Abstract
In this study torsional fatigue test has been performed to investigate fatigue strength of notched specimen. There are two of notched specimen, i. e., type H is specimen with a drill hole, type P is specimen with a drill hole with chamfer by plastic deformation by press working. The main results obtained in this test are as follows; (1) The fatigue limit of type P is 1.6 times higher that of type H. (2) The work-hardening layer by plastic deformation suppress the crack growth rate at early stage. (3) The fatigue crack of type H initiates at edge of drill hole. On the other hands, that of type P initiates a little apart from the chamfer edge.
