Embedded crack model. Part II: combination with smeared cracks

The paper investigates the behaviour of finite elements with embedded displacement discontinuities that represent cracks. Examples of fracture simulations show that an incorrect separation of nodes due to a locally mispredicted crack direction leads to a severe stress locking, which produces spurious secondary cracking. As a possible remedy the paper advocates a new concept of a model with transition from a smeared to an embedded (discrete) crack. An additional improvement is achieved by reformulating the smeared part as non-local. Various criteria for placing the discontinuity are compared, and the optimal technique is identified. Remarkable insensitivity of the resulting model to mesh-induced directional bias is demonstrated. It is shown that the transition to an explicit description of a widely opening crack as a displacement discontinuity improves the behaviour of the combined model and remedies certain pathologies exhibited by regularized continuum models.