Dynamic energy release rate evaluation of rapid crack propagation in discrete element analysis

A numerical procedure for estimating the critical dynamic energy release rate (GI Dc), based on experimental data is proposed. Ageneration phase simulation is conducted where fracture parameters can be determined using an experimentally measured crack propagation history (position of the crack tip as a function of time). The discrete element method is used to simulate the dynamic fracture by implementing a node release technique at the crack tip. The results are compared with analytical data on the dynamic propagation of a crack in a semi infinite plate. It reveals that the node release technique causes dynamic instabilities that can only be corrected by adding numerical damping on the edges of the crack or in the entire sample. On the other hand, the progressive node release technique, based on an elasto-damage zone model does not generate dynamic instabilities. It is shown that for a linear relaxation scheme and a damage zone length equal to themean radius of the discrete elements, results comparable to finite element or analytical methods are obtained in plate structure. The present model offers an alternative to the finite element method to simulate self-similar ormore complex crack growth. It also gives a first proper analysis of the evaluation of the critical dynamic energy release rate in a lattice-discrete model.