We are pleased to introduce Prof. Jörn Mosler as our speaker as the speaker for this years christmas event. Prof. Mosler also started his career in Bochum, where he did not only do his diploma in civil engineering, but also his dissertation and habilitation.
Cohesive zone models represent a well-established and powerful framework for non-linear fracture mechanics. In contrast to classic bulk material models, they are based on traction-separation laws. As far as the finite element method is concerned, cohesive zone models are most often implemented by means of zero-thickness interface elements. However, since the geometry of the material interfaces such as that of cracks is usually not known beforehand but part of the solution, tracking of the involved interfaces becomes very challenging for zero-thickness interface elements. By way of contrast, phase field models do not show this problem. In this talk, a phase field approximation of cohesive zone models is discussed. Starting from the underlying sharp interface cohesive model, the phase field method for brittle fracture is first revisited. Particularly, it is shown that different mathematical solution concepts (e.g., local energy minima vs. global energy minima) may lead to different solutions – sometimes they even violate physics observations. Within the second part of the talk, the framework for brittle fracture is extended to cohesive zone models. In contrast to previous works, the three-dimensional phase field models is shown to converge to its underlying sharp interface model.