THE STEADILY PROPAGATING VISCOPLASTIC CRACK WITH ELASTIC UNLOADING

We analyze the crack-tip near field for a crack propagating under stea dy-state, quasi-static, antiplane strain conditions in a viscoplastic material. The constitutive model employed is a state variable model du e to Robinson, which displays kinematic hardening characteristics, and which allows for the possibility of elastic unloading. Given a contin uity assumption on the state variable components across the loading/un loading boundary, we find that the crack-tip near field is completely uninfluenced by conditions in the remote field. This conclusion is in agreement with earlier analyses in which the possibility of an elastic unloading zone was not admitted.