Papers by Keyword: Metal Forming

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Authors: Jie Zhang, Abel Cherouat, Houman Borouchaki
Abstract: Metal orthogonal cutting and blanking are two important forming processes which include material removing. During finite element analyzing, the nonlinear problems of boundary, material and geometry must be considered to obtain the accurate calculating results. In this paper, we present an advanced adaptive remeshing procedure which has the capacities to simulate material removing processes in three dimensions. The sizes of finite elements are well adapted to local conditions which have the high distributions of physical fields using priori and posteriori error estimates. Based on constraint Delaunay Kernel, the unit mesh strategy is proposed to improve the mesh quality. By optimizing of both mesh edges and mesh elements, the mesh shape qualities are strictly controlled as the regular tetrahedrons. In this paper, Johnson-cook model is considered to simulate the elastic-visco-plastical material behaviors. The damage initiation is also judged by Johnson-cook criterion. The finite elements which reach the criterion will be killed and the material removing processes finished step by step. The proposed adaptive remeshing scheme is well present using the simulation of metal orthogonal cutting, milling and blanking processes.
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Authors: André Haufe, Andrea Erhart, Alexander Butz
Abstract: Due to their high strength (tensile strength > 1GPa) in combination with an extreme ductility (failure strain 30-50%) TWinning Induced Plasticity–steels (TWIP-steels) can be considered as promising materials for the production of lightweight automotive components. The industrial application of TWIP-steels requires a fundamental experimental validation of the mechanical behavior as basis for an user-friendly but at the same time accurate constitutive framework and its implementation into commercial Finite Element codes. Related investigations and implementations in order to allow for the simulation of TWIP-steel forming processes are currently conducted within the research project “TWIP4EU”, executed as a cooperation of Fraunhofer - Institut für Werkstoffmechanik IWM in Freiburg (Germany), Salzgitter Mannesmann Forschung GmbH (Germany), Swerea KIMAB (Sweden), Faurecia Autositze GmbH (Germany / France), DYNAmore GmbH (Germany) and ESI GmbH Engineering System (Germany / France).The monotonic one-dimensional hardening behavior of TWIP-steels as a function of the twin volume fraction and dislocation density has been described by Bouaziz et al. (2008), Bouaziz et al. (2011). This model has been proven to be adequate for the description of the flow behavior of TWIP-steels and serves as basis for the constitutive model, presented here. This Bouaziz-model has been extended to a three-dimensional elasto-plastic formulation, including the influence of different loading conditions, anisotropy and kinematic hardening. The present paper deals with the implementation for solids and shells in the commercial Finite Element Code LS-DYNA® and appropriate validation simulations will be presented.
411
Authors: Heng Sheng Lin, Sheng Chi Tsai, Yuan Chuan Hsu, Ming Che Hsiao, Chia Chou Ke, Bean Yin Lee
Abstract: The manifolds of airbag inflator were used to be produced by sheet-metal forming. It comprised at least eleven forming stages to achieve its final shape. Uneven wall thickness and poor dimensional accuracy were the common defects because the planar anisotropy of sheet-metal caused earing on the cup rim. In this study, the cup-shape workpiece is obtained from backward-extrusion of billets, followed by two stages of end-forming of tube and three stages of hole-piercing. During the end-forming production, the tool life of the first forming stage was the most severe because it applies close-die forging to increase its rim thickness. Therefore, in addition to the design of prestressed die insert, special attendance is paid to the partition of the die insert to further alleviate the stress level. The optimization of die insert was aided by the finite element analysis of DEFORM software. The results show that by lowering the parting line, the stress level can be minimized. The tool life can therefore be improved.
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Authors: Yong Ming Guo
Abstract: Point collocation methods have no mesh, no integration. While, the robustness of the point collocation methods is an issue especially when scattered and random points are used. To improve the robustness, some studies suggest that the positivity conditions can be important when using the point collocation methods. For boundary points, however, the positivity conditions cannot be satisfied, so that it is possible to get large numerical errors from the boundary points when using the point collocation methods. The author has proposed a point collocation method with a boundary layer of finite element. In this method, by introducing a boundary layer of finite element in boundary domain of workpiece, unsatisfactory issue of the positivity conditions of boundary points can be avoided, and the complicated boundary conditions can be easily imposed with the boundary layer of finite element. A forging process is analyzed by using the point collocation method with a boundary layer of finite element.
