High-Cycle Fatigue Properties and Damage Mechanism of Q345B Structural Steel

Abstract

The high-cycle fatigue behavior of Q345B structural steel was investigated experimentally. Highfrequency vibration fatigue testing machine and scanning electron microscopy were used to study the high-cycle fatigue S—N curve characteristics and crack initiation mechanism at ambient temperature. The surface temperature of the specimens was monitored. The relation between the fatigue limit and the amount of heat dissipation was also investigated. It was found that the fatigue life changed inversely with the stress amplitude in the high-cycle range. The fatigue limit in high cycle range was obtained from heat dissipation in the specimen and found to have good agreement with the S—N curve. The crack initiation was attributed to the surface defects and the persistent slip bands due to the cycle slip in fatigue loading.