Notch Effect in Low-Cycle Fatigue : 1st Report, Low-Cycle Fatigue Strength of 0.48% Carbon Steel under Constant Load Amplitude

Abstract

A prediction method of low-cycle fatigue strength has been developed whereby the number of cycles to initiate a crack can be estimated for a notched specimen from the characteristics of the hysteresis loops of unnotched specimens and a few fatigue data of unnotched or notched specimens. Good predictions were obtained for annealed 0.48% carbon steel notched specimens under completely reversed load. The prediction method can be applied to various materials, specimen shapes and loading modes. The plastic strain range Δε_p at notch root was computed by the finite element method and the Bauschinger effect was also taken into consideration. The method was compared with Langer's and the one based on Neuber's rule. Although it is difficult to predict by other methods that the number of cycles to crack initiation of notched specimens can be larger than that of unnotched specimens at high load level, the present method does not contradict this phenomenon.