Ductile Fracture.

Modeling and computational tools were developed to carry out analyses of dynamic ductile fracture and brittle-ductile transitions without using any ad hoc crack growth criteria. Among the key results obtained were 1 prediction of a non-monotonic size effect in dynamic ductile failure processes, 2 resolution of an apparent paradox where under certain loading conditions steels, and other materials, exhibit brittle failure at low loading rates and ductile failure at high loading rates and 3 three dimensional simulations of dynamic crack growth that, for the first time, illustrate shear lip formation and relate what is seen on the surface with what is happening in the interior, which is generally inaccessible in an experiment. Analyses of deformation and failure in metal matrix composites revealed that the development of hydrostatic tension fields arising from constrained plastic flow play a key role in determining the deformation and failure behavior of these materials. Detailed comparisons with experiment showed that our analyses provide remarkably accurate predictions of composite behavior and rationalize experimentally observed trends, such as the relative insensitivity of composite yield strength to changes in matrix microstructure and the dependence of ductility on the morphology and distribution of the reinforcement.