On the effectiveness of numerical simulation in the prediction of profile distortion in extrusion

Among the so-called ‘traditional processes’, extrusion represents one of the most diffused and utilized, since it permits the production of many industrial parts and raw materials. Of course, relevant knowledge on process mechanics and practice is nowadays available in the technical literature and in properly constructed handbooks. On the other hand, the introduction of finite element simulation, as a powerful analysis and design tool, opened new perspectives. Nowadays many researchers are involved in research tasks aimed at explaining some peculiar extrusion aspects. In this paper the effectiveness of numerical simulation for a complex three-dimensional extrusion process analysis is inves…

A force measuring based strategy for failure prevention in incremental forming

Abstract Incremental forming processes show a number of advantages compared to the traditional processes but, at the same time, some drawbacks are clearly known. Current problems, include the slowness of the process, low accuracy and a lack of knowledge in the field of material formability. This paper is focused on the latter issue: an industrially oriented methodology for detecting the approach of failure in incremental forming is proposed. The approach is based on the analysis of the trend of the forming force in order to assess whether the process can be run safely. If not, a proper strategy, to avoid material failure, is proposed and experimentally validated.

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 …

Development of an Extrusion Equipment to Measure Force and Pressure in Hollow Components Manufacturing

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…

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.

Some remarks on material formability in single point incremental forming of sheet metal

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

Assessment of some relevant local variables in machining using the split-tool technique

H and P Mesh Refinement in the Metal-Forming F.E.M. Analysis

In this paper a comparison between H and P refinement techniques in the metal-forming F.E.M. analysis is carried out in order to evaluate their computational efficiency. The results are compared using a particular error estimator which locally allows determining the workpiece zones where the refinement is necessary.

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…

Energy and Resource efficient Forming Processes

On the springback prediction in 3d sheet metal forming processes

Numerical and Experimental Investigation on Hot Impression Die Forging: Flash Design Optimisation

In forging processes, several parameters have a great influence on the quality of the final product: complexity of the product geometry, lubricating conditions, temperature, preform shape. The main objective of a forging design process is to ensure an adequate material flow aimed to obtain a defect free component minimizing material losses, forging loads and tool wear. In this paper, the problem of optimising the flash geometry in hot forging is studied with particular reference to flash thickness and flash–land width. The main goals to be pursued concern the minimization of the flash volume (i.e. the surplus of material necessary to fill the die cavity), with the aim to reduce material los…

Wear modelling in mild steel orthogonal cutting when using uncoated carbide tools

Abstract Wear prediction in machining has been recently studied by FEM although the use of numerical methods for such applications is still a very challenging research issue. In fact, wear phenomenon involves many aspects related to process mechanics which require a very accurate modelling. In other words, only a very punctual code set-up can help the researchers in order to obtain consistent results in FE analysis. The high relative velocity between chip and tool requires effective material models as well as friction modelling at the interface. Moreover the prediction of temperature distribution is another critical task; in the paper some different procedures are discussed. Subsequently a …

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.

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…

Internal pressure and material feeding optimisation in tube hydroforming

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 Laboratory Scale Equipment to Relieve Force and Pressure in Cold Extrusion of Lead Hollow Components

Nowadays, many researchers are involved in studies aimed to the explanation of some peculiar aspects regarding manufacturing processes. In this paper, an experimental campaign was carried out in order to reproduce tube extrusion starting from a cylindrical billet. In particular, the development of a proper equipment is presented: the aim was to measure both the total load, by using the testing machine load cell, and the local pressure value on the porthole. The latter task was carried out performing a proper system based on the use of a small load-cell. The tube was extruded with a good surface quality and the external area does not show any welding line evidence. Pure Lead was used for the…

Computer-Aided Simulation of Die Filling Processes

Summary A numerical method for analysing the filling of axisymmetrical dies of complex shape is proposed. The method, which is a further development of a LP finite element model, is able to take into account the contact conditions directly in the mathematical formulation of the problem. In such a way the solution of the die filling process is obtained by solving a LP problem, avoiding problems of numerical convergence and the heavier calculations requested by other iterative methods.

Measurement of tool temperatures in orthogonal cutting by means of thermography techniques

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…

Stato dell’arte del Friction Stir Welding

Optimisation of a tube hydroforming process by gradient techniques

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…

Mobility, Data, and Behavior: The TrafficO2 Case Study

This chapter presents the social innovation project “TrafficO2”, a support system for decision-making in the field of transportation that tries to push commuters towards more sustainable mobility by providing concrete incentives for each responsible choice. After focusing on Palermo, Italy, the context of this case study, this chapter provides a detailed description of the TrafficO2 model. Specifically, the chapter deals with the analysis of a selected sample of users among Palermo University students who commute daily to their respective University departments on campus. Starting from the modal split of the actual situation (Status Quo scenario), another behavior scenario (Do your right mi…

A gradient based technique for costs minimisation in impression die forging

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 …

Experimental campaign to assess numerical simulation of tool wear in orthogonal cutting

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…

A simple inverse procedure to determine heat flux on the tool in orthogonal cutting

