Presentation of an enhanced Lemaitre's ductile damage model for sheet metals

Abstract

To improve the accuracy of the original Lemaitre's ductile damage model under various loading conditions, this study proposes an enhanced version of the model for sheet metal forming processes under plane stress assumptions by incorporating a functional material-dependent damage parameter. For this aim, the theoretical framework, constitutive equations, and a robust numerical explicit algorithm for the new model are first derived. Subsequently, a comprehensive calibration process is widely performed using a varying number of calibration points to optimize the functional ductile damage parameter. In the following, a user-defined subroutine is developed to numerically simulate the damage behavior of several SS304 stainless steel specimens subjected to different loading conditions, including the Erichsen's forming test. The accuracy of the novel criterion is thoroughly investigated and fully validated by the corresponding empirical observations. Finally, the numerically predicted fracture locus and forming limit diagram of the material are compared with the relevant practical data. The comparison strongly highlights the improved predictive capability and reliability of the enhanced model. © 2025