Investigation of Surface Finish Effect on Fatigue Strength of Carbon and Low Alloy Steels

The subcommittees on Design Fatigue Curve (DFC) and Design Fatigue Curve 2 (DFC2) in Atomic Energy Research Committee of the Japan Welding Engineering Society (JWES) developed a new fatigue analysis method. A design fatigue curve by this method is established by applying factors on stress and cycles, which have been derived by statistical analysis, to the best-fit curve using tensile strength as a variable considering the mean stress correction called the Smith-Watson-Topper approach. For high cycle region, the variable amplitude effect of EN 13445 is employed. This fatigue analysis method was brought to the JSME Code Committee, and the JSME reviewed this method, and decided to incorporate it into the JSME Environmental Fatigue Evaluation Method with some modifications including the fatigue strength reduction factor for surface finish effect. This paper addresses surface finish effect on fatigue strength of carbon and low alloy steels. To perform further investigation for surface finish effect on fatigue strength of carbon and low alloy steels, the DFC3 Subcommittee was established with the support of a Japanese utility project. A series of fatigue tests for surface finish effect was performed for carbon and low alloy steels in the utility project, and the fatigue test data were evaluated by the DFC3 Subcommittee. In this paper, the series of fatigue tests are introduced and discussed. Finally, the validity for the fatigue strength reduction factor for surface finish effect developed by the JSME Committee has been confirmed based on the above fatigue tests.