Microstructural effects on shear instability and shear band spacing

A constitutive relation that accounts for the thermally activated dislocati on motion and microstructure interaction is used to study the stability of a homogeneous solution of equations governing the simple shearing deformati ons of a thermoviscoplastic body. An instability criterion and an upper bou nd for the growth rate of the infinitesimal deformations superimposed on th e homogeneous solution are derived. By adopting Wright and Ockendon's postu late, i.e., the wavelength of the dominant instability mode with the maximu m growth rate determines the minimum spacing between shear bands, the shear band spacing is computed. The effect of the initial dislocation density, t he nominal strain-rate, and parameters describing the initial thermal activ ation and the initial microstructure interaction on the shear band spacing are delineated. (C) 2000 Elsevier Science Ltd. All rights reserved.