In situ through-thickness analysis of crack tip fields with synchrotron X-ray diffraction

Abstract

In this work a novel approach to estimate in situ the stress intensity factor (SIF) through the thickness of metal specimens is presented. It is based on a hybrid methodology that combines powerful synchrotron X-ray diffraction data with an elastic analytical model describing the strain field around the crack tip. A sensitivity analysis is conducted to understand the largest sources of error and their impact on the estimated SIF values. The accuracy in locating the crack tip position was found to affect the quality of the SIF estimation. Accordingly a procedure is developed to help locate the crack tip position. The methodology is tested on ultra-fine grained aluminium alloy 5091 and on a bainitic steel. It is recommended that an area of interest having a size at least 3 times larger than the plane strain plastic zone is mapped, providing good SIF estimations (within 8%) for all cases studied.