Papers by Keyword: Rigid Plastic FEM

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Authors: D.H. Jang, Beong Bok Hwang, Sun Keun Hwang, Kyung Hoon Min, Hyoung Jin Choi
Abstract: A frictional contact model is adopted for the analysis of conventional solid rivet setting. Material properties for the selected plates and rivets are obtained from analytical method using elastic constants and tensile strengths for each material. Rigid- and elasto-plastic models are selected for process analysis in this paper. Process variables are selected to investigate the effect of variables on the successful rivet setting and servicing in any structure as force transmitting member. Major variables in riveting process are material variables such as material properties and geometrical variables, which are dimensions of head, shank, and blank diameters. Analysis in this study is concentrated on the influence of variety of materials and of shank dimensions on the contact area after rivet setting, i.e. after forming process of rivet head. Soft and hard materials are selected as mother materials to investigate how the selection of material influences on the riveting process in quantitative manner. The geometry of head is closely investigated through simulation in terms of contact status, i.e. contact area between rivet head and mother material, which would affect the snap fit joint by riveting.
Authors: Beong Bok Hwang, G.M. Lee, Y.H. Lee, J.H. Ok, S.H. Kim
Abstract: In the present study, the finite element analysis has been conducted to investigate the deformation characteristics of forward and backward can extrusion process using AA 1100 aluminum alloy tubes in terms of maximum forming load and extruded length ratio in a combined material flow. A commercially available code is used to conduct rigid-plastic FEM simulation. Hollow tubes are selected as initial billets and the punch geometries follow the recommendation of ICFG. Selected design parametrs involved in simulation includes punch nose radius, die corner radius, frictional condition, and punch face angle. The investigation is foucused on the analysis of deformation pattern and its characteristics in a forward tube extrusion combined simultaneously with backward tube extrusion process main in terms of force requirements for this operation according to various punch nose radii and backward tube thickness. The simulation results are summarized in terms of load-stroke relationships for different process parameters such as backward tube thickness, die corner radii, and punch face angle, respectively, and pressure distributions exerted on die, and comparison of die pressure and forming load between combined extrusion and two stage extrusion process in sequencial operation. Extensive analyses are also made to investigate the relationships between process parameters and extruded lengths in both forward and backward directions. It has been concluded from simulation results that a) the combined operation is superior to multi-stage extrusion process in sequential operation in terms of maximum forming load and maximum pressure exerted on die, b) the length of forward extruded tube increases and that of backward extruded tube decreases as the thickness ratio decreases, and c) the forming load is influenced much by the thickness ratio and the other design factors such as die corner radius and punch face angle does not affect much on the force requirement for the combined extrusion process.
Authors: Yong Ming Guo
Abstract: In this paper, a rigid-plastic hybrid element method is formulated, which is a mixed approach of the rigid-plastic domain-BEM and the rigid-plastic FEM based on the theory of slightly compressible plasticity. Since compatibilities of velocity and velocity's derivative between adjoining boundary elements and finite elements can be met, the velocity and the derivative of velocity can be calculated with the same precision for this hybrid element method. While, the compatibility of the velocity's derivative cannot be met for the rigid-plastic FEMs.
Authors: Chan Chin Wang
Abstract: A simulator based on rigid-plastic finite element method is developed for simulating the plastic flow of material in forging processes. In the forging process likes backward extrusion, a workpiece normally undergoes large deformation around the tool corners that causes severe distortion of elements in finite element analysis. Since the distorted elements may induce instability of numerical calculation and divergence of nonlinear solution in finite element analysis, a computational technique of using the Euler’s fixed meshing method is proposed to deal with large deformation problem by replacing the conventional way of applying complicated remeshing schemes when using the Lagrange’s elements. With this method, the initial elements are generated to fix into a specified analytical region with particles implanted as markers to form the body of a workpiece. The particles are allowed to flow between the elements after each deformation step to show the deforming pattern of material. The proposed method is found to be effective in simulating complicated material flow inside die cavity which has many sharp edges, and also the extrusion of relatively slender parts like fins. In this paper, the formulation of rigid-plastic finite element method based on plasticity theory for slightly compressible material is introduced, and the advantages of the proposed method as compared to conventional one are discussed.
Authors: Jiang Xin Zhu, Jian Xin Deng
Abstract: This paper presents a rigid-plastic finite element method for orthogonal cutting process by adopting Lagrange method. The rigid-plastic FEM analysis model is established and the rigid-plastic FEM analysis toolkit was developed. Meanwhile, two relevant key problems are discussed systematically, including the rule of chip-workpiece separation and the criterion of tool-chip separation. At last, a simulation example of planing an aluminium alloy (ZL-301) workpiece was conducted. The effects of the cutting stroke, the tool rake angle and the friction coefficient on chip were observed. The numerical simulation results have a good agreement with their experimental ones. It is indicated that the presented FEM model and algorithm are efficient and correct.
Authors: Dong Hwan Jang, J.H. Ok, H.S. Koo, G.M. Lee, Beong Bok Hwang
Abstract: The rigid-plastic finite element method has been applied to three variants of radial extrusion processes to investigate the influence of die geometry on the material flow into the flange gap. Case I involves forcing a cylindrical billet against a flat die, which is a single action pressing process. In case II, another single action pressing process, the upper punch forces a billet against a stationary punch recessed in the lower die. Both the upper and lower punches move together in Case III toward the center of billet at the same speed with a double action tool. Major process parameters are identified as the relative gap height and the die corner radius in constant relative deformation. The relative gap height is defined as the ratio of gap height to billet diameter. Extensive simulation work for various combinations of process parameter value has been performed and then the main characteristics of the deformation patterns of each case are observed to define the terms which represent the forming characteristics of the flange in radial extrusion processes in terms of separation height, asymmetric ratio of height, and asymmetric ratio of angle, respectively. The effect of major process parameters on the material flow into the flange gap has been also analyzed in terms of flange radius and flange angle. The effect of frictional condition on the separation height has been also analyzed to investigate the edge separation of flange from the flat die. AA 6063 aluminum alloy is selected as a model material throughout the analysis. Simple comparison between AA 6063 and AISI 1006 steel has been also made to investigate the effect of material selection on the deformation pattern, especially in terms of separation height in Case I and asymmetry in Case II, respectively.
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