Effects of Statical Strength and Deformability of Steels on Tensile Impact Fatigue Strengths

Abstract

The absorbed energy which determines the impact strength of a material depends on the magnitude of deformation and the deformability of the material. In an impact fatigue test, the phenomena of fatigue strength may differ for the low-cycle fatigue region (where the plastic deformation acts mainly) and for the high-cycle fatigue region (where the fatigue crack propagation acts mainly). In this research, tensile pulsating impact fatigue tests were carried out on the carbon steels whose deformabilities were changed by the carbon contents (0.28∼0.89%), the notch forms (the stress concentration factor α=1.05∼3.00), and the heat-treatment conditions. The results obtained can be summarized that the impact fatigue phenomena in low-cycle fatigue region show quasi-characteristics in unit impact test, and at high-cycle fatigue range they do not depend on unit impact characteristics. The rolled material has a lower notch sensitivity factor than the annealed material, which is different from the conventional fatigue phenomenon.