The applications of numerical simulation to machining processes have been more and more increasing in the last decade: today, a quite effective predictive capability has been reached, at least as far as global cutting variables (for instance cutting forces) are concerned. On the other hand, the capability to predict local cutting variables (i.e. stresses acting on the tool, temperature distribution, residual stresses in the machined surface) has to be furtherly improved, as well as effective experimental procedures to validate numerical results have to be developed. The aim of this paper is the proposition of an innovative approach, based on an simple inverse procedure, in order to identify…

The effects of cryogenic cooling on surface integrity in hard machining: A comparison with dry machining

A Critical Analysis on the Friction Modeling in Orthogonal Cutting of Steel

Numerical simulation of cutting process is today moving towards two different directions. The former concerns the development of high performance codes able to approach the 3D phenomena, the latter is already focused on the study of some fundamental aspects whose full understanding may be strategic for the knowledge enhancing in this very complex field. In the paper this second way was pursued and a wide analysis on the numerical robustness of the 2D orthogonal cutting process is presented. In particular, the role played by the friction modeling is discussed taking into account a wide integrated numerical and experimental campaign.

On the FE codes capability for tool temperature calculation in machining processes

Abstract The applications of numerical simulation to machining processes have been more and more growing in the last years: today a quite effective predictive capability has been reached, at least as far as global cutting variables (for instance cutting forces) are concerned. On the other hand, the capability to predict local cutting variables (i.e. pressure on the tool, temperature distribution, residual stresses in the machined surface) has to be heavily improved and verified. At the same time, effective experimental procedures for validating numerical results have to be developed. In this work two different approaches were implemented for temperature measuring: a thermocouple based appro…

Analysis of stamping performances of dual phase steels: A multi-objective approach to reduce springback and thinning failure

The industrial interest on light weight components has contributed in the last years to a significant research effort on new materials able to guarantee high mechanical properties, good formability and reasonable costs together with reduced weights when compared to traditional mild steels. Among such materials advanced high strength steels (AHSS) such as transformations induced plasticity (TRIP) and dual phase (DP), and light weight alloys proved their usefulness in stamping of automotive components. As AHSS are concerned, one of the main drawbacks is related to springback occurrence. Many aspects have to be taken into account when springback reduction is investigated: material behavior iss…

An Intelligent Tool to Predict Fracture in Sheet Metal Forming Operations

One of the main issues in sheet metal forming operations design is the determination of formability limits in order to prevent necking and fracture. In fact, the ability to predict fracture represents a powerful tool to improve the production quality in mechanical industry. Many researchers investigated the problem here addressed, mainly studying forming limit diagrams (FLD) or developing fracture criteria which are able to foresee fracture defects for different processes. In this paper, the author present some early results of a research project focused on the application of artificial intelligence (AI) for ductile fracture prediction in sheet metal forming operations. The main advantage o…

Analisi numerico sperimentale del processo di piegatura di Tubi

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 …

Sheet Thinning Prediction in Single Point Incremental Forming

Incremental forming processes are characterized by a well known and particular feature: any deformation across the sheet plane determines sheet thinning, since the blank is fully clamped by means of a proper equipment. As a consequence, the availability of effective and reliable CAE tools capable to supply an accurate prediction of sheet thinning as a function of process parameters, represents a strong requirement for a wider practical application of incremental forming. The already available theoretical models (i.e. the sine law) do not provide, on the other hand, satisfactory results. Therefore in the paper a couple of numerical analysis strategies was applied to simulate simple increment…

A Pareto optimal design approach for simultaneous control of thinning and springback in stamping processes

One of the most relevant research issues in automotive field is focused on the reduction of stamped parts weight also increasing their strength. In this way, a strong research effort is developed on high strength steels which are widely utilized and they require a proper springback control. Springback reduction in sheet metal forming is a typical goal to be pursued which is conflicting with thinning reduction for instance. Thus, such problems can be considered as multi-objective ones characterized by conflicting objectives. What is more, nowadays, a great interest would be focused on the availability of a cluster of possible optimal solutions instead of a single one, particularly in an indu…

Asymmetric Single Point Incremental Forming of Sheet Metal

The use of computers in manufacturing has enabled the development of several new sheet metal forming processes, which are based upon older technologies. This paper describes modifications that have been made to traditional forming methods such as conventional spinning and shear forming, forming processes in which deformation is localized. Recent advances have enabled this localized deformation to be accurately controlled and studied. Current developments have been focused on forming asymmetric parts using CNC technology, without the need for costly dies. Asymmetric Incremental Sheet Forming has the potential to revolutionize sheet metal forming, making it accessible to all levels of manufac…

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…

An overview of sustainability issues in manufacturing and building sector: a life cycle assessment approach

In the latest decades, the industrial consumption of materials and energy has undergone a growth which may exceed the limits of earth resources. Therefore, a strong awareness of the need to use materials and energy in a more efficient way has arisen. A wide research interest on sustainability is present in the modern technical literature: Life Cycle Assessment (LCA) methodology and Design for Environment (DFE) procedures are nowadays widely investigated in many research labs all over the world. In this context, this paper focuses on LCA approaches in two main fields: manufacturing and building sector. As the former is regarded, sustainability issues are crucial topics and the reduction of e…

Square Ring Compression: Numerical Simulation and Experimental Tests

In the upsetting process of square rings buckling problems often arise, depending on the geometry of the ring and on the frictional conditions at the punch-workpiece interface, yielding to the practical unacceptability of the forged component. Consequently in order to make up a set of rules to be introduced in an expert system able to assist the designer of cold forming sequences, a knowledge base has been built up, by means of a set of numerical simulations, the results of which have been validated by several experimental tests.