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Authors: Marion Merklein, Andreas Maier, Daniel Kinnstätter, Christian Jaremenko, Emanuela Affronti
Abstract: The forming limit diagram (FLD) is at the moment the most important method for the prediction of failure within sheet metal forming operations. Key idea is the detection of the onset of necking in dependency of different sample geometry. Whereas the standardized evaluation methods provides very robust and reliable results for conventional materials like deep drawing steels, the determined forming limits for modern light materials are often too conservative due to the different failure behavior. Therefore, within this contribution a new and innovative approach for the identification of the onset of necking will be presented. By using a pattern recognition-based approach in combination with an optical strain measurement system the complete strain history during the test can be evaluated. The principal procedure as well as the first promising results are presented and discussed.
333
Authors: Fei Han, Mathias Liewald
Abstract: Because of the extensive use of thin sheet metals to reduce the weight of vehicles, wrinkling is becoming a more common and one of the most undesirable failures in the sheet forming process. Generally, experiments for studying wrinkling phenomena can be divided into two methods: actual forming of typical parts such as annular cup test on the one hand and the tests of specially designed sample geometries like the Yoshida Buckling test on the other. Recent experiments indicate that the plastic strains at the onset of wrinkling in the Buckling Test with Yoshida samples are too small to reflect reality of deep and stretch drawing conditions. Therefore, in this paper, in order to enhance the accuracy of the prediction of wrinkling, a new modified Yoshida specimen is provided for numerical simulation. The fundaments of the different buckling phenomena are going to be explained considering the energy theory in metal forming processes. Meanwhile, the influences of the changeable sample geometries in order to cause different stress distribution within loaded area of specimen have been investigated.
199
Authors: M. Foroutan, M. Mortazavi
Abstract: In this paper a rigid plastic mesh free method for slightly compressible materials is presented for the simulation of bulk metal forming processes. In this model MLS shape functions are used for the approximation of velocity field. These shape functions are defined in initial coordinates of particles. By using this method the support of shape functions covers the same set of particles during material deformation. Transformation method is used for imposition of essential boundary conditions. Transformation matrix is formed only once at the initial stage, because shape functions are defined in initial coordinates system. For evaluation of the presented model, disk upsetting and ring upsetting processes are simulated. Results obtained from this model are compared with experimental data and FEM results and good agreement is observed between them.
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Authors: Reimund Neugebauer, Verena Psyk, Christian Scheffler
Abstract: To make the advantages of electromagnetic forming applicable for industrial manufacturing, a three step tool design strategy is suggested. At first, simplified decoupled electromagnetic and structural mechanical simulations are used for creating a preliminary design via a systematic iterative optimization process. The selected design is verified in more accurate coupled simulations. A prototypic realization serves for further optimization, if necessary. The applicability of the approach is proved on the basis of an inductor system for magnetic pulse welding of tubes.
333
Authors: Yong Ming Guo, Kenji Nakanishi
341
Authors: Esmeray Üstünyagiz, Mohd Hafis Sulaiman, Peter Christiansen, Chris Valentin Nielsen, Niels Bay
Abstract: The trend in metal forming tribology is to develop new tribo-systems including new lubricants, tool materials and tool coatings in order to substitute environmentally hazardous lubricants by environmentally friendly tribo-systems. In preliminary testing the limits of lubrication of new tribo-systems for sheet forming production, it is advantageous to use dedicated simulative tribo-tests. This paper studies the influence of tool coatings on deep drawing operations using the Bending Under Tension (BUT) test and also under more severe tribological conditions by adopting the Strip Reduction Test (SRT) to replicate industrial ironing of deep drawn, stainless steel parts. Non-hazardous tribo-systems in form of a double layer Diamond-like coated tool applied under dry condition or with an environmentally friendly lubricant were investigated via emulating industrial process conditions in laboratory tests. Experiments revealed that the double layer coating worked successfully, i.e. with no sign of galling, when it was used with environmentally friendly lubricants, whereas the results were more prone to galling under dry condition.
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