In order to study the effect of notch on its impact fatigue strength of mild steels, low-cycle impact fatigue tests were carried out on the specimens of 0.2% carbon steel having various circumferential notches under repeated impact tensile loads. The experimental results are summarized as follows:
(1) The impact low-cycle fatigue strength σ, in the case of notched specimens, is expressed by
where Nf is the life of rupture, T is the loading time and m*, n* and D* are material constants.
(2) The relations of m* and n* with the stress concentration factor α are given by
where m0, a and b are experimental constants.
(3) The fatigue notch factor β is related to the stress concentration factor α by
where c is an experimental constant.