Gigacycle fatigue of high strength steel 54SiCrV6

An attempt has been made to characterize gigacycle (10 10 cycles) fatigue behavior of high strength spring steel (54SiCrV6) wire by means of an ultrasonic frequency of 20 kHz fatigue test and analytical techniques. The fatigue strength of the steel wires in gigacycle cycles 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 10 6 and 10 10 cycles. This result is much different from conventional hypothesis. The differences between conventional hypothesis and test results are presented. The extension line of low-cycle fatigue strength can be used as fatigue strength of gigacycle in stead of horizontal asymptotic. Observations of the fracture section were made by using Scanning Electron Microscopy (SEM) and chemical analyses were made with special instruments. The fatigue rupture mechanism of gigacycle of high strength steel is discussed.