Influence of Thermodynamical Couplings on Adiabatic Shear Band Localization Failure

Abstract

The paper aims at the investigation of the influence of thermomechanical couplings on adiahatic shear band localization fracture. In technical dynamical processes fracture can occur as a result of an adiabatic shear band localization generally attributed to a plastic instability generated by thermal softening during plastic deformation.

The paper consists of three parts according to three main stages of the thermodynamic plastic flow process considered. The first part is devoted to the investigation of the influence of thermodynamical couplings on criteria for localization of plastic deformation along the shear band. The initial part of the thermodynamic plastic flow process is treated in quasi-static and adiabatic approximation. A thermo-elastic-plastic model of a material with internal micro-damage effects is used. A procedure has been developed which allows us to use the standard bifurcation method in the examination of the adiabatic shear band localization criteria. The influence of two important thermal effects, namely thermal expansion and thermal plastic softening on the criteria of localization of plastic deformation is investigated. Similar influence of spatial covariance terms is also examined. The second part of the paper brings an analysis of the influence of thermomechanical couplings on micro-damage mechanism. Post-critical behaviour within the shear band region is described by a thermo-elastic-viscoplastic model of a material with advanced micro-damage process. Both models, which describe pre- and post-critical responses of a material are developed within the thermodynamic framework of the rate type constitutive structure with internal state variables. Both these models are also consistent with the requirement that the elastic-plastic response of a porous solid can be obtained as a limit case for quasi-static processes of the elastic-viscoplastic behaviour. The third part examines the influence of thermomechanical couplings on final failure mechanism.