Some Issues in Cohesive Surface Modeling

A cohesive surface theory of fracture is a phenomenological continuum framework that is closely related to classical fracture mechanics. As such it shares the advantages and disadvantages of any phenomenological continuum frame- work. The continuum is characterized by two constitutive relations: (1) a volumetric constitutive law that relates stress and strain; and (2) a traction versus displacement jump relation across a specified set of cohesive surfaces. The cohesive traction can decrease to zero thereby creating new free surface. The cohesive surface formulation stems from the pio- neering contributions of Barenblatt and Dugdale and provides a means of addressing a variety of issues that are difficult, if not impossible, to address within a conventional fracture mechanics framework. A wide range of phenomena have been analyzed using a cohesive surface framework under both quasi-static and dynamic loading conditions, including for example micro cracking, debonding and void nucleation, fracture in complex microstructures, crack branching and fragmentation. No attempt is made to provide a balanced overview of that literature. Rather, the focus is on issues that have been of interest to me. Various analyses are discussed with attention on capabilities and limitations as well as on opportunities for extending the predictive capability of cohesive analyses of fracture and failure.