A 2D Lode improved Lemaitre's ductile damage model for damage prediction in ductile sheet metals under various loading conditions

Abstract

Accurate prediction of ductile damage is a critical challenge for the safe design of sheet metal structures. The Lemaitre's ductile damage model has been widely used for prediction of ductile damage, however its accuracy fully depends on loading conditions and calibration range. This paper eliminates this limitation by proposing a 2D Lode improved model (LIM) of the original Lemaitre (OL) for sheet metals. The modification incorporates the Lode parameter, a crucial, often-neglected factor influencing damage evolution. First, the LIM's theoretical framework and constitutive equations for the plane stress conditions in sheet metals including the Lode parameter is completely presented. Then, numerical approaches such as counting search and Taguchi methods are employed and validated for identification of the model parameters. Finally, to evaluate the LIM's performance, a user-defined VUMAT subroutine is developed for numerically simulation of numerous specimens under diverse loading conditions as well as to assess the model's effectiveness and reliability. The numerical simulation results are compared with experimental data and the comparison demonstrates a significant improvement in accuracy of the LIM rather than the OL ductile damage model. © 2024 Elsevier Ltd