Experimental studies on uniaxial and echibiaxial tensile tests applied to plastic materials sheets
Abstract The main objective of this paper is to determine the behavior of few plastic materials using two different type of tests. We use classical uniaxial tensile test to determine the most important mechanical and elastic characteristics, such as: yield stress, Young modulus, tangent modulus, maximum stress and maximum strain and to plot engineering stress vs. engineering strain curve for these materials. The second test, that was used in this study, was echibiaxial tensile test on the spherical punch. This test was used to determine maximum breaking force and, of course maximum displacement of specimen on punch direction and others few important characteristics, such as: major and minor…
Common defects of parts manufactured through single point incremental forming
Single point incremental forming is one of the most intensely researched die-less manufacturing process. This process implies the usage of a CNC equipment or a serial robot which deforms a sheet metal with the help of a relatively simple tool that follows an imposed toolpath. As every cold metal forming process, besides the many given advantages it has also some drawbacks. One big drawback in comparison with other cold metal forming processes is the low accuracy of the deformed parts. The aim of this research is to investigate the sheet metal bending mechanism through finite element method analysis. The results shows that the shape of the retaining rings has a big influence over the final g…
Comparative Study by Numerical Analysis on the Formability of Deep-Drawn Tailor-Welded Blanks
The realising of complex parts by welding together and then deep-drawing metal sheets made of different steel types or even different metal types can have many advantages, such as decreasing the part’s weight, reducing the manufacturing costs and an increased dimensional precision. In order to benefit from these results, a detailed knowledge of the metal sheets’ behaviour during deep-drawing is necessary. The current paper aims to compare, using numerical simulations based on the finite element method, the deep-drawing behaviour of parts made of steel sheets of different thicknesses welded together in three different manners and also of a part made of a monoblock blank.
Experimental Studies Regarding the Mechanical Behaviour of Silicon-Coated and Uncoated P.A. 6.6 Fabrics
These paper aims to present an experimental study for determining the mechanical properties of woven fabrics used for airbags manufacturing. In order to realise the study, there were chosen two types of fabric, one that is coated with silicon and one that is uncoated. The experimental tests that were carried out were uniaxial tension tests for samples extracted on the warp and on the weft direction, the Bias test, a test specific for shear loads and the dome test, a test specific for biaxial loads. For the uniaxial tension test the force-displacement curve was obtained and the maximum values of the loads and the displacement. For the last two tests (bias test and dome test) there have been …
Simulated 3-axis versus 5-axis Processing Toolpaths for Single Point Incremental Forming
Abstract Accuracy and productivity of the parts manufactured by single point incremental forming (SPIF) are influenced by the proper selection of toolpaths. CAM software packages are often used for generating the toolpaths for the process. Literature survey have revealed that contour curves and spatial spirals are the most used toolpaths for SPIF. These toolpaths are generated using 3-axis approaches, meaning that the tool axis is maintained parallel to the vertical axis. The 3-axis approach was justified using 3-axis CNC milling machines as the main technological equipment for SPIF. However, nowadays, the wide spreading of both 5-axis CNC milling machines and industrial robots, with far su…
Mechatronic Contouring System for Unconventional Sheet Metal Forming Processes
This paperwork was developed in order to present the work concerning the use of mechatronic approach in the study of motion control systems for metal forming processes. The paper presents the use of low cost motion control systems, based upon induction motors, as driving systems in unconventional sheet metal forming processes. The main goal of this work was to implement a 2D contouring system for driving the active plate. The model of the system, simulations and some experimental work will be presented.
COMPARATIVE ANALYSIS OF RIGID AND FLEXIBLE STRUCTURES OF THE ECCENTRIC PRESSES
Abstract The aim of this paper is to make a comparative study of the static behaviour of the eccentric presses, using the finite elements method, on the rigid structure and on the flexible structure, respectively. The finite elements modelling of the component elements of the presses are done in two ways: node by node link type (rigid structure) or using a linking element spring damper type (flexible structure). On these two structures there is successively applied a number of static analyses, in order to determine the strain of working area and the design of the stiffness graph.
