Methodology for Evaluation of Residual Stress Effect on Small Corner-Crack Initiation and Growth.

The growth behavior of a naturally initiated corner crack under a uniform residual stress field is investigated in this study. A convenient method is proposed to induce and evaluate the uniform residual stress field for a beam-type specimen. Fatigue tests are conducted with a rotary bending fatigue machine to investigate the growth of the corner crack. For this reason, a cylindrical specimen, which is typically used for rotating bending tests, is modified into a beam specimen. The corner crack growth behavior under residual stress is evaluated based on linear elastic fracture mechanics (LEFM) and compared with long through crack data. The test results verify that the corner crack growth under residual stress can be effectively evaluated by LEFM and estimated using long crack data.