Surface fatigue crack life and penetration behavior of stress concentration specimen

Abstract

Surface defects in the structural members are apt to be origins of fatigue crack growth, which may cause serious failure of the whole structure. Most structural bodies have a part where stress concentration exists, such as welded joints, corner parts, etc. The analysis on the crack growth and penetration from these defects may, therefore, be one of the most important subjects on the reliability of the LBB design. The authors have analysed the fatigue crack propagation from the surface defect on the stress concentration part. The crack growth behavior can be explained quantitatively using Newman-Raju equation and the stress partitioning method proposed by ASME Boiler and Pressure Vessel Code Section XI. The stress concentration has little effect on the crack growth rate after penetration. Using the K-value proposed by the authors, a particular crack growth behavior and a crack shape after the penetration can be estimated quantitatively.