Abstract
In order to clarify the effect of strength level on the fatigue prorerty in a wide life region, fatigue tests in the life region of N=0.5∿(10)^9 were performed for high strength steels of SUJ2,SUCM439 and the carbon steel of S35C with low strength. S-N characteristics of respective steels were compared with each other and the fatigue mechanisms were discussed from a view point of fractography. Thus, it was found that S-N property for high strength steels of SUJ2 and SNCM439 have duplex S-N characteristics, respectively. However, the S-N property for the low strength steel of S35C does not have such an aspect, but it has the simple S-N characteristics.