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 …

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

Improving surface integrity of additively manufactured GP1 stainless steel by roller burnishing

Abstract Additive manufacturing can rapidly fabricate the desired components by selectively melting and solidifying feedstock, rather than conventional subtractive machining. However, the difference between the two routes in terms of surface integrity of the final component is relevant. This paper presents a strategy to control the surface characteristics of additively manufactured stainless steel by roller burnishing. In particular, process parameters have been carefully selected to improve the surface integrity of the worked material. The quality of the surface has been analyzed in terms of roughness, hardness, microstructure and residual stresses. The overall product endurance under high…

Numerical analysis for formability boundaries definition in sheet metal forming operations

Formability limits in sheet metal forming have been widely investigated through different approaches. The main aim of such approaches was to develop tools able to prevent or predict fracture occurrence in order to improve production quality. Forming limit diagrams (FLDs) and fracture criteria are probably the most utilised tools in this field; nevertheless, some drawbacks of such tools were demonstrated. In particular, forming limit curves are characterised by ineffective prediction capability if non linear deformation paths are taken into account. Moreover, the importance of stress paths was demonstrated in order to predict fracture, and forming limit stress diagrams are, nowadays, deeply …

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

On the Use of Artificial Neural Networks to Predict Ductile Fracture for Different Materials

An inverse procedure to determine heat flux on the tool in orthogonal cutting

Asymmetric Single Point Incremental Forming of sheet metal

The use of computers in manufacturing has enabled the development of several new sheet metal forming processes, which are based upon older technologies. This paper describes modifications that have been made to traditional forming methods such as conventional spinning and shear forming, forming processes in which deformation is localized. Recent advances have enabled this localized deformation to be accurately controlled and studied. Current developments have been focused on forming asymmetric parts using CNC technology, without the need for costly dies. Asymmetric Incremental Sheet Forming has the potential to revolutionize sheet metal forming, making it accessible to all levels of manufac…

Prediction of Ductile Fractures in Metal-Forming Processes: an Approach Based on the Damage Mechanics

The Authors propose a new approach for the prediction of ductile fractures in bulk metal forming processes: the approach is based on a numerical analysis able to take into account damage occurrence and evolution in constitutive equations. The model supplies the distribution of the void volume fraction in the workpiece during the deformation path: consequently, the comparison to a critical value, determined by means of a simple tension test, allows to predict the growth of defects. The proposed approach has been applied to the drawing process: the numerical results have been compared with a set of experimental tests showing a good predictive capability of the model.

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.

Hot Impression Die Forging Process: An Approach to Flash Design for Tool Life Improvement

In impression die forging the role of the flash geometry is fundamental since a proper design of the flash land strongly influences both the complete die filling and the die wear (i.e. the die life and the related costs). In this paper an integrated approach between numerical simulations and statistical tools was developed with the aim to optimize flash thickness in order to reduce die wear and to minimize material wasting. As wear is regarded, an analytical model depending on sliding velocity, temperature, die hardness and contact pressure was utilized during the numerical simulations of the process in order to reach a wear evaluation for different values of the flash design variables. Thu…

WEAR PERFORMANCE OF CERAMIC CUTTING-TOOL MATERIALS WHEN CUTTING STEEL

Abstract Some test cycles have been carried out in continuous cutting conditions, employing cutting parameters (feed, depth of cut and cutting speed) chosen following experimental planes and suitable test fields. The wear tests have been carried out on AISI 1040 steel with cutting speeds from 5m/sec to 11m/sec. The silicon nitride, sintered carbide, cubic boron nitride and alumina reinforced with SiC whiskers inserts, have shown, at each assigned cutting parameter, poor wear resistance when cutting steel. Alumina and alumina in submicron grain, which has been toughened by ZrO2 phase transformation, and the oxide-based alumina, have been the better wear resistance. The mixed based alumina ha…

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.

