High-temperature fatigue crack propagation study of superalloy GH4169 by single-lens 3D digital image correlation

Abstract

The characterization of fatigue crack propagation behavior is crucial for performance and reliability evaluation of aerospace materials. In this study, high-temperature (maximum: 650°C) fatigue crack propagation experiments of Ni-based superalloy GH4169 were conducted. The bi-prism-based single-lens 3D digital image correlation (BSL 3D DIC) technique was used to in-situ measure the displacement and strain fields near fatigue crack tip. Based on the deformation information, the mode I stress intensity factor range ΔK and the crack opening displacement (COD) were determined for characterizing the crack closure effect. As the major fatigue crack growth model, the parameters of modified Paris’ law were obtained based on the effective stress intensity factor range ΔKeff and the fatigue crack propagation rate (FCPR). Additionally, two kinds of J integrals, JP (path integral method) and JK (stress intensity factor K method), were used to evaluate the small-scale yielding approximation.