Shigeki Abe

Modeling of Large-Strain Cyclic Plasticity for Accurate Springback Simulation

This paper describes a model of large-strain cyclic plasticity and its verification by some experiments of cyclic plasticity and biaxial stretching. The performance of this model in springback simulation is discussed by comparing the calculated results for S-rail forming with the experimental data on high strength steel sheet (HSS) of 980MPa-TS. The results of numerical simulations of the springback agree well with the corresponding experimental data, including the torsion-type springback appearing in S-rail forming.

A Determination Method of Intermediate Die Surface in Multi-Step Forging by Means of an Optimization Technique

In forging operations, an appropriate die-shape determination is of vital importance. This paper presents a new method for automatic determination of the intermediate die surface in multi-step forging based on an optimization technique. In the first stage of the process, using a unique design parameter which generates the shape lying between the pre-form and the final product, a preliminary die surface, which gives the lowest forging load within the design space, is determined. In the second stage, further detailed optimization by local search is performed around thus obtained solution at the first stage. Constraints for avoiding material defects such as folding and cracking during forging are considered. The validity of this method has been confirmed by applying it to the die design for an axisymmetric backward extrusion problem.