Measurement of mode II threshold stress intensity factor range ΔKIIth

Abstract

In order to measure the Mode II fatigue crack growth resistance of various materials, a particular chevron notched double-cantilever type specimen with side grooves was designed. Mode II fatigue crack growth tests by using the newly designed specimens were conducted by a conventional closed-loop type tension-compression fatigue testing machine under a constant load amplitude which corresponds to the ΔKII-decreasing test with increase in crack length. The crack length was measured by the AC potential method. The particular morphology of Mode II crack fracture surface was investigated. The distribution of shear stress in crack tip and Mode II stress intensity factor were analyzed using a FEM software, ABAQUS. The relationships between Mode II crack growth rate (da/dN) and ΔKII for various materials were obtained, and the values of ΔKIIth were determined. It was found that ΔKIIth is larger than ΔKIIth for all materials tested in this study.