A Suggested Procedure for Combined Mode I — Mode III Fracture Toughness Testing

Abstract

Abstract Mode I fracture toughness testing is well developed and standards exist for determining both Mode I critical stress intensity factors and J integrals. However, combined Mode I — Mode III testing is not so well developed and no standards exist. The aim of this paper is to suggest a testing procedure for studying mixed-mode crack initiation and growth under linear-elastic and elastic-plastic conditions. Suitably defined formulations of the stress intensity factor denoted Kic and Jiiic were used to characterize linear elastic fracture. Under elastic-plastic conditions, suitable versions of the J integral denoted Jic and Jiiic were used to characterize crack initiation and the slopes of the resolved J resistance curves to characterize crack growth. Effects caused by surface rubbing which operate at high values of the Mode III/Mode I ratio are recognized as a complication in interpreting the data.