An incremental stress state dependent damage model for ductile failure prediction

The goal of this contribution is to formally present an incremental damage model conceived to predict failure of ductile materials in forming and crash applications. Denoted henceforth by the acronym Generalized Incremental Stress State Dependent Damage Model (GISSMO), the present model's framework is based on an incremental damage accumulation which is dependent on a failure curve which, in turn, is a function of the current stress state. The damage variable is of scalar nature and inherently takes into account the effects of non-proportional loadings. Furthermore, GISSMO includes the evolution of an instability measure based on a critical strain. When this variable reaches unity, the coupling between the stress tensor and the damage variable is considered. This allows capturing the effects in post-critical regime macroscopically, from strain localization to final element erosion and crack formation. Since spurious mesh dependence is a concern when simulating material behavior up to fracture, a regularization strategy is proposed to compensate for the effects of mesh dependence in a global fashion. The aforementioned aspects of GISSMO are presented and discussed in detail in the present contribution as well as the calibration of the model based on experimental data of a dual-phase steel. It is shown that GISSMO is able to reproduce the fracture behavior of the calibrated material for several load paths.