A CONSTITUTIVE MODEL FOR THE DYNAMIC-RESPONSE OF BRITTLE MATERIALS

A microphysically based material model for the dynamic inelastic response of a brittle material is developed. The progressive loss of strength as well as the post-failure response of a granular material with friction are included. Crack instability conditions (an inelastic surface in stress space) and inelastic strains are obtained by considering the response of individual microcracks to an applied stress field. The assumptions of material isotropy and an exponential distribution for the crack radius are invoked to provide a tractable formulation. The constitutive model requires a minimal number of physical parameters, is compatible with a previously developed ductile fracture model [J. Appl. Phys. 64, 6699 (1988)] that utilizes inelastic surfaces, and can be formulated as an efficient, robust numerical algorithm for use in three-dimensional computer codes. The material model is implemented into a Lagrangian computer formulation for the demonstration of material response to dynamic loading conditions. Comparisons with one-dimensional, uniaxial impact experiments are provided.