the drawbacks of traditional fusion welding techniques. When titanium alloys are concerned, additional problems arise as the need for very high strength and high temperature resistant tools, gas shield protection and high stiffness machines. Additionally, the process is characterized by an elevated sensitivity to te…

Friction Stir Welding Of AA6082-T6 Sheets: Numerical Analysis And Experimental Tests

3D numerical simulation of the Friction Stir Welding process is developed with the aim to highlight the process mechanics in terms of metal flux and temperature, strain and strain rate distributions. The numerical results have been validated though a set of experimental tests.

Thermal Characterization of Friction Stir Welded Butt Joints

In the paper the thermal characterization of friction stir welding processes (FSW) of aluminium alloys is presented. In particular both embedded thermocouples and a thermography analysis were utilized in order to acquire the temperature vs. time curves in point of interests of the joints and the temperature distributions, respectively. Such kind of results are very important in order to investigate the material conditions during the FSW process.

Mechanical and metallurgical effects of in process cooling during friction stir welding of AA7075-T6 butt joints

This paper presents the results of a combined experimental and numerical investigation focused on the effects of an in process water cooling treatment aimed at improving the final quality of friction stir welded butt joints in terms of mechanical resistance and metallurgy of the processed material. Micro and macro observations, together with the evolution of an already developed finite element tool, have been used to analyze specimens obtained under different process conditions. Water cooling was found to enhance joint strength, reducing the material softening usually observed in the thermo-mechanically affected zone area, with no detrimental effect on nugget integrity.

On the slabbing of stones through diamond wire cutting operations

Diamond wires are usually used in the cutting operations aimed to obtain slabs of stones. This tool consists of a steel cable on which are mounted annular metal—diamond pearls. The use of this technology expanded all over the world because of its advantages on other slabbing techniques as both technical and economical aspects are considered. It should be observed that with this technology wear phenomena must be properly monitored in order to obtain the best process conditions. In this article, the diamond wire cutting operation is investigated, highlighting the process mechanics and the wear phenomena occurring in the used tools. Furthermore, a modified version of the tool itself is propos…

Friction based solid state welding processes

The Relevance Of The Preform Design In Coining Processes Of Cupronickel Alloy

Coining is a forging process in which a metallic disk, characterized by a low volume‐surface ratio, is deformed with the aim to impress 3D images on its three surfaces. Due to the large production volumes and, at the same time, to the high quality standards required to the final products in terms of final dimensions, tolerances and surface finishing, such closed‐die, cold forging process requires a careful evaluation and choice of the proper operative parameters. In particular, along with technological parameters as the die velocity, die stroke and lubrication, which, in turn, contribute to affect the pressure values on the die surfaces, and thus the press choice, geometrical parameters as …

Development of a Design Procedure for Bending Operations

Springback can be considered as one of the most important shape defect in sheet stamping. Such effect results relevant even when simple bending operations are taken into account. In the paper the authors present a design procedure able to provide the proper value of the punch stroke to be applied in order to compensate for elastic springback. In particular two approaches have been followed: firstly an inverse design technique has been utilized in order to find out the response function governing the investigated phenomenon; furthermore neural network techniques have been applied in order to represent the logical link between the input data and the aimed output, i.e. the proper punch stroke …

Friction Stir Welding e Friction Stir Knead Welding per la realizzazione di giunti misti acciaio-alluminio

Effect of the mutual position between weld seam and reinforcement on the residual stress distribution in Friction Stir Welding of AA6082 skin and stringer structures

Abstract In the paper, a numerical and experimental study was carried out to highlight the effect of the distance d between the weld seam and the reinforcement on the residual stress distribution in Friction Stir Welded AA6082-T6 structures. An L-shaped profile was welded to a sheet metal with varying tool rotation and distance d from the weld seam. The Cut Compliance method was used to determine the resulting longitudinal residual stress. A dedicated FE model for FSW was set up, validated and utilized to predict the longitudinal residual stress in the assembled part. The analysis allowed the identification of a few design guidelines in order to reduce the detrimental effects of the residua…

