Det.-Criterion of Fracture

Abstract

Various criteria have been introduced for the determination of the conditions of initiation and the prediction of the propagation direction of a crack subjected to combined mode-I and mode-II in-plane deformations. First of all, Griffith [3] introduced a criterion based on physical consideration to determine the conditions to initiate the propagation of a crack. Erdogan and Sih [69] developed the maximum tangential stress criterion, according to which the crack will propagate along the direction of the maximum tangential stress. The maximum energy release rate criterion, the G-criterion [233, 234], represents a generalization of Griffith’s original energy release rate concept [3]. Sih [74] developed the minimum elastic strain energy density criterion (S-criterion) which is based directly on the total strain energy density, that is, the sum of its distortional and dilatational components. Theocaris and Papadopoulos [83] proposed the two-term approximation S2-criterion (Sect. 4.3) which is a modification of the usual S-criterion with a closer approximation, which considers two terms in the series expansion of the stress function [89], instead of only the singular term anticipated by Sih.