Failure Mechanism of Very High Cycle Fatigue for High Strength Steels

In recent years, the core engineering components of high-speed train, automobiles and aircrafts are required to endure fatigue loads up from 108 to 1010 cycles. The present study results show that in the very high cycle fatigue (VHCF) regimes of more than 107 cycles, the fatigue failure of high strength steel materials can occur below the traditional fatigue limit, hence the VHCF investigations of high strength steels not only help to further understand the fatigue essence and mechanism, but also do research on the fatigue design and life assessment method. This paper summarizes works of VHCF researches for high strength steels in recent years, such as the characteristics of S-N curve, the observations on fish-eye, which is one of the typical characteristics of fracture surface, crack initiation, crack propagation, etc. The present work also analyzes the fatigue mechanisms and briefly discusses several factors that affect VHCF properties, such as hydrogen effect, inclusion effect, frequency effect. Some possible and prospective aspects of future researches are also proposed.