Notch high-cycle fatigue behavior of 38MnVS medium-carbon forging steel
LIU Xiang-jiang1, CHEN Zhen2, HUI Wei-jun2
1. Central Research Institute, Baoshan Iron and Steel Co., Ltd., Shanghai 201999, China; 2. School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, China
Abstract：Many actual forging components contain inevitable geometrical discontinuities or machining notches which may cause local stress concentration and thus induce early fatigue failure when it is subjected to cyclic loading. Therefore,high notch fatigue properties are also required to forging steels. In order to explore the notch fatigue behavior of microalloyed medium carbon forging steels,the high-cycle fatigue behaviour of a commercially used medium-carbon forging steel 38MnVS under different stress concentration factors (Kt=1,2,4) was studies by using rotating bending fatigue testing. The results show that there are notable fatigue limits in the S-N curves for both the smooth and notch specimens of the as-forged tested steel. There are significant influences of Kt on the notch fatigue limit and fatigue notch sensitivity (qf). When Kt was increased from 1 to 2 and 4,the fatigue limit decreased by 48% and 67%,respectively,and the qf value was 0.93 and 0.68,respectively,which reveals that the as-forged tested steel has high fatigue notch sensitivity. It is found that fatigue limit is a power function of Kt with its coefficient equals to smooth fatigue limit based on the results of this study and those in the literature. Finally,a simple and efficient method of estimating the notch fatigue limit of ferritic-pearlitic medium-carbon forging steel under different Kt is proposed.
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2020, Vol. 55 
