A rate-dependent cohesive continuum model for the study of crack dynamics

A rate-dependent cohesive continuum model is developed to represent material particles interacting in a viscous medium. Interactions between material particles are modeled using a cohesive force law while microstructural resistance to relaxation is represented by a phenomenological continuum viscosity function. The model exhibits two failure mechanisms, elastic bond breaking and viscous weakening, which combine to induce rate dependence in the cohesive strength, fracture energy, and cohesive state wave speed. The model is used to simulate dynamic crack propagation. Results display rate-dependent terminal speeds which correspond to the cohesive strength and not to the local driving force; thus supporting the local limiting speed hypothesis. (C) 2004 Elsevier B.V. All rights reserved.