INTERACTIVE EFFECT OF 2 COPLANAR CRACKS ON PLASTIC YIELDING AND COALESCENCE

A theoretical study of the conditions for coalescence of two fatigue c racks in a multi-crack system is presented. As both cracks grow, the n ear-side plastic zone sizes of the interacting cracks increase more ra pidly than the off-side zone sizes which results in higher overall cra ck propagation rates for an interacting crack growth system than the s imple addition of individual crack growth rates. The use of a single c rack growth model to predict failure in the presence of two or more cr acks may therefore underestimate the interaction between cracks and le ad to un-conservative predictions. Some of the theoretical predictions were confirmed by published results of experimental measurements of c rack interaction distances in multi-crack systems.