The influence of the initial microdamage anisotropy on macrodamage mode during extremely fast thermomechanical processes.

In recently proposed thermo-elasto-viscoplastic material model for metals, the damage is described by the second-order tensor, called microdamage tensor to express the experimentally observed anisotropy (Perzyna in Mechanics 27(1):25-42, ; Glema et al. in Int J Damage Mech 18(3):205-231, ; Sumelka in The constitutive model of the anisotropy evolution for metals with microstructural defects. Publishing House of Poznan University of Technology, Poznań, ). This variable influences the entire deformation process being modelled, inducing anisotropic response of the material. In this model, the microdamage evolution is additively decomposed into the nucleation and the growth terms. However, for the sake of simplicity, for extremely fast thermomechanical processes, which are considered as a central point, microdamage nucleation term can be omitted. It induces the necessity of the initial anisotropic microdamage state definition in physically justified bounds (growth is possible only for nucleating or existing microdamages). This paper deals with the consequences of different initial microdamage anisotropy assumption, indicating its significant role in proper description of damage. In particular, we conclude that for detailed experimentally observed damage evolution mapped by the model (e.g. macrodamage initiation time, the velocity of macrodamage evolution, the geometry of macrodamage), its anisotropic description is necessary. [ABSTRACT FROM AUTHOR]