A framework for modeling crack growth is described that is based on in
troducing one or more cohesive surfaces into a continuum. Constitutive
relations are specified independently for the material and for the co
hesive surfaces. Fracture emerges as a natural outcome of the deformat
ion process, without introducing an additional failure criterion. The
characterization of the mechanical response of a cohesive surface invo
lves both an interfacial strength and the work of separation per unit
area, which introduces a characteristic length into the formulation. F
inite element analyses are carried out for a plane strain block with a
n initial central crack, subject to impact loading. The crack is const
rained to grow along the initial crack line. Numerical results are pre
sented for elastic and elastic-viscoplastic solids using various degre
es of mesh refinement.