Manufacturing processes as material and energy efficiency strategies enablers: The case of Single Point Incremental Forming to reshape end-of-life metal components

Abstract Making materials consumes about 21% of the global energy demand; concerning metals production, it accounts for about 8% of total global energy consumption. Circular economy strategies such as longer life, more intense use, repair, product upgrades, modularity, remanufacturing, component reuse, and open/closed-loop recycling are strategies to put in place urgently to reduce the environmental impact of raw material production. Although recycling of metals is the most used strategy and is being improved in terms of efficiency, it is mandatory moving towards more virtuous circular economy strategies, such as product/component reuse. In this paper a novel reuse strategy for sheet metal …

Numerical prediction of elastic springback in automotive complex parts

Effetti della temperatura sul ritorno elastico nella piegatura di strisce d’alluminio

An Explicit Model for the Thermal-Mechanical Analysis of Hot Metal Forming Processes

Abstract In the paper the authors propose a new finite element code for the coupled thermal-mechanical analysis of hot metal forming processes. As regards the mechanical problem, an explicit algorithm based on the solution of the dynamic equilibrium equation and an explicit time integration scheme is used, while the heat transfer analysis is based on the solution of the thermal equilibrium equations; in order to put the thermal problem in an explicit linear form a three level scheme has been employed for the discretization of the time variable. The model is based on a staggered procedure, in which the mechanical and the thermal analysis are carried out with respect to different time horizon…

Friction based Solid State Welding Techniques for Transportation Industry Applications

Abstract Solid bonding based processes represent an effective solution in terms of both joints mechanical performances and sustainability. In the last years, both the academic and the industrial researchers focused their work on two solid-state processes: Friction Stir Welding (FSW) and Linear Friction Welding (LFW). The former, patented in 1991 by TWI, is used to weld sheet metal in different joint morphologies, i.e. butt, lap T and 3D joints. The latter has been known for several years, but a growing interest is observed in the last years due to the enhancement of the welding machines performances. LFW, used to join bulk components, is particularly suited for aeronautical and aerospace ap…

Welding abilities of UFG metals

Ultrafine Grained (UFG) metals are characterized by an average grain size of <1 μm and mostly high angle grain boundaries. These materials exhibit exceptional improvements in strength, superplastic behaviour and in some cases enhanced biocompatibility. UFG metals barstock can be fabricated effectively by means of Severe Plastic Deformation (SPD) methods. However, the obtained welded joints with similar properties to the base of UFG material are crucial for the production of finished engineering components. Conventional welding methods based on local melting of the joined edges cannot be used due to the UFG microstructure degradation caused by the heat occurrence in the heat affected zone…

Investigations on the Mechanical Properties and Formability of Friction Stir Welded and Laser Welded Aluminum Tailored Blanks

Improving friction stir welding of blanks of different thicknesses

Friction stir welding (FSW) appears to be a promising process even in the welding of blanks of different thicknesses. Actually, such particular tailor welded blanks (TWBs) are usually characterized by a reduction in ductility due to the utilized fusion welding process. In this paper the authors, starting from a preliminary feasibility study, investigate the possibility to improve the mechanical performances of friction stir welded blanks of aluminum alloy with different thicknesses. Both experiments and a FE analyses are developed for a few case studies with different thickness ratios between the blanks. The numerical investigations are performed with the aim to highlight the material tempe…

Design of Numerical Simulations of Linear Friction Welding Processes: Issues and Difficulties

In this paper, a critical analysis of the technical difficulties and numerical issues in running simulations of linear friction welding processes is carried out. The focus of the paper is the comparison of different modeling strategies of a numerical analysis for the LFW process of Ti-6Al-4V titanium alloy, for which the thermal aspect strongly influences the mechanical behavior due to the phase transformation, taking place over a definite range of temperature. A 3D simulation campaign, conducted using the FEA code DEFORMTM, was considered in order to show advantages and disadvantages of each approach, including the most critic limitations and complexity in a correct simulation design using…

On tool stirring action in friction stir welding of work hardenable aluminium alloys

