Intra-element versus inter-element crack propagation: the numerical extensometer approach

Numerical modeling of crack propagation is still a pressing issue in fracture mechanics. The finite element method and its variations are usually used for this purpose. One of the possibilities for modeling crack propagation is the well-known cohesive fracture mechanics. Generally, commercial finite element programs use a predefined cohesive zone, i.e., inter-element cracking modeling. Alternatively, this paper proposes a numerical strategy where the cohesive cracks can nucleate and propagate at any finite element, i.e., intra-element cracking modeling. The numerical results show a good agreement between both models when the cohesive zone is predefined. Moreover, when compared to a bending experiment on a tunnel lining segment where cracks can appear anywhere, the proposed model (the intra-element cohesive cracking model) presents good accuracy where different cracks nucleate and propagate.