Prediction of ductile fracture in bulk metal forming: an artificial neural networks based approach

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…

Process parameters calibration in 3D tube hydroforming processes

In tube hydroforming the concurrent actions of pressurized fluid and mechanical feeding allow to obtain tube shapes characterized by complex geometries such as different diameters sections and/or bulged zones. What is crucial in such processes is the proper design of operative parameters aimed to avoid defects (for instance shape defects or ductile fractures). The main process parameters are material feeding history (i.e. the punches velocity history) and internal pressure path during the process. In more complex three dimensional processes, also the action of a counterpunch is generally useful to reduce thinning in particular in expansion zones of the tube (i.e. T or Y shaped tubes). The g…

Uno Smart Campus per UniPA

L’accesso pervasivo alla rete ha avviato una profonda trasformazione del tessuto sociale e culturale, incidendo profondamente anche sui processi di erogazione dei servizi della Pubblica Amministrazione. L’Università degli Studi di Palermo si inserisce in tale contesto, avendo recentemente intrapreso un percorso di innovazione che mira ad espandere i confini della didattica, della divulgazione del sapere scientifico, della creazione di nuova scienza e cultura, al fine di creare uno Smart Campus pronto ad accogliere gli studenti ormai “nativi digitali”.

The effects of cryogenic cooling on surface integrity in hard machining: A comparison with dry machining

Abstract This paper presents results of an experimental study of cryogenic machining of hardened AISI 52100 steel, focusing on surface integrity. Experiments were performed under dry and cryogenic cooling conditions using CBN tools varying cutting speeds, workpiece hardness and tool geometry. Surface integrity parameters (surface roughness, white layer thickness, residual stresses, metallurgical conditions including grain size, phase transformation, etc.) were investigated to establish the effects of cryogenic cooling on the surface integrity of the machined component, and results were compared with those from dry hard machining. Overall, cryogenic cooling provides improved surface integrit…

Material Substitution for Automotive Applications: A Comparative Life Cycle Analysis

Lightweight materials have become an important strategy in the automotive industry to enable vehicle weight reduction and reduce fuel consumption. However, when developing specific strategies, the overall benefits of any material should be analyzed throughout its life cycle to comprehend energy/environmental differences that arise during its processing and its final use. A key example is aluminum which despite having great potential in the use phase requires large amounts of energy to process. This paper provides a comparison between aluminum and steel utilizing a life-cycle approach. This approach reveals the importance of incorporating a recycling strategy to leverage aluminum’s low-weigh…

On the correlations between friction model and predicted temperature distribution in orthogonal machining

On the finite element simulation of thermal phenomena in machining processes

Machining processes are frequently investigated by numerical simulations. Usually 2D analyses are carried out in order to reduce CPU times, considering orthogonal cutting conditions. In this way, the computational time sharply reduces and many process variables may be calculated (i.e. forces, chip morphology, shear angle, contact length). On the other hand, the analysis of thermal aspects involved in machining, for instance the temperature distribution reached in tool, still represents an open problem. Finite element codes are able to simulate a very short process time that is not sufficient to reach steady state conditions. Several approaches have been proposed to overcome this problem: in…

Analysis of metal spinning processes by the ADINA code

Abstract The ADINA code, version 84, has been employed for the analysis of sheet spinning processes. The main process parameters have been evaluated in different working conditions; namely for various geometries and constitutive laws of the material.

Finite element analysis of the thermo-mechanical behaviour of coated tools in mild steel machining

Moving Least Squares Innovative Strategies For Sheet Forming Design

In the last years a great interest in optimization algorithms aimed to design forming processes was demonstrated by many researches. Proper design methodologies to reduce times and costs have to be developed mostly based on computer aided procedures. Response surface methods (RSM) proved their effectiveness in the recent years also for the application in sheet metal forming aiming to reduce the number of numerical simulations. Actually, the main drawback of such method is the number of direct problem to be solved in order to reach good function approximations. A very interesting aspect in RSM application regards the possibility to build response surfaces basing on moving least squares appro…

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.

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…

Wear Modeling in Orthogonal Cutting Using Coated Tools

Dependance of machining simulation effectiveness on material and friction modelling. That’s why industrial application of machining simulation is still so far

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…

Optimal die Design for Cold Extrusion Processes

The design of cold extrusion processes requires the optimisation of several process variables in order to obtain a defect free product. The fulfilment of different objectives, such as the minimisation of forming loads or the homogeneity of the deformations, is highly requested. Nevertheless, several other relevant aspects of extrusion processes have to be taken into account and require a suitable optimisation of the process parameters and in particular of the die shape. In this paper, tool life has been assumed as the most relevant goal and an effective die design procedure as been setup. It is well known that fatigue cracking of the dies is the principal cause of dies failure in cold extru…

Computer simulation of metal flow in the hot upsetting of a high-strength aluminium alloy

Abstract The effects of metal-working temperature on the hot axisymmetric upsetting of AA 7012 aluminium alloy were investigated in the temperature range of from 250 to 400°C, at a strain rate of 4 s −1 . The material behaviour was studied by means of simulative methods based on the analysis of torsion-test results which have shown that when the strain increases, the flow stress increases to a peak value and then decreases to a fracture value. Furthermore, the flow stress decreases with decreasing strain rate and with increasing temperature. Constitutive equations, describing accurately the hot deformation behaviour of the material, were defined and used subsequently in a numerical model th…

