Numerical prediction of the propagation of branched fatigue cracks

Abstract

A specialized finite element (FE) program is used to predict the propagation behavior of asymmetrically bifurcated cracks, which can cause crack growth retardation and arrest. The branched crack propagation path and associated stress intensity factors (SIF) are obtained for several bifurcation angles. It is found that very small differences between the branch lengths are enough to cause the shorter one to eventually arrest due to shielding effects. The SIF of the longer crack branch is also reduced due to the deflections, but it returns to the original non-bifurcated value as the crack propagates away from the influence of the (arrested) shorter branch. It is verified that crack bifurcation may provide an alternate mechanistic explanation for overload-induced crack retardation.