Crack Paths at Multiple-crack Systems in Anisotropic Simulation and Experiment

This paper is targeted on numerical methods for accurate crack tip loading analysis and crack path prediction. Those are based on finite element calculations of the boundary value problem. Applying path-independent integrals to curved cracks in order to accurately calculate the J-integral, energy release rate (ERR) or stress intensity factors (SIF) is still not state of the art. Contours which are not confined to the crack tip require special analytical preparation and numerical treatment to supply results which are sufficiently precise for reliable crack path prediction. Methods to improve the calculation of the J-integral and the interaction integral (I-integral) are presented. In particular, the latter has never been applied to strongly curved cracks. Also, efficient methods for the loading analysis and crack growth simulation of multiple interacting cracks based on path-independent integrals are presented. The anisotropy of fracture toughness is taken into account being a crucial part of the numerical model. Experiments are carried out with specimens made of aluminum alloy Al-7075, comparing subcritically grown cracks with simulations.