Assessment of material models through simple machining tests

The accuracy of the results obtained from FEM simulation of machining operations depends on the accuracy of input data. Among these, the flow stress data of the workpiece are extremely important together with the friction along the tool-chip interface. In this study, an identification procedure for the determination of material parameters that are used for the FEM simulation of machining processes is proposed. The procedure is based on the coupling of a numerical identification procedure and Arbitrarian Lagrangian Eulerian (ALE) Finite Element simulations of turning operations. An experimental campaign was developed in order to calibrate the model and to validate the procedure. The basic id…

On the sustainability evaluation in sheet metal forming processes

In sheet metal forming processes there is still a lack of knowledge in the field of environmental sustainability mainly due to the need of a proper modeling of issues and factors to be taken into account. Such topic is, nowadays, a urgent and remarkable issue in manufacturing and the main concerns are related to more efficient use of materials and energy. What is more, the estimation of environmental burdens of forming technologies is very complex to be accomplished since it is essentially process-dependent. This means that when comparing, for instance, a traditional forming process with an innovative one, there are some peculiar aspects to be considered; actually, processes can be rather d…

An integrated approach to the design of tube hydroforming processes: artificial intelligence, numerical analysis and experimental investigation

In the last years, the growing role of process flexibility in modern mechanical industries has driven a rising interest in optimisation of process/product design through innovative techniques. Moreover, the development of niche productions, which are characterised by low production volumes and small batches leads to the need of more flexible and rapid forming technologies. In this way, a great research effort is performed towards the study of new stamping processes: among them hydro forming finds a large interest in automotive industry since it allows to significantly reduce tooling costs and also to avoid some secondary operations. Different studies are available in the technical literatur…

On the evaluation of the global heat transfer coefficient in cutting

The use of numerical simulations for investigating machining processes is remarkably increasing because of the simulation cost is lower than the experiments and the possibility to analyze local variables such as pressures, strains, and temperatures is allowable. Process simulation is very hard from a computational point of view, since it frequently requires remeshing phases and very small time steps. As a consequence, the simulated cutting time is usually of the order of few milliseconds and no steady cutting conditions are generally achieved, at least as far as thermal conditions are concerned. Therefore, nowadays numerical prediction of cutting temperatures cannot be considered fully reli…

On the Computational Error in 3D Simulation of Cutting

An analytical model for improving precision in single point incremental forming

Abstract In the modern manufacturing scenario and, in particular, in sheet metal forming, the requirement of customised production is still growing. The introduction of incremental forming enables the production of customised components in small lots. In particular, single point incremental forming is characterised by the simplest equipment; any die, in fact, is avoided reducing the necessary tooling to a simple frame, able to clamp the sheet, and a hemispherical punch that imposes the required deformation. This tooling simplicity and the associated process mechanics, in turn, determine a sometimes relevant lack of accuracy. The paper is focused on the investigation of the influence of the …

INTERNAL PRESSURE AND COUNTERPUNCH ACTION DESIGN IN Y-SHAPED TUBE HYDROFORMING PROCESSES: A MULTI OBJECTIVE OPTIMISATION APPROACH

In sheet metal forming most of the problems are multi-objective problems, generally characterised by conflicting objectives. A classical approach to investigate such kind of problems is focused on a combination of multiple objectives into a unique objective function to be optimised. Actually, in metal forming processes optimisation two main phases have to be developed in order to reach an optimal solution: the former is the modelling phase (definition of the design variables and objective function) and the latter concerns the computational aspect (numerical simulations or experiment to be developed). In this paper, an integration between numerical simulations, response surface methodology a…

Realizzazione di prodotti in lamiera mediante formatura incrementale

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

Utensile di saldatura per attrito

Error Estimates and Automatic Adaptive Mesh Refinement for the Metal Forming FEM Analysis

The Authors propose a new technique which enables a estimation of the error inherent with the FEM analysis of metal forming processes. The aim is to evaluate the zones where the error is higher in order to proceed to a refinement of the mesh in such zones, and to obtain a smaller value of the global error. Moreover, to simplify the analyst work in the progressive refinement of the mesh, it has been prepared a software able to read the drawing created by a CAD program and to generate, automatically, all the geometrical and topological data necessary to perform the analysis on Personal Computer. The automatic renumbering of the elements in the refined mesh has been performed with the aim to r…

Innovative flexible sheet forming

Energy consumption analysis of robot based SPIF

Part of: Seliger, Günther (Ed.): Innovative solutions : proceedings / 11th Global Conference on Sustainable Manufacturing, Berlin, Germany, 23rd - 25th September, 2013. - Berlin: Universitätsverlag der TU Berlin, 2013. - ISBN 978-3-7983-2609-5 (online). - http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-40276. - pp. 131–136. Production processes, as used for discrete part manufacturing, are responsible for a substantial part of the environmental impact of products, but are still poorly documented in terms of environmental impact. A thorough analysis of the causes affecting the environmental impact in metal forming processes is mandatory. The present study presents an energy consumption anal…

Optimal Design of Tube Hydroforming Processes: a Fuzzy Logic Based Approach

A gradient based approach for the design of the shape of the blank in deep drawing of rectangualr boxes

On-Line Control of Single Point Incremental Forming Operations through Punch Force Monitoring

