Cyclic crack propagation at corners and holes

ABSTRACT Cracks frequently change their shape at geometric discontinuities such as corners or holes. Using the MTU automatic fatigue crack propagation software CRACKTRACER, this phenomenon is investigated for a simple specimen with square cross section and a drilling hole. The analysis shows that a change in crack shape takes place as soon as a discontinuity is reached and can be interpreted as being triggered by the resulting change of intersection angle with the free boundary. This leads to a violation of the previously existing equilibrium conditions and a sharp increase in the local stress intensity factors (K factors). Thereupon, the crack rapidly converges towards a new equilibrium configuration.