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The present work is concerned with three-dimensional finite element analysis of the hollow section extrusion process using a porthole die. The effects of related design parameters are discussed through the finite element simulation for extrusion of a triply-connected rectangular tubular section. For economic computation, mismatching refinement, an efficient domain decomposition method with different mesh density for each subdomain is implemented. In order to obtain the uniform flow at the outlet, design parameters such as the hole size and the hole position are investigated and compared through the numerical analysis. Comparing the velocity distribution with that of the original design, it is concluded that the design modification enables more uniform flow characteristics. The analysis results are then successfully reflected on the industrial porthole die design. [ABSTRACT FROM AUTHOR]

An easy and robust grid-based approach is proposed to construct the fully hexahedral mesh in three-dimensional case and its application for the mesh regeneration or remeshing during the finite element simulation of a metal forming process is presented to show the validity and effectiveness of the scheme. The proposed scheme enables the construction of the provisional mesh by superimposing the regular cubical grid over the object to be meshed and removing the exterior grid points and cells. Because the constructed provisional mesh has the discrete rugged boundary that is quite different from the boundary geometry of the object to be meshed, the nodes on the boundary of the provisional mesh are projected onto the object boundary. The main disadvantage of the mesh constructed by grid-based approaches is its severely distorted elements on the boundary owing to the projection of the rugged boundary onto the object boundary. In order to improve the quality of boundary elements, some layers of elements on the boundary surface are constructed and the nodes are repositioned by mesh smoothing. Consequently, the quality of boundary elements is effectively improved. [ABSTRACT FROM AUTHOR]

Two kinds of time integration methods; the dynamic explicit method and the static implicit method, have been compared, especially with emphasis on the shell formulations and the stress integration methods. Two methods have been applied to the benchmark problem named the S-rail stamping process, provided by NUMISHEET'96 committee, in order to compare their numerical results with each other and with the average values of the experiments as well. Based on the comparisons, it is shown that both time integration methods can be successfully applied to industrial sheet metal stamping simulations. In detail, the static implicit method is advantageous over the dynamic explicit method in terms of accuracy, while the latter is known to be more efficient than the former in terms of computation efficiency. [ABSTRACT FROM AUTHOR]

A new method of three-dimensional remeshing is proposed for thermo-viscoplastic finite element analysis of connecting rod forging. In the method, the deformed body to be remeshed is divided into a surface-adaptive layer (SAL) and a core region. At the surface layer of hexahedral elements, the arrangement of nodal points is made by normal projection of boundary nodes in order to retard the mesh degeneracy, since the arrangement of boundary nodes can be easily achieved by using the information of the die surface patch. After generating the mesh automatically at the surface-adaptive layer, the core region is automatically meshed by introducing a body-fitted mapping technique. In order to show the effectiveness of the method in the three-dimensional problem, forging of a connecting rod has been simulated as a practical example. The complete simulation of connecting rod forging has been carried out by using the thermo-viscoplastic finite element method and the remeshing scheme. The analysis of transient heat transfer has been carried out for the workpiece by the finite element method, while the boundary element method has been used for the die. [ABSTRACT FROM AUTHOR]

Describes simulations of impact forging processes. Uses the explicit time integration finite element method, which is based on direct time integration of equation of motion, to compute the deformation of the workpiece and the dies. Uses the program developed to simulate the copper blow test performed on a 350,000J counter-blow hammer. The calculated result reveals a good agreement in the final deformed configurations between the experiment and the explicit simulation. In order to compare this with the explicit method, the implicit time integration rigid-plastic finite element program considering the inertia effect is also applied to the copper blow test simulation. As a result of the copper blow test simulation using the explicit program and the implicit program, finds that the calculated results have good agreements in available plastic deformation energy, forging load and equivalent plastic strain distribution. Finally, applies the developed program to simulations of multi-blow forging processes. Presents three major findings from the multi-blow forging simulations: (1) the continuous analysis technique used for the multi-blow forging simulations works well; (2) the blow efficiency and the forging load generated by blow operations can be analysed efficiently and simulated results coincide with previous experimental and analytical ones; (3) the geometrical configuration of the workpiece is closely related to blow efficiency. [ABSTRACT FROM AUTHOR]

Applies an updated Lagrangian finite element analysis with automatic remeshing scheme to three-dimensional hot extrusion through landless square dies. The remeshing procedure is composed mainly with decision for remeshing, transfer of state variables and mesh generation. The procedure is carried out fully automatically. In the procedure, it is difficult to generate the mesh automatically, considering the physical characteristics. Accomplishes mesh generation by introducing the modular concept. The mesh generated by the modular concept has advantages, especially for three-dimensional problems, such as economic computational time and consideration of physical characteristics. Classes the profiles of orifice into two cases; and develops the orifice adaptive module for each case and then carries out numerical examples by using the orifice adaptive modules. [ABSTRACT FROM AUTHOR]

In metal forming, there are problems with recurrent geometric characteristics and without explicitly prescribed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. The present study deals with non-steady-state three-dimensional finite element analysis for helical extrusion of twisted clover and trocoidal gear sections through a curved die. A boundary-directed remeshing scheme based on the modular remeshing technique has been proposed to reduce the errors arising in mapping of variables between old and new mesh systems. The computed extrusion pressures in reaching the near steady-state loading stage are compared with the results of the experiments as well as the steady-state analysis. The three-dimensional deformed pattern involving warping at the extruded end due to torsional deformation mode is demonstrated. For twisted clover and trocoidal gear sections, the twisted angle of an extruded product is smaller than that of the die, and the simpler the shape of the sections, the larger the amount of the deviation. [ABSTRACT FROM AUTHOR]