Numerical modelling of structural degradation under adiabatic shear banding and micro-voiding
Résumé
Adiabatic shear banding (ASB) is a strain localization phenomenon occurring in high strength materials like titanium and aluminium alloys subjected to dynamic loading involving quasi adiabaticity and low stress triaxiality conditions. Since it acts as a precursor to catastrophic failure, see e.g. Longère and Dragon [1], it is thus crucial to numerically model its formation and consequences when dealing with structures submitted to high loading rates. A large scale postulate is used herein to obtain a global insight into the structural material response. The adiabatic shear band cluster is indeed contained/embedded within the representative volume element (RVE), and not the opposite as usually considered. The effects of ASB initiation and evolution on the RVE (material point) response are double: kinematic, namely a progressive deviation of the plastic flow in the band plane, and material, namely a progressive anisotropic degradation of the elastic and plastic moduli. A physics-motivated, unified constitutive model has been initially developed in order to describe both aforementioned ASB effects, see Longère et al. [2], and then recently completed to reproduce the consequences of microvoiding in the band wake, see Longère and Dragon [3]. The enlarged model has been implemented as user material into the engineering finite element (FE) computation code LS-DYNA in the context of standard FE kinematic formulation. The performances of the numerical model are assessed regarding initial-boundary value problems with increasing complexity. [1] P. Longère and A. Dragon, 2015, Dynamic vs . quasi-static shear failure of high strength metallic alloys : Experimental issues, Mech. Mat., 80, pp.203–218. [2] P. Longère, A. Dragon, H. Trumel, T. De Rességuier, X. Deprince, E. Petitpas, 2003, Modelling adiabatic shear banding via damage mechanics approach, Arch. Mech., 55-1, pp.3–38. [3] P. Longere and A. Dragon, 2016, Enlarged finite strain modelling incorporating adiabatic shear banding and post-localization microvoiding as shear failure mechanisms, Int. J. Damage Mech., 25-8, pp.1142-1169.