In the paper solid state bonding conditions obtained in friction stir welding (FSW) of AA5754-H111 butt joints are analysed, considering the so called zigzag line in the transverse section of the joints. A wide experimental campaign was carried out varying both tool advancing speed and tool rotational one. The effects of the process on the mechanical properties of the joint were highlighted and micro- and macro-observations were used in order to explain the reasons of the enhanced mechanical properties found for the welded material. Numerical results derived from a FEM model previously developed by the authors were utilised to point out the different mechanical and metallurgical behavior of…

Mappe di Lavorabilita’ per Giunti Misti di Alluminio Mediante Processo di Saldatura Linear Friction Welding

Il Linear Friction Welding è un processo di saldatura allo stato solido in cui una parte fissa è forzata contro una parte che si muove con moto lineare alternato per generare calore attraverso l’attrito. Nel presente lavoro viene descritto lo studio effettuato per la realizzazione della giunzione mista mediante processo di Linear Friction Welding tra due leghe di alluminio che presentano proprietà meccaniche differenti, come la lega AA2011 e AA6082. Lo studio è stato condotto analizzando due differenti configurazioni determinate dalla posizione relativa delle leghe costituenti i provini da saldare. Per la realizzazione del processo è stata utilizzata una macchina prototipale dotata di senso…

Formability enhancement in incremental forming operations through sheet local heating

Fatigue characterization of hybrid joints CFRP-aluminum obtained by Self-Pierce Riveting (SPR)

Investigations on the Mechanical Properties and Formability of Friction Stir Welded Tailored Blanks

Tight competition characterizing automotive industries in the last decades has determined a strong research effort aimed to improve utilized processes and materials in sheet stamping. As far as the latter are regarded light weight alloys, high strength steels and tailored blanks have been increasingly utilized with the aim to reduce parts weight and fuel consumptions. In the paper the mechanical properties and formability of tailored welded blanks made of a precipitation hardenable aluminum alloy but with different sheet thicknesses, have been investigated: both laser welding and friction stir welding have been developed to obtain the tailored blanks. For both welding operations a wide rang…

Fatigue crack growth in 2024-T351 Friction Stir Welded Joints: longitudinal residual stresses and microstructural effects

Abstract The role of longitudinal residual stress on propagation of fatigue cracks was examined in friction stir welds produced in 2024-T351 aluminum alloy. Fatigue crack growth rate was obtained through constant Δ K Iapp tests for notches at different distances from the weld centerline. Subsequently, crack growth was correlated to weld residual stress measured by the cut-compliance method. It was found that residual stresses correspond to low crack growth rates outside the weld zone during fatigue loading. Once in the weld zone, the crack growth was affected by microstructural and hardness changes. Furthermore, weld residual stresses were mechanically relieved and effects on crack propagat…

Analysis of induced shape defects in FSW aluminum lap-joints for automotive applications

Single block 3D numerical model for linear friction welding of titanium alloy

A two-stage approach for the simulation of Linear Friction Welding is presented. The proposed model, developed using the commercial simulation package DEFORM, is 3D Lagrangian, thermo-mechanically coupled. The first phase of the process was modelled with two distinct workpieces, while the remaining phases were simulated using a single-block model. The Piwnik–Plata criterion was set up and used to determine the shifting from the dual object to the single-block model. The model, validated against experimental temperature measurements, is able to predict the main field variables distributions with varying process parameters. Titanium alpha and beta phases evolution during the whole process has…

Smart and resilient manufacturing in the wake of COVID-19.