Abstract Among the innovative sheet metal forming processes, Single Point Incremental Forming (SPIF) represents the simplest and the cheapest one. Despite its relevant advantages, up to now no specific CAE tools for SPIF were developed and the tool trajectory is generally defined utilizing CAD/CAM software developed for machining applications. In the paper an innovative monitoring and control approach, aimed to define and in-process update the most relevant process parameters during an industrial SPIF operation, is proposed. The strategy utilizes as monitoring variable the punch force trend: a set of preliminary tests demonstrated, in fact, its suitability as “spy variable” of the process m…

Finite element simulation of friction stir welding

Limits of the Open-Die Forward Extrusion: Numerical Analysis and Experimental Tests

In the paper the open-die forward extrusion process is analysed in order to determine the influence of the most important geometrical and frictional parameters on the practical suitability of the operation. Experimental tests have been carried out and their results have been compared with the numerical ones derived by FEA.

Optimisation strategies to determine process parameters in tube hydroforming

A critical analysis on the friction modelling in orthogonal machining

Abstract Despite the development of high performance finite element-based codes, the simulation of machining still represents a very hard task due to the geometric complexity of the real chip-tool systems and the high cutting speed that requires very long simulation times. For these reasons, many aspects related to machining are not very clear and so easy to simulate. In this paper a rigorous investigation on the role played by the implemented friction model within a 2D simulation of orthogonal cutting was carried out, taking into account different models proposed by the researchers in the last years. The main simulation results were compared with experimental measurements in order to verif…

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…

An Inverse Approach for the Design of the Optimal Preform Shape in Cold Forging

Abstract In closed die forging the preform design plays a critical role for the success of the process: in fact it must ensure that in the finishing step the desired product is obtained without shape defects such as underfilling or folding and with a minimum material loss into the flash. In the paper an inverse approach is applied to the preform shape optimization problem: the method permits to evaluate a response function which links the set of parameters defining the preform shape with the fulfillment of the product design specifications. The proposed approach has been applied to a closed die forging process aimed to the production of a C-shape component, and has allowed to determine the …

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…

Deep Drawing Process Design: A Multi Objective Optimization Approach

In sheet metal forming most of the problems are multi objective problems, generally characterized by conflicting objectives. The definition of proper parameters aimed to prevent both wrinkles and fracture is a typical example of an optimization problem in sheet metal forming characterized by conflicting goals. What is more, nowadays, a great interest would be focused on the availability of a cluster of possible optimal solutions instead of a single one, particularly in an industrial environment. Thus, the design parameters calibration, accomplishing all the objectives, is difficult and sometimes unsuccessful. In order to overcome this drawback a multi-objectives optimization procedure based…

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

Enhancements in sheet incremental forming and friction joining technologies

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…

3D finite element analysis of tool wear in machining

Abstract The paper is focused on the 3D numerical prediction of tool wear in metal cutting operations. In particular, an analytical model, able to take into account the diffusive wear mechanism, was implemented through a specific subroutine. Furthermore, an advanced approach to model heat transfer phenomena at the tool–chip interface was included in the numerical simulation. The adopted simulation strategy gave the possibility to properly evaluate the tool wear. The 3D FEM results were compared with some experimental data obtained turning AISI 1045 steel using uncoated WC tool; a good agreement was found out.

Modelling of Cutting and Machining: 10 years of ESAFORM activity

This paper reports on the state of the art in the simulation of cutting and machining processes. The contributions provided by researchers all over the world and published on the Proceedings of the European Scientific Association for material FORMing (ESAFORM) Conferences are highlighted. They role played by ESAFORM in this field of research has been quite active, as demonstrated by the number of contributions, their relevant scientific content and finally by the vitality of the minisymposium on Modeling of Machining that has been organized since 2001 with no interruptions.

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…

ALE Simulation of Orthogonal Cutting: a New Approach to Model Heat Transfer Phenomena at the Tool-Chip Interface

This paper presents a new procedure to evaluate the global heat transfer coefficient in orthogonal cutting. The knowledge of the actual heat transfer conditions is a fundamental issue as far as the life, tool wear and tool substitution interval are regarded. More in detail, an Arbitrary Lagrangian-Eulerian approach was utilised to model orthogonal cutting process and the numerical simulations were validated by making experimental tests for identifying cutting forces and internal tool temperatures. A mild steel was cut utilising both an uncoated (WC) and a coated (TiN) tool. On the basis of both experimental and simulative data, a consistent model of the global heat transfer coefficient as f…

On the springback prediction in industrial air bending sequences

Shape and dimensional accuracy in Single Point Incremental Forming: State of the art and future trends

Abstract The paper is aimed to discuss some relevant issues concerning an innovative sheet metal forming technology, namely Single Point Incremental Forming. The advantages of this technology are addressed, including its capability to provide effective answers to some impellent industrial requirements: process flexibility, strong customer orientation, production of highly differentiated goods at low industrial costs. As well some relevant drawbacks are highlighted, mainly as concerns the level of accuracy permitted by the process. A wide recognition of the research efforts in this field is presented, taking into account some general considerations on the difference sources of shape and dime…

On the Sustainability Evaluation in Sheet Metal Forming Processes

In sheet metal forming processes there is still a lack of knowledge in the field of environmental sustainability mainly due to the need of a proper modeling of issues and factors to be taken into account. Such topic is, nowadays, a urgent and remarkable issue in manufacturing and the main concerns are related to more efficient use of materials and energy. What is more, the estimation of environmental burdens of forming technologies is very complex to be accomplished since it is essentially process-dependent. This means that when comparing, for instance, a traditional forming process with an innovative one, there are some peculiar aspects to be considered; actually, processes can be rather d…

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.

