Fatigue Property of High Strength Steel with Artificial Defects under Cyclic Torsion with a Shear Stress Ratio of 0.1

Abstract

In this paper, torsional fatigue tests of high strength spring steel were conducted for bar-shaped specimens with artificial small defects of various sizes at a stress ratio of R＝0.1. The shear fatigue limit decreased with the increase in defect size. The relationship between fatigue limit and the square root of the projected area of the defect was evaluated. The relationship was defined by El Haddad’s short crack correlation substituting an intrinsic defect size for an intrinsic crack depth. The relationship was characterized by the approximate formulation using the parameter; thus, the fatigue limit with a small defect can be accurately estimated by the parameter.