The heuristic considerations, which are responsible for the orientation of the fictitious cracks in the classical models, are replaced by an analytically de- rived expression. The critical directions of the failure planes are shown to depend solely on the character…
The heuristic considerations, which are responsible for the orientation of the fictitious cracks in the classical models, are replaced by an analytically de- rived expression. The critical directions of the failure planes are shown to depend solely on the character of the unilateral fracture criterion and on the applied loading. The ductility of the material is found to play a key role in the process of secondary cracking. Based on these findings, the range of applica- bility of the classical formulations is assessed. The analytical model also al- lows for the derivation of a homogenized 'equivalent macroscopic failure criterion', which can be related directly to Griffith's criterion of fracture me- chanics.