In modeling crack growth along an interface between a ductile material and an elastic material, or between two elastic-plastic materials, cohesive models have been a valuable tool for representing the evolution of failure in the process region just ahead of the crack tip. When ductile yielding occurs in the material surrounding the crack-tip this significantly increases the fracture toughness above the value corresponding to the work of separation per unit area in the crack plane. Here different cohesive models will be discussed. One follows the usual idea of a specified traction separation law on the interface, one modifies this approach by introducing a strain dependence, and the last approach uses special cohesive zone elements in which a damage model can be used to represent the fracture process zone. Due to mismatch of elastic properties across the interface the corresponding elastic solution has an oscillating stress singularity, that has to be accounted for if conditions of small scale yielding are used in analyzes.
展开▼
