Fatigue limit evaluation of blunt-notched specimen using Δk th value of small crack (1st report: Study on the determination of the initial crack size with annealed carbon steel when stress ratio is zero)

The fatigue limit of a blunt-notched specimen is dependent on the fatigue crack initiation limit σw1. σw1 is the propagating limit of the micro fatigue crack at notch root. However, before now no method for evaluating the σw1 based on fatigue crack properties had ever been proposed. In this paper, it is suggested that the initial crack size is dependent on the relationship between the application limit of the characteristic elastic field of the notch and the fatigue crack length measured from the notch root. It is also found that when the initial crack size is given, σw1 can be evaluated from the threshold stress intensity factor range ΔKth .