Influence of the characteristics of the 3D FE mesh on the evolution of variables used to characterize the stress state

It is well-established that the ductile fracture in metallic materials is a highly stress state dependent physical process. Past research has focused on the development of numerical tools that describe the mechanisms of the ductile damage. In this framework, the computed damage distribution is affected by the accuracy in the description of the stress state history, aside from the choice of the damage model. Thus, the main objective of this work is to assess the influence of the discretization adopted in the gauge area of fracture-calibration specimens, in the evolution and distribution of the field variables generally used to describe the stress state: the stress triaxiality and the Lode parameter. The numerical analysis is performed with the in-house solver DD3IMP. The results show that the required mesh refinement changes particularly when plastic instabilities arise. Moreover, the stress state variables can present an heterogenous distribution at the integration point level, which is in general smoothed when analysing the results at the nodes.