Shear instability direction at a crack-tip in a thermoviscoplastic body

Deformation fields near a crack tip are analyzed for a thermoviscoplastic body deformed either in an antiplane shear or in plane strain. The effects of inertia forces and heat conduction are considered, but those of material elasticity are neglected. By assuming that a shear band initiating from the crack-tip propagates in the direction of the maximum effective stress. It is found that a shear band propagates along the crack ligament in the body deformed in an antiplane shear. For a body undergoing plane strain deformations, the direction of the propagation of the shear band depends upon the mode-mixity parameter and agrees with that observed by Kalthoff.