Since 2020, manufacturers have been facing unprecedented and extraordinary challenges with the COVID-19 outbreak, which severely disrupted manufacturing operations around the world. Some manufac- turers have shifted gears to help address dire shortages during the coronavirus pandemic. Others were thrown into deep unknowns and faced with the grim prospect of being closed down. We have seen a sprawling network of multinationals and local businesses step in to fill a void by using 3D printers to make personal protective equipment (PPE) such as face shields, respirator masks, nasal swabs and even ventilator parts. Large manufacturers attempted to rejig parts of their production lines to mass-pr…

Ingegnerizzazione di una macchina prototipale per processi di saldatura linear friction welding

On the slabbing of stones throughdiamond wire cutting

Diamond wires are usually used in the cutting operations aimed to obtain slabs of stones. This tool consists of a steel cable on which are mounted annular metal–diamond pearls. The use of this technology expanded all over the world because of its advantages on other slabbing techniques as both technical and economical aspects are considered. It should be observed that with this technology wear phenomena must be properly monitored in order to obtain the best process conditions. Inthis article, thediamondwire cutting operation is investigated, highlighting the process mechanics and the wear phenomena occurring in the used tools. Furthermore, a modified version of the tool itself is proposed w…

Numerical prediction of Biphasic Titanium Alloys Microstructure in Hot Forging Operations.

Modern transportation industries shall comply with two demanding requirements: reducing operational consumption together with production costs coming from materials and labour. Current trend of engineering is oriented to meet both requirements increasing the rate of polymer matrix composites which implies association with structures made of titanium alloys. Hot forming can be used to reduce the production costs of titanium components: forging in closed dies of billets or semi finished form, in the temperature range where the Beta phase of titanium is stable, grants an adequate plasticity of the Ti-6Al-4V alloy, the most commercially used, allowing production of complex shapes with limited a…

Analysis of Joint Quality along Welding Plane

Porthole die extrusion is an always more important process for industrial applications. It is, however, characterized by a considerable complexity; in fact, different parameters have to be carefully set for improving the final part. A critical zone that strongly influences the goodness of the extruded component is the so called “welding plane”. It is the junction area where material flows converge inside the welding chamber. The variables that have to be controlled for improving the material characteristics in this zone are the effective stress, the pressure and the time that the material takes to cross the welding chamber. Moreover, material temperature is another fundamental issue that in…

AZ31 magnesium alloy recycling through friction stir extrusion process

Friction Stir Extrusion is a novel technique for direct recycling of metal scrap. In the process, a dedicated tool produces both the heat and the pressure to compact and extrude the original raw material, i.e., machining chip, as a consolidated component. A proper fixture was used to carry out an experimental campaign on Friction Stir Extrusion of AZ31 magnesium alloy. Variable tool rotation and extrusion ratio were considered. Appearance of defects and fractures was related to either too high or too low power input. The extruded rods were investigated both from the metallurgical and mechanical points of view. Tensile strength up to 80 % of the parent material was found for the best combina…

Influence of oblique edge blanking on the online punching quality after stretch bending

The oblique edge punching was proposed to reduce the surrounding sag failure occurred under the large punching force during online punching after stretch bending. The finite element models under three different kinds of punches were stablished and the punching processes were simulated by using the DEFORM-3D software. Comparison between the flat-edge punch and the oblique edge punches were realized, and the optimal height of the oblique edge of the unilateral bevelled punch and the single-peak bevelled punch were obtained. Three kinds of punches were designed based on the simulation results, and the experiments for manufacturing the upper strip of the automobile door frame by the online punc…

DETERMINAZIONE DELLE TENSIONI RESIDUE IN PROFILATI IN LEGA DI ALLUMINIO SALDATI DI TESTA MEDIANTE FRICTION STIR WELDING

Tool Path Design in Friction Stir Welding of AA6082-T6 Aluminium Alloy

In the paper, a variation of the Friction Stir Spot Welding (FSSW) process has been considered. In particular, a particular tool path is given after the sinking phase nearby the initial penetration site. The process mechanics was highlighted and the joint strength was considered at the varying of the most relevant process parameters. Furthermore macro and micro analyses were developed in order to highlight the process mechanics and the local material microstructure evolution. The investigated technology appears a promising joining technique in order to develop effective spot joints.

