A new general finite element method for predicting shearing and piercing

Abstract

In this paper, a new general finite element (FE) method for predicting shearing, blanking, and piercing of ductile or forgeable metals is presented, emphasizing usability and conformality of the target shear-separated material in the context of automatic multi-stage metal forming. The approach is based on an element deletion/splitting element degradation model and sheared surface quality control; the former ensures the generality of the approach, whereas the latter aims to promote usability of the sheared or blanked material. The proposed approach is compatible with the traditional theory of ductile fracture, and material separation can be verified experimentally. The combined sheared surface quality control and element degradation model is applied at the precise time that material separation takes place. In the sheared surface quality control scheme, free nodes that should disappear after shearing/piercing instead move to positions nearest the fractured surface for conformality of the FE mesh. The shearing simulation is finalized by remeshing, followed by the application of a "free node algorithm" for surface quality control. This new method overcomes the numerical issues that can arise after deleting the severely damaged elements or split edges observed with conventional methods. The proposed scheme was used to simulate a three-dimensional round-bar shearing process for the production of short billets. The simulation and experimental results were compared. The results showed that our approach can easily, systematically, and precisely simulate metal forming processes involving finely sheared or blanked materials under a compressive stress state.