Effect of Grain Size on Low Cycle Fatigue in Low Carbon Steel

Abstract

Low cycle fatigue tests were performed on a low carbon steel of 0.1 percent carbon content, which has various grain sizes of the range from 18 to l63μm in diameter. The cyclic softening is followed by a stationary state in cyclic deformation behavior in the fine grain material, while the coarse grain one exhibits a rapid cyclic hardening in the early stage, which is followed by a saturation hardening. Such a difference in cyclic deformation property can be interpreted well by considering that in the yielding behavior between the fine and the coarse grain materials. The cyclic stress-strain property is not influenced, by the grain size. The coarse grain material of 163μm in diameter has about 0.4times shorter fatigue life than that in the fine grain one of 18μm. The grain size dependent fatigue life of this kind is valid for both processes of crack initiation and propagation.