Single point incremental forming: An assessment of the progress and technology trends from 2005 to 2015
The last decade has seen considerable interest in flexible forming processes. Among the upcoming flexible forming techniques, one that has captured a lot of interest is single point incremental forming (SPIF), where a flat sheet is incrementally deformed into a desired shape by the action of a tool that follows a defined toolpath conforming to the final part geometry. Research on SPIF in the last ten years has focused on defining the limits of this process, understanding the deformation mechanics and material behaviour and extending the process limits using various strategies. This paper captures the developments that have taken place over the last decade in academia and industry to highlig…
Theoretical and Experimental Studies on the Influence of Process Parameters on Strains and Forces of Single Point Incremental Forming
These paper aims to determine the influence of the most important geometrical parameters (vertical step and punch diameter) on the main strains, thickness reduction and the forces along two directions during the single point incremental forming process (SPIF). The paper comprises a comparative numericalexperimental study, for a simple geometry part obtained by incremental forming. In fact, in the first stage, the punch has a vertical motion with the value of one vertical step. In the second stage, the punch follows a linear trajectory along one side of the die. After each linear trajectory the punch has successive vertical motions, taking one vertical step at a time until the entire geometr…
Using an Adaptive Network-based Fuzzy Inference System to Estimate the Vertical Force in Single Point Incremental Forming
Manufacturing processes are usually complex ones, involving a significant number of parameters. Unconventional manufacturing processes, such as incremental forming is even more complex, and the establishment of some analytical relationships between parameters is difficult, largely due to the nonlinearities in the process. To overcome this drawback, artificial intelligence techniques were used to build empirical models from experimental data sets acquired from the manufacturing processes. The approach proposed in this work used an adaptive network-based fuzzy inference system to extract the value of technological force on Z-axis, which appears during incremental forming, considering a set of…
Experimental Studies Regarding Mechanical Behaviour of Textile Reinforcements Laminated Composite Materials
The aim of this paper is to determine the mechanical properties of textile reinforcements laminated composite material and to establish the influence of thickness about these properties. The composite material used for this is a laminated sheet of HGW 2082. In order to study the mechanical behaviour of these kinds of materials we select two experimental tests: uniaxial test and bending test. For the uniaxial test we have measured the maximum load, the maximum extension, the maximum tensile stress and the maximum tensile strain. Also, using an optical extensometer we measured the major and the minor strains. For the bending test we measured the maximum load and the maximum bending deflection…
Experimental Determining of Mechanical and Elastic Characteristics for the Material Used in the Manufacturing of Cardan Crosses
The paper presents in its first part the need for analysing the functioning of the cardan cross within the cardan transmission, both from the point of view of shape and from the point of view of the material. In the second part there are described the main elements for analysing the test samples, the employed testing machine, as well as the manner of processing the obtained information. The last part contains the conclusions resulted from this analysis..
Method for improving the contouring accuracy for CNC profiling machines at the shop floor level
Computer Numerically Controlled (CNC) laser cutting machines are capable of producing high-quality precise parts. However, as cutting speeds is increased, in order to achieve higher productivity, the accuracy of the parts is affected. In order to improve the contouring accuracy of these machines, a simple straight-forward joint simulation and experimental strategy is proposed. The position controllers within the feed drives are considered the key factor in improving the dynamic behavior and consequently the contouring accuracy of a CNC laser cutting machine at the shop floor level.
Comparative Study for Springback Prediction on Single Point Incremental Forming Process
The present paper proposes a comparative study in order to determine the springback in single point incremental forming process. Using the Ls-Dyna software the process was simulated for one piece in frustum of pyramid shape. In the end of the explicit dynamic analysis, it was run, using the same software, an implicit analysis to determine the springback. For this comparison study we selected four different shell formulations. The results obtained in this simulation were compared with those obtained experimentally for the same part. The experimental research was conducted on a robot and, on the opposite side of the machined surface, an Aramis measuring optical system was placed to allow the …
Biomechanical Study of the Osteoporotic Spine Fracture: Optical Approach
Background and objectives: Osteoporotic spine fractures represent a significant factor for decreasing quality of life in the elderly female population. Understanding the mechanisms involved in producing these fractures can improve their prevention and treatment. This study presents a biomechanical method to produce a vertebral fracture, conducted on a human spine segment, observing the displacements and strains in the intervertebral disc, endplate, and vertebral body. Materials and Methods: We performed two tests, one corresponding to an extension loading, and the second to an axial loading. Results: The maximum displacement in the target vertebral body presented higher values in the case o…
Advanced Techniques used in Numerical Simulation for Deep-drawing Process
The present paper analyse the main characteristics of the numerical simulation by finite element method of the deep-drawing processes. Also the authors’ highlights the mathematical apparatus and the calculus method used for numerical simulations of metal forming processes in many of the current simulation software. The authors present the capabilities of the inverse analysis, direct analysis, implicit analysis (for springback simulation) and the optimisation analysis applied to explicit formulations.
