Effect of Element Types on Failure Prediction Using a Stress-Based Forming Limit Curve

Abstract

Strain-based forming limit diagrams (FLDs) are the traditional tool used to characterize the formability of materials for sheet metal forming processes. However, this failure criterion exhibits a significant strain path dependence. Alternatively, stress-based FLDs have been proposed and shown to be less sensitive to the deformation path. The stress-based failure criterion can be conveniently implemented in numerical simulations. However, for reliable numerical modeling, the sensitivity of the models to the selection of discretization parameters, in particular, the element type must be assessed. In this paper, Marciniak tests have been numerically simulated to investigate failure prediction using three different element types (shell, solid, and solid-shell). Seven different specimen geometries were modeled in order to vary the loading paths. The results show that despite differences in stress calculation assumptions, shell, solid, and solid-shell elements do not provide differences in failure prediction when a stress-based failure criterion is used.