On the autonomy of the process region

Abstract

An investigation of the autonomy of the process region at the tip of a crack is carried out. An elastic plastic linearly hardening material is assumed. A cohesive zone model with constant cohesive stress is chosen. The cohesive zone length is observed to decrease with decreasing hardening rates and increasing cohesive stresses. For a cohesive stress larger than about three times the yield stress the zone becomes extremely small for hardening rates relevant for e.g. structural steels, and for perfectly plastic materials it did not develop at all. The autonomy of the cohesive zone was found to extend to at least 1.65 times the load specified for linear fracture mechanics. A very accurate description of the state of the process region is given by the near region J-integral. Only a slight improvement is obtained by using the J-integral taken for a path outside the inelastic region instead of using the stress intensity factor.