Gigacycle fatigue of high strength steel 65Mn

A study has been made to characterize gigacycle(1010 cycles) fatigue behavior of high strength spring steel(65Mn) wire by means of an ultrasonic frequency of 20kHz fatigue test and analytical techniques.The fatigue strength of the three-group steel wires with different properties for Gigacycle was determined at a load ratio R=-1.The experimental results show that fatigue rupture can occur and the fatigue endurance stress continues to decrease with increasing number of cycles between 106 and 1010 cycles,This result is much different from conventional hypothesis.The difference between conventional hypothesis and test results is proved.Observations of fracture section were made by using Scanning Electron Microscopy(SEM).The relation between the fatigue crack and cycles is found.The fatigue rupture mechanism of gigacycle of high strength steel 65Mn is discussed.The research is useful for the designer of ships and constitutor of ship standards.