Study of Circumferential Crack Propagation under Combined Tension and Torsion Loading at Elevated Temperature

Abstract

This paper describes the circmferential crack propagation in multiaxial low cycle fatigue loading. Push-pull, reversed torsion and combined push-pull and reversed torsion low cycle fatigue tests were carried out using circumferential notched specimens of type 304 stainless steel at 873K and crack propagation rates were measured by a D. C. potential method. Elastic-plastic finite element analysis was also carried out to evaluate the crack and notch opening displacements and to examine the effect of frictional between cracked faces on Mode III crack. The friction decreased the crack opening displacement and plastic zone size ahead of crack tip. Crack propagation rates in push-pull, reversed torsion and combined push-pull and reversed torsion tests were not correlated with J integral range ΔJE calculated by conventional method and which was discussed in relation to the friction between the fracture faces. The crack opening displacement taking account of the friction effect correlated crack propagation rates in all loading modes within a factor of four band.