Notch Dependency of the Effect of Superimposed Stress of High Frequency on the Fatigue Strength

Abstract

Notched and unnotched specimens made of S45C carbon steel were tested under the composite stress which consists of fundamental rotating bending stress of relatively low frequency and superimposed stress of high frequency. The ratio of the frequency of the fundamental cyclic stress to that of the superimposed stress was selected to about 12 for all types of specimens. From the test results, discussion was made on the dependency of the fatigue strength under the composite stress on the type of specimen. It was concluded that when the super-imposed stress was small, the superimposed stress did not affect the fatigue life and such a range of the superimposed stress was decreased with the increase of the stress concentration factor of the notch, and the when the stress concentration factor of the notch was small, the endurance limit under the composite stress was reduced by the effect of the superimposed stress.