Showing papers by "Shiro Kobayashi published in 1991"

Three-dimensional analysis and computer simulation of shape rolling by the finite and slab element method

Abstract: In this study a new simplified 3-D numerical method and the associated computer program have been developed to simulate the shape rolling process. The 2-D rigid-plastic finite element method (FEM), used for the generalized plane-strain condition, is combined with the slab method. This method, called FSEM (finite and slab element method), reduces the computational effort without losing much accuracy obtained in the 3-D computer simulation of the shape rolling process. The FSEM has been used to develop a computer program, called TASKS for three-dimensional analysis of shape-rolling as a kinematically steady-state process. The program TASKS has been used to simulate the metal flow and the bulge profile in flat rolling of slabs, the shape rolling of a simple H section, and the rolling of a practical H-beam section. In flat rolling, predicted spreads agreed well with experimental results, given in the literature. The metal flow in rolling of a simple H section was compared with results of a full 3-D simulation, obtained by other investigators. The comparison indicated that the present predictions give quite good results. Finally, the predictions made for a practical pass, used in rolling H sections, also compared well with experimental data.

Preform design in ring rolling processes by the three-dimensional finite element method

Abstract: Perform design by the three-dimensional finite element method has been carried out for plain ring rolling and T-section profiled ring rolling. The application of the backward tracing scheme for perform design in ring rolling processes demonstrates, for the first time, the extension of the scheme into three dimensions. The preform design in plain ring rolling aims at obtaining a preform which simulates a final plain ring product with uniform axial height. Loading simulations were carried out for two progressively modified preforms derived from the result of loading simulations with a rectangular-shaped ring. Then, backward tracing was applied to obtain a final preform for the specified product configuration of uniform axial height. The preform in the T-section profiled ring rolling process was to be designed to simulate a final profiled ring product with complete filling in the groove and uniform axial height. The final preform shape for plain ring rolling was selected as a trial preform in T-section profiled ring rolling. A more satisfactory preform was obtained from the backward tracing results. It was shown by forward simulation that the final preform was good enough to satisfy the design criteria.

Application of the finite element method to powdered metal compaction processes

Abstract: A plasticity theory is summarized for a powdered metal compact. The constitutive equation is applied to the variational principle and its discretization is developed. The discretized formulation has been implemented into the finite element code and the program has been tested and applied to simulations of axisymmetric die pressings with copper powders. The simulation includes single-action and double-action pressings of solid cylinders as well as cylindrical rings. Predictions are made for density distributions, mean stress distributions, load-stroke relationships, average density as function of height, average density as function of radius, pressure distributions along die-walls and punches, and force fraction transmitted to the stationary punch. Some of the predicted solutions are compared with experimental observations from the literature. It was found that the results from the finite element analysis, in general, agree very well with the experimental observations.