On dynamic FE analysis of viscoplastic thin-walled structures with anisotropic gradient damage

In this study an anisotropic gradient-damage model for dynamic finite element computation is established and validated by using the global displacement-force curves obtained from shock-tube tests on copper plate specimens. The model is formulated by introducing a gradient-enhanced free energy, which is enhanced phenomenologically in terms of an equivalent non-local damage variable and its gradient on the mid-surface of shell structures. This enhancement gives rise to an introduction of gradient parameters in terms of a substructure-related intrinsic length-scale and a relationship between non-local and local damage variable. Viscoplastic laws by Velde et al. 2010 are used with a modification of damage evolution law which is assumed to depend on the trace of the damage tensor, the tensile equivalent plastic strain and the norm of the principal strain tensor. The performance of the proposed model is demonstrated through preliminary numerical results, which are compared with results obtained by using existing local and non-local isotropic damage models.