Experiments and numerical simulation of stress-state-dependent damage in sheet metal forming

Abstract

Experiments and corresponding numerical simulations with new biaxially loaded specimens taken from thin metal sheets are discussed. Inelastic deformations as well as damage and fracture behavior of the specimens are investigated under different biaxial loading conditions covering a wide range of stress states to analyze the stress-state-dependent damage and failure mechanisms in ductile metals. During the experiments strain fields in critical regions of the specimens are analyzed by digital image correlation. Corresponding numerical simulations deliver information on stress states in tested specimens. The results are used to propose stress-state-dependent damage and failure criteria corresponding to various damage mechanisms depending on stress triaxiality and the Lode parameter. They are validated by series of biaxial experiments with newly developed specimens and corresponding numerical simulations. This demonstrates the efficiency of the new specimens' geometries covering a wide range of stress states in the shear-tension and shear-compression regime allowing validation of stress-state-dependent functions for the damage criteria and damage evolution laws.