Effect of Notch on Impact Fatigue Strength of Mild Steels

Abstract

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
σN_f^m*T^n*=D^*
where N_f 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
m^*=m₀α^a, n^*=m₀α^b
where m₀, a and b are experimental constants.
(3) The fatigue notch factor β is related to the stress concentration factor α by
β=α^-cexpm₀(α^a-1)lnN_f
where c is an experimental constant.