SIMULATION OF DYNAMIC FRACTURE OF AN IMPACT-LOADED BRITTLE SOLID

A new model for simulating dynamic fracture in impact-loaded solids is presented. This model is based upon the traditional molecular dynamic s procedure, but accounts for the irreversible nature of the fracture process by deleting the attractive part of the particle interaction po tential when the bond between two particles is stretched beyond a crit ical length. This critical length is determined by comparison with Gri ffith theory. In the present paper, the model is applied to a two-dime nsional homogeneous solid in the absence of microstructure (microstruc tural effects are treated in a subsequent publication). When the impac t zone is much smaller than the size of the sample, or the impact zone is wide and the impact amplitude is large, the first crack forms a fi nite distance ahead of the impact zone. Static continuum elasticity th eory shows that the position of this first crack occurs at the positio n of the maximum tensile stress. This crack then propagates back to th e edges of the impact zone and forward into the sample, thereby creati ng an X-shaped crack pattern. The tips of the X-shaped crack propagate more slowly than the stress wave and hence strong deviations from thi s pattern are observed when the stress wave passes the crack tips. Whe n 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 fro m the back surface.