Optimal closed die finish forgings for Nimonic 105 using FEM method

FE Analysis of Tool Wear in Orthogonal Cutting

Sustainability issues in sheet metal forming processes: an overview

Abstract Environmental sustainability in manufacturing is nowadays an urgent and remarkable issue and the main concerns are related to more efficient use of materials and energy. In sheet metal forming processes there is still a lack of knowledge in this field mainly due to the need of a proper modelling of sustainability issues and factors to be taken into account. The aim of this paper is mainly to underline the state of the art from a forming point of view about the sustainability contributions offered in any phase of a product life cycle. Actually, a lack in terms of comprehensive contributions is present in the technical literature, thus, the authors try to give a sort of holistic visi…

Processi di taglio: valutazione numerica delle tensioni residue

Sheet incremental forming: a new process configuration allowing controlled flow of the sheet material under the blank-holder

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…

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

La formatura superplastica di leghe di Titanio per l'impiego aeronautico

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…

A Study on the Correlations between Machining Parameters and Specimen Quality in WEDM

Wire electrical discharge machining (WEDM) is widely used in manufacturing, medical, aircraft applications and, virtually, all areas of conductive material machining. The process involves a series of very complex electrical, thermodynamical and electromagnetical phenomena that are still partially unknown. Due to the large amount of parameters involved in the process, a suitable set-up of the variables aimed to obtain the best performance is often very difficult. In the paper the results of a wide experimental analysis are presented: the tests were carried out on high-speed steel and tempered steel specimens utilising brass wires. The influence of the most important process parameters on the…

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…

Knowledge-Based Systems and F.E. Simulations in Metal-Forming Processes Design An integrated Approach

Summary The automatic computer aided planning and design of cold forming processes includes several phases, among which the most important are the optimal choice of the forming operations sequence and, for each operation, the determination of the more suitable operating parameters. With this aim the Authors propose an integrated approach based on the preliminary choice of some feasible forming sequences, carried out by means of a knowledge-based system, and on the subsequent determination of the optimal one employing a finite element simulation of the process.

A sensitivity analysis on artificial neural networks fracture predictions in sheet metal forming operations

Ritorno elastico in processi di formatura della lamiera

Optimal design of tube hydroforming processes: A fuzzy-logic-based approach

In recent years, tube hydroforming has become an economic and industrially suitable alternative to various traditional stamping processes, in particular for small batch production. In the present paper, an artificial intelligence system based on fuzzy logic was implemented for tube hydroforming process design. The aim was to achieve a process design procedure able to prevent forming defects and guarantee the achievement of the desired final shape of the component. In particular, the process design concerns the internal pressure history and the axial feeding. The fuzzy system is able to provide optimal trajectories for both the controlled parameters, producing a defect-free final part.

An Experimental Investigation of Residual Stresses in Hard Machining of AISI 52100 Steel

In this paper an experimental investigation was conducted to determine the effects of the tool cutting-edge geometry, workpiece hardness, cutting speed, and microstructural changes (white and dark layers) on the residual stresses in dry orthogonal hard machining of AISI 52100 steel. X-ray diffraction technique was used to obtain in-depth residual stresses profiles in both axial and circumferential directions. The results show that tool geometry, workpiece hardness and cutting parameters significantly affect the surface residual stress, maximum compressive residual stress below the machined surface and its location. Moreover, microstructural analysis shows that thermally-induced phase transf…

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…

Formatura della lamiera: il processo incrementale

Prediction of Tool Wear Progress in Machining of Carbon Steel using different Tool Wear Mechanismsl

In this paper the prediction of tool wear on carbide uncoated tools was taken into account. In particular, two different tool wear models based on the diffusion mechanism and on the abrasion mechanism were considered. The calibration of the utilized models was done using the results obtained by experimental analysis performed on an orthogonally machined AISI 1020 tube. Once the calibration was executed, numerical simulations, for both the utilized tool wear models, were simultaneously performed with the aim to test the capability of the proposed numerical procedure. The comparison between the two tool wear mechanisms for predicting the flank tool wear is discussed in the paper.

