A computational study of the dynamic deformation and fracture in a coated material

The deformation and fracture of a coated material with a modified surface subjected to dynamic loading are studied. A mechanical boundary-value problem formulated in terms of plane strain is solved numerically by the finite-difference method. The mechanical responses of a steel substrate and a boride coating are described by models of elastic-plastic media exhibiting isotropic hardening and elastic-brittle fracture, respectively. The geometry of the interface between the coating and the substrate corresponds to that observed experimentally and is explicitly accounted for in the calculations. Numerical experiments are performed using different loading velocities applied to the coating surface. The coating fracture behavior is shown to be essentially dependent on the strain rate. At low dynamic compression rates, crack nucleation in the coating is found to occur solely in local areas experiencing bulk tension and to grow in the direction of load application, whereas mixed tension-compression fracture mechanism is involved at high compressive loading velocities, and cracking basically follows the direction of maximum tangential stresses.