疲労限度の結晶粒径依存性に及ぼす予ひずみの影響 : 純鉄材の回転曲げ

抄録

In order to clarify the effect of grain size on the fatigue limit of pure iron, the effects of prestrain on the relation between the fatigue limit and grain size are investigated through rotating bending tests in the range of 0∼20% prestrain. It is found that the fatigue limit of prestrained as well as annealed material depends on grain size, and the dependence is not affected by the amount of prestrain. Yield stress gradually becomes independent of grain size with an increase in the prestrain. Therefore, it is concluded that the mechanical properties of the material which are influenced by grain size, i. e. yield stress, hardness and so on, are not the major factor in the grain-size dependence of the fatigue limit in both the annealed and prestrained materials. It is also found that the crack initiation stress increases as the prestrain increases, and remains dependent on grain size, while the slip initiation stress is increased little by the prestrain and has a small grain-size dependence.