A critical evaluation of cohesive zone models of dynamic fracture

Finite element calculations of dynamic fracture based on embedding cohesive surfaces in a continuum indicate that the predictions are sensitive to the cohesive law used. Simulations were performed on a square block in plane s train with an initial edge crack loaded at a constant rate of strain. Cohes ive laws that have an initial elastic response were observed to produce spo ntaneous branching at high velocity, but to modify the linear elastic prope r-ties of the body. As a consequence the cohesive surface spacing cannot be refined arbitrarily and becomes an important length scale in the simulatio ns. Cohesive laws that are initially rigid do not alter the linear elastic response of the body. However, crack branching behavior was not observed wh en such a cohesive relation was implemented using a regular finite element mesh.