The geometry dependence of the JR curve for circumferential growth of through-wall cracks in cylindrical pipes subject to bending loads. II: Effect on the instability criterion

Proceeding from the experimentally vindicated basis that circumferential growth of a through-wall crack in a circular cylindrical Type 304 stainless steel pipe subject to bending loads is associated with a constant crack tip opening angle, an earlier paper has predicted the shape of the J_R curve in terms of geometrical and material parameters. The predictions compare favourably with experimental results for 4 in. (～ 10 cm.) diameter pipes containing circumferential through-wall cracks with different sizes. In this paper, the implications of the geometry dependence of the J_R curve are considered in relation to the criterion for the instability of circumferential crack growth. Limitations of the tearing modulus approach are accordingly highlighted, particularly if it is used for a material with a low crack growth resistance.