Aspects of Improving the Cost-Performance Ratio for the Manufacturing of Small-Size Cast Parts
Abstract The paper analyses some of the commercially available solutions for casting small-size metallic parts and outlines possible solutions that would reduce the cost of such systems while maintaining a high performance level. high performance level. One typical application area for small-size parts is human prosthetics, so the commercial casting machines analysed here are used mainly in this application domain. The paper shows how high-cost systems added to the machines for providing protective atmospheres can be replaced by low-cost solutions with the same results in terms of part quality. Moreover, a solution is described that avoids the typical drawbacks of the currently used casting…
Inverse Analysis Used to Determine Plastic Flow and Tribological Characteristics for Deep-drawing Sheet
Abstract The present paper aims to develop a simple method based on inverse analysis that allows us to determine the laws of plastic flow coefficients and the friction coefficient between the material and punch. Selecting from different types of tests, we have chosen the Hecker test, because this test requires a single form of punch, the hemispherical one. In this test, the friction between the punch and the blank-sheet is caused by the blank-sheet strains and not by the movement it makes (as in deep drawing case). Besides the friction coefficient, other parameters like hardening and strength coefficients (n and k), influence the distribution of stresses and strains in the material. Using t…
Motion control systems for machine tools - a mechatronic approach by means of simulation
Tuning the control parameters of the feed drives for existing state of the art CNC machine tools, or retrofitting obsolete machine tools requires a close understanding of the position control process. The use of a mathematical model of the feed drive, combined with a computer simulation process is needed in order to fulfill the above mentioned tasks. In this paper some simulation tools for studying the CNC motion control systems are presented. Both single axis positioning regime and biaxial linear and circular interpolation regime were taken into consideration. The main goal of the research was to offer a handson integrated simulation tools compatible and able to use for improving the perfo…
Optical study for springback prediction, thickness reduction and forces variations on single point incremental forming
Abstract The goal of the present work is to present an experimental study regarding the influence of the main technological influence factors such as the vertical step and the punch diameter on the single point incremental forming process (SPIF). In this paper we estimate the influence of these two factors on springback, thickness reduction and forces. Both parameters were varied on two levels: (d) punch diameter 6 and 10 mm and (s) vertical step 0,1 and 0,5 mm. The experiments were done on experimental layout composed by a robot, a clamping system that contains the die’s lower part and the optical system.
Experimental Study Regarding of Bending Behaviour of Stabilizator Link
Abstract This paper presents an experimental study of the behavior of anti-roll power link subjected to bending, power link coming from an Opel Astra G. The power link is made of PA66 GF30 polyamide. For this study, there were used a universal testing machine (Instron 5587) and a real-time strain measurement optical system (Aramis). The results showed are those obtained in the case of a compression force of 1,000 [N] namely: major Strain ε1, minor strain ε2, equivalent von Mises strain, displacement on X axis, displacement on Y axis (compression force direction), displacement on Z axis.
Numerical Study about the Influence of Wall Angle about Main Strains, Thickness Reduction and Forces on Single Point Incremental Forming Process
Abstract The current paper aims to study, using numerical simulation, the influence of the wall angle on the single point incremental forming process. For the analysis there has been used the LS-Dyna software and three explicit dynamic analyses were run for three parts with wall angles of 450, 550 and 650. The factors taken into account are the main strains, the thickness reduction and the forces on three directions. The material data introduced into the simulation were determined based on an uniaxial traction test on an Instron 5587 testing machine and the Aramis system was used as optical extensometer.