A new fixture for FSW processes of titanium alloys

FSW of titanium alloys is nowadays one of the most challenging welding operations, even with a solid state process, due to the thermo-mechanical and thermo-chemical characteristics of such materials. Due to the relevant application of titanium alloys in the aeronautic and aerospace industries, in the recent years few attempts were carried out to develop FSW processes aimed to maximize the mechanical performances of the welded parts. In the paper a new fixture is presented allowing obtaining effective FSW joints of titanium blanks, which were investigated through mechanical and metallurgical tests highlighting the peculiarities of FSW of titanium alloys.

An Innovative Friction Stir Welding Based Technique to Produce Dissimilar Light Alloys to Thermoplastic Matrix Composite Joints

Abstract Aluminum sheets can be joined to composite materials with different techniques. Each of them has advantages and weak points over the others. In literature, new techniques and patents are continuously developed to overcome these difficulties. In the paper a new Friction Stir Welding based approach is proposed to mechanically join AA6082-T6 to self-reinforced polypropylene. The aluminum sheet is pre-holed along both the sides of the weld line. A pinless tool generates the heat and pressure needed to activate back-extrusion of the composite. Joints have been produced with varying hole diameter and pitch. The mechanical resistance of the joint has been evaluated and the different failu…

Effective Linear Friction Welding Machine Redesign through Process Analysis

Linear friction welding is a solid-state joining process developed for non-axisymmetric components in which the joining of the specimens is obtained through reciprocating motion and pressure. In the process, the friction forces work due to the high frequency oscillation and the pressure between the specimens is converted in thermal energy. In order to design an effective machine, relevant issues derive from the high frequency and the large inertial forces involved in the process. In this study, the authors describe the redesign of a preexisting prototypal machine for LFW processes. A machine redesign is needed when welding high resistant materials, i.e. steels or titanium alloys, with high …

Application of a rheological Model for Phase Transformation Prediction in Beta Processing of Titanium Alloys

The paper shows a description of a numerical model able to simulate a complete forming process of Ti-6Al-4V titanium alloy that is a multi-phasic alloy composed, at room temperature, by two main different phases, namely Alpha and Beta, which evolve during both cooling and heating processes. The characterization of the material behavior concerns both the thermo-mechanical and metallurgical data in order to set a valid tri-coupled thermo-mechanical-metallurgical analysis systems taking into account the effects and interactions of all the phenomena resulting from the coupling of thermal, mechanical and metallurgical events. The numerical model was used to simulate a double numerical campaign r…

Friction Stir Welding of Magnesium Alloys under Different Process Parameters

Experimental study of SPR-bonded joints CFRP-AA2024-T6

Residual stresses and FCP prediction in FSW through a continuous FE model

Abstract Residual stresses prediction is definitively a relevant and open issue in welding processes. In the last years, different numerical models are proposed by many researchers to predict the residual stress field in FSW butt joint. However, most of these works are based on properly tuned analytical models and neglect the effect of the mechanical action due to the presence of the tool pin. In the present paper, a continuous 3D FE model, which was previously developed by some of the authors, was used to simulate the FSW process of butt joints with a single block approach, and predict the residual stress field by considering both thermal and mechanical actions. Then, the residual stress e…

Using a neural network for predicting the average grain size in friction stir welding processes

In the paper the microstructural phenomena in terms of average grain size occurring in friction stir welding (FSW) processes are focused. A neural network was linked to a finite element model (FEM) of the process to predict the average grain size values. The utilized net was trained starting from experimental data and numerical results of butt joints and then tested on further butt, lap and T-joints. The obtained results show the capability of the AI technique in conjunction with the FE tool to predict the final microstructure in the FSW joints.

Strumenti numerici avanzati per il cae di processi di formatura di leghe di titanio

Friction stir welding of stainless steel thin sheets in lap configuration

New research trends for Friction Stir Welding include the use of highly resistant materials as steels and titanium alloys. In the paper a continuum based FEM model for Friction Stir Welding of lap joint made out of thin stainless steel sheets is proposed, that is 3D Lagrangian implicit, coupled, rigid-viscoplastic. The model, whose potential has been analyzed though temperature distribution comparisons, is able to predict temperature, strain and strain rate distributions, with varying process variables. In this way the FEM model can be applied for effective process and tool design.

