ON THE ROLE OF STRAIN GRADIENTS IN ADIABATIC SHEAR BANDING

The effect of higher order strain gradients on adiabatic shear banding is investigated by considering the simple shearing of a heat conducti ng thermoviscoplastic material with a gradient-dependent flow stress. The competition between the gradient-dependent plastic flow and heat c onduction and their influence on the shear band width and structure ar e examined. Two internal length scales, i.e., the deformation internal length and the thermal internal length, are incorporated into the lin ear stability analysis, which shows that the band width size scales ei ther with the square root of the strain gradient coefficient (in the a bsence of heat conduction) or the thermal conductivity (in the absence of strain gradients), respectively. The numerical computation for the nonlinear problem reveals that the ''diffusive'' effect of the strain gradient is much stronger than that of the heat conduction and dictat es the constitutive response of the material in the postlocalization r egime, and shows that the deformation length scale is much larger than the termal length scale. The band width predicted by the gradient the ory agrees reasonably well with the experimental observations found in the literature.