Predictions of Fatigue Crack Propagation Path and Life of High-Tension Steel in Residual Stress Fields

Abstract

A criterion was sought for predicting the path of a fatigue crack in HT80 steel propagating in residual stress fields. The problem was investigated with respect to two questions: (I) which was the dominant factor in determining the fatigue crack path, the cyclic components or the maximum values of stress intensity factors (SIFs), and (II) what kind of criteria, expressed in terms of the foregoing dominant SIF parameter, could be used for predicting the fatigue crack path? For the first question, it was indicated that the cyclic components of SIFs determined the crack path. For the second question, it was found that the crack path could be predicted by applying the Δσθ maximum criterion, which predicted that the crack propagated in the direction of the maximum range of circumferential stress component. Crack propagation lives for cracks curved due to the existence of a hole were calculated by applying the “U-(crack opening ratio) estimation” method based on the superposition principle proposed by the present authors. The predicted lives were in good agreement with the experimental results. © 1993, The Japan Society of Mechanical Engineers. All rights reserved.