An overview of new joining technologies in aerostructures: laser beam welding and friction stir welding

New Trends in Manufacturing Processes Research 2020.

Multi-directional vs. mono-directional multi-step strategies for single point incremental forming of non-axisymmetric components

Abstract Multi Stage approach is used in Single Point Incremental Forming (SPIF) to overcome one of the main forming limitations, namely the maximum wall angle, characterizing the single stage process. In this paper, different multi-path strategies for the production of parts with flat edges are considered in order to evaluate the best solution in terms of feasibility and geometrical accuracy of the final part: A) mono-directional incremental draw angle; B) mono-directional incremental draw angle with increasing part side; C) Multi-directional approach with non-horizontal path planes. Strain evaluation by means of CGA (Circular Grid Analysis) and defect analysis have been carried out in ord…

Friction based solid state welding techniques for transportation industry applications

Comparison of analytical methods and AI tools for material characterisation in hot forming

Abstract Hot forming processes probably represent the most ancient of forming operations and what is more they are still today commonly used in modern mechanical industry in order to obtain sound parts, achieving large deformations with a limited required power. Hot metal forming operations are characterised by a large number of physical and thermal phenomena which have to be taken into account in order to model and design the processes themselves. Actually several thermally activated phenomena occur during the forming processes such as recovery, recrystallisation, grain growth, precipitation, allotropic transformations, etc. In this paper the comparison between an analytical method based o…

Residual stress measurement in innovative friction stir welding processes

In recent years, important innovations have been introduced in Friction Stir Welding (FSW) technology such as, for example, the Laser assisted Friction Stir Welding (LFSW) and in-process Cooled Friction Stir Welding (CFSW). Residual stresses have a fundamental role in welded structures because they affect the way to design the structures, fatigue life, corrosion resistance and many other material properties. Consequently, it is important to investigate the residual stress distribution in FSW where, though the heat input is lower compared to traditional welding techniques, the constraints applied to the parts to weld are more severe. The aim of the present work is to verify the capabilities …

Friction Stir Welding as an Effective Alternative Technique for Light Structural Alloys Mixed Joints

Abstract The increasing use of structural light alloys in the aeronautical, automotive and transportation industry is pushing researchers to find new solutions for the production of innovative components. Mixed joints made out dissimilar alloys represent a challenge for engineers to the difficulties arising in welding materials characterized by significantly different mechanical, thermal and chemical properties. In the paper, an overview of the most used process to produce dissimilar joints of aluminum, magnesium and titanium is given. Both fusion based and solid state welding processes can be used. Although the joining of these materials is possible, particular attention must be taken to t…

Influence of process parameters on the product integrity in friction stir extrusion of magnesium alloys

Friction Stir Extrusion is an innovative direct-recycling technology for metal machining chips. During the process a specifically designed rotating tool is plunged into a cylindrical matrix containing the scraps to be recycled. The stirring action of the tool prompts solid bonding related phenomena allowing the back extrusion of a full dense rod. This process results to be particularly relevant because allows the reuse of the scrap without any previous treatment. Experiments have been carried out in order to investigate the influence of the process parameters on the extrudes quality and a numerical model has been developed in order to simulate the evolution of the material flow.

Formability of friction stir welding AZ31 magnesium alloy sheets

FSW of AA2139-T8 Butt joints for aeronautical applications

The effect of process parameters on mechanical and microstructural properties of AA 2139 T8 joints produced by friction stir welding (FSW) was analysed by means of statistical tools. Three different parameters were taken into account: angular speed ( ω), welding speed ( va), and plunging depth ( p); each of them was varied on three levels. Forces and temperatures achieved during the welding were monitored and analysed for all joints. An accurate microstructural analysis was performed: the occurrence of some remarkable defects, typical of FSW, such as tunnel or lack of penetration, was related to actual process parameters adopted. The extension of each FSW characteristic zone was measured a…

Effetti delle tensioni residue sulla propagazione di cricche in giunti FSW in lega di alluminio

Materiali innovativi nella lavorazione di formatura delle lamiere nel settore automobilistico