Simulation of dynamic fracture of an impact-loaded brittle solid

Abstract

A new model for simulating dynamic fracture in impact-loaded solids is presented. This model is based upon the traditional molecular dynamics procedure, but accounts for the irreversible nature of the fracture process by deleting the attractive part of the particle interaction potential when the bond between two particles is stretched beyond a critical length. This critical length is determined by comparison with Griffith theory. In the present paper, the model is applied to a two-dimensional homogeneous solid in the absence of microstructure (microstructural effects are treated in a subsequent publication). When the impact zone is much smaller man the size of the sample, or the impact zone is wide and the impact amplitude is large, the first crack forms a finite distance ahead of the impact zone. Static continuum elasticity theory shows that the position of this first crack occurs at the position of the maximum tensile stress. This crack then propagates back to the edges of the impact zone and forward into the sample, thereby creating an X-shaped crack pattern. The tips of the X-shaped crack propagate more slowly than the stress wave and hence strong deviations from this pattern are observed when the stress wave passes the crack tips. When the predominantly compressive stress wave reflects off the back free surface, a tensile wave propagates back into the sample creating even more damage. This damage occurs in bands parallel to and set back from the back surface.