Multiscale crack propagation and crack coalescence using the XFEM

Many materials contain micro cracks which influence the overall behaviour of the structure, especially in case of crack propagation and crack coalescence. To consider micro cracks efficiently, they are taken into account in a domain of interest, here around the crack fronts, by applying the multiscale projection method. To capture the physical properties of cracks accurately and to avoid remeshing during the crack propagation process, all cracks in the multi scale problem are modelled using the eXtended Finite Element Method (XFEM).
To allow for crack propagation of micro cracks as well as macro cracks, and to model crack coalescence of cracks from dint scales, propagation and coalescence of cracks is computed on the finer scale. Stable crack growth is achieved via an adjustment of the applied boundary conditions acting on the coarsest scale. Due to crack propagation, the respective crack fronts change their positions such that the fine scale domains move fully adaptive through the domain