EFFECT OF STRESS RATIO AND TENSILE RESIDUAL STRESS ON NEAR THRESHOLD FATIGUE CRACK GROWTH

Abstract

The effects of stress ratios on the fatigue crack growth in a high tensile residual stress field are examined. Specimens, made of 600 MPa class steel, are center-cracked type which contain longitudinal weld beads along the center of the plate. Fatigue crack growth rates and crack opening levels are measured at several stress ratios (-1 to 0.91). Under these test conditions, cracks fully open regardless of the value of stress ratio, and fatigue crack growth rates and threshold stress intensity factor ranges do not depend on the stress ratios.