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

On the effectiveness of numerical simulation in the prediction of profile distorsion in extrusion

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…

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…

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…

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 …

Ottimizzazione numerico sperimentale di un processo di estrusione a freddo

On the effectiveness of Finite Element simulation of orthogonal cutting with particular reference to temperature prediction

Abstract Finite Element simulation of orthogonal cutting is nowadays assuming a large relevance; in fact a very large number of papers may be found out in technical literature on this topic. In recent years, numerical simulation was performed to investigate various phenomena such as chip segmentation, force prediction and tool wear. On the other hand, some drawbacks have to be highlighted; due to the geometrical and computational complexity of the updated-Lagrangian formulation mostly used in FE codes, a cutting time of only a few milliseconds can be effectively simulated. Therefore, steady-state thermal conditions are not reached and the simulation of the thermal phenomenon may be ineffect…

Three-dimensional FE simulation of single point incremental forming: experimental evidences and process design improvements

Application of the Neural Network technique for reducing springback in Incremental Forming processes

Analysis of the punch force in incremental forming for revealing failure approaching

On the use of artificial intelligence tools for fracture forecast in cold forming operations

Abstract The design of cold forming processes requires the availability of a procedure able to deal with the prevention of ductile fracture. In fact, the ability to predict fracture represents a powerful tool to improve the production quality in mechanical industry. In this paper, artificial intelligence (AI) techniques are applied to ductile fracture prediction in cold forming operations. The main advantage of the application of AI tools and in particular, of artificial neural networks (ANN), is the possibility to obtain a predictive tool with a wide applicability. The prediction results obtained in this paper fully demonstrate the usefulness of the proposed approach.

Neural network based approach for improving geometrical precision in Incremental Forming

Deep drawing process parameter design: a multi objective optimization approach

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 …

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

Numerical prediction of elastic springback in automotive complex parts

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…

Prevedere la frattura duttile nello stampaggio a freddo

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…

Cross Extrusion With Asymmetric Die: A Comparison Between Finite Element and Meshless Formulation Predictions

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…

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…

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.

DEPENDENCE OF MACHINING SIMULATION EFFECTIVENESS ON MATERIAL AND FRICTION MODELLING

Numerical simulation of cutting processes is still a very difficult matter, although some relevant geometrical simplifications and high-performance codes are used. A large number of technical papers have been focused on the predictive capability of the codes: nevertheless the prediction quality is not very satisfactory if the problem is analyzed in a wide sense. In this paper the simple orthogonal cutting process of a plain-carbon steel is investigated taking into account different process conditions (cutting speed and feed rate). Furthermore, four material constitutive equations and three friction models were implemented and a sensitivity analysis was carried out comparing the numerical pr…

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…

Some considerations on the precision of incrementally formed double-curvature sheet components

Severe plastic deformation (SPD) processes for metals

Abstract Processes of severe plastic deformation (SPD) are defined as metal forming processes in which a very large plastic strain is imposed on a bulk process in order to make an ultra-fine grained metal. The objective of the SPD processes for creating ultra-fine grained metal is to produce lightweight parts by using high strength metal for the safety and reliability of micro-parts and for environmental harmony. In this keynote paper, the fabrication process of equal channel angular pressing (ECAP), accumulative roll-bonding (ARB), high pressure torsion (HPT), and others are introduced, and the properties of metals processed by the SPD processes are shown. Moreover, the combined processes …

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.

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

Verso il Dieless: la Formatura Incrementale

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…

A depth dependent analytical approach to determine material breaking in SPIF

Formability is a relevant issue in Single Point Incremental Forming (SPIF) process since it is one of the main point of strength together to the possibility to avoid any dedicated die. Several researches agree that, depending on working material and process parameters, in SPIF operations there is a threshold slope of the wall that cannot be overcame without material breaking. If deep Incremental Forming is taken into account, despite the previous statement it is possible to demonstrate that, when the threshold angle is imposed, there is a relation between the actual workpiece depth and the material breaking approaching. In this paper, the latter relationship was investigated and formally de…

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…

Rapid Prototyping through the application of AISF technique

A preliminary comparison between finite element and meshless simulations of extrusion

In this paper the extrusion process of a cross-shaped profile was investigated. In particular, the study was focused on the distortion of extruding profiles when the workpiece and die axis are not aligned. The process was simulated using the finite element method (FEM) and the natural element method (NEM), both implemented in an updated-Lagrangian formulation, in order to avoid the burden associated with the description of free surfaces in ALE or Eulerian formulations. Furthermore, an experimental equipment was developed in order to obtain reliable data in terms of deformed entity, required process load and calculated pressure. At the end, a comparison between the numerical predictions and …

Central Bursting Defects in Drawing and Extrusion: Numerical and Ultrasonic Evaluation

Abstract A new approach for the prediction of central bursting defects in extrusion and drawing is proposed: a finite element analysis of the processes has been carried out, and the obtained results have been elaborated by means of a post-processor, which, employing a proper ductile fracture criterion, is able to suggest if and where the central burst occur. An ultrasonic control system able to detect the insurgence of defects with a resolution of 0.2 mm. has been setup in order to verify the predictive capability of the model. The experimental results show a good agreement with the numerical predictions confirming the effectiveness of the proposed approach, whose industrial application app…

Materiali innovativi nella lavorazione di formatura delle lamiere nel settore automobilistico