Experimental Study Regarding PA and PE Sheets on Single Point Incremental Forming Process
The present paper aims to present an experimental study on the behaviour of PA and PE sheets during the single point incremental forming. Due to the fact that the purpose of this research is to study the behaviour of PA and PE sheets during the single point incremental process both in terms of process forces and in terms of major and minor strain and thickness reduction, a Kuka Kr210 robot was chosen as an alternative to using a universal milling machine. The specimens were made of 3 mm PA and PE sheets. The size of the sheets was 250 mm x 250 mm. The forces measured on the three directions of the coordinate axes were compared. To measure the major strain, minor strain and thickness reducti…
Computer Simulation for the Study of CNC Feed Drives Dynamic Behavior and Accuracy
In the application of CNC feed drives it is desirable to predict the servo performance. By using computer simulation techniques it is possible to construct an accurate model of the servo drive. This simulation procedure makes it possible to anticipate machine design problems and correct them. This paper deals with a model of a feed drive, which consists of a motion control system driven by a DC motor. Both position and velocity feedback loops are present in the structure of the system. By means of MATLAB & Simulink software, simulation diagrams were built in order to test the behaviour of the system. Experimental data are also presented in order to confirm the accuracy of the theoretical mo…
ROUGHNESS CONTROL OF PARTS OBTAINED THROUGH INCREMENTAL SHEET FORMING
Abstract The present paper adresses the issue of controlling the quality of surface in the case of a new sheet metal forming process by which various curved shells are formed without the help of expensive dies. The roughness of the surface which comes in direct contact with the punch at incremental sheet forming suffers an obvious worsening compared to the initial blank surface roughness. The present paper discusses the measuring of the roughness of parts obtained through the previously mentioned process and highlights the factors that influence it. There were taken into account the initial roughness of the punch, the punch diameter and the friction coefficient between the punch and the bla…
Influence of Geometrical Parameters, Wall Angle and Part Shape on Thickness Reduction of Single Point Incremental Forming
Abstract The aim of this paper is to study the thickness reduction during the whole single point incremental forming process. The experimental setup is realized in such a way that the blank sheet is in the vertical position and forming is done using an anthropomorphic robot with six degrees of freedom. The vertical positioning of the blank sheet allows the on-line visualization using an optical measuring system of the major and minor strains and of the thickness reduction. The wall angle varied between values of 45 0 , 55 0 and 65 0 respectively. The logarithmic major strain and minor strains and logarithmic thickness reduction were analyzed in order to allow a comparison with values obtain…
Modular device used in the surgery of the human tibia
Simulation approach for improving CNC milling machines accuracy for single axis motion
CNC milling machines are widely used in manufacturing processes. In time, their accuracy is decreasing, which directly influences the accuracy of the manufactured parts. This research proposes a simulation-based method for improving the accuracy of the above mentioned machines, which is suitable to be applied at the shop floor level. A model of the feed drive, using a dc servomotor as actuator, is the core of the proposed approach. Matlab & Simulink based simulation diagrams were built in order to test the behavior of the system.
Single-Point Incremental Forming of Titanium and Titanium Alloy Sheets.
Incremental sheet forming of titanium and its alloys has a significant role in modern manufacturing techniques because it allows for the production of high-quality products with complex shapes at low production costs. Stamping processes are a major contributor to plastic working techniques in industries such as automotive, aerospace and medicine. This article reviews the development of the single-point incremental forming (SPIF) technique in titanium and its alloys. Problems of a tribological and microstructural nature that make it difficult to obtain components with the desired geometric and shape accuracy are discussed. Great emphasis is placed on current trends in SPIF of difficult-to-fo…
Motion control of medium size CNC machine-tools-A hands-on approach
This paperwork presents an integrated approach based upon simulation and experimental work for reducing the positioning errors of a small to medium size CNC machine-tools. The approach is intended to be used at the shop-floor level and therefore it is based upon a straight-forward model of the feed drive. The model was particularized with specific data from a CNC milling machine and simulation techniques were used to predict the behavior of the system. Only the control parameters of the feed drive which may be altered by the user, without modifying the structure of the CNC controller were taken into consideration and tuned. Simulation results and experimental data gathered before and after …