SIMULATIONS OF DUCTILE FAILURE WITH 2 SIZE SCALES OF VOIDS
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abstract
Simulations of ductile failure in plane strain tension with a superposed hydrostatic stress are carried out for a material where failure involves two species of voids. The material is described in terms of an elastic-viscoplastic constitutive relation for ductile porous solids that accounts for ductile fracture by the nucleation and growth of voids. Two populations of initial inhomogeneities are represented, large inhomogeneities that are discrete initial voids or that have some initial porosity or that nucleate voids at an early stage, and small, uniformly distributed particles that require large strains before cavities nucleate. A doubly periodic array of clusters of the larger inhomogeneities is analyzed. Inhomogeneity distributions oriented orthogonal to the tensile axis and at 45 degrees to it are considered. When the larger inhomogeneities are represented in terms of increased initial porosity or in terms of an increase in void nucleation amplitude, the overall stress-strain response differs little from that of the background material until failure initiation, which is defined as the strain at which the stress carrying capacity drops abruptly. The large inhomogeneities have the dominant effect on failure initiation and the failure initiation strain varies little between the two orientations considered. When the larger inhomogeneities are discrete voids, porosity in the background material has a greater effect on the overall stress-strain response and the orientation dependence of the response is increased.
