1974 年 23 巻 244 号 p. 64-68
In order to clarify the mechanism of fatigue crack propagation, the plastically deformed zones at the crack tips were measured by means of two microbeam X-ray diffraction techniques: The transmission Laue method and the back reflection Debye-Scherrer method. The material used was annealed, extremely pure aluminum of 99.999%, and the specimens were subjected to cyclic tension and compression loads. The distribution of maximum shear stress, τmax, around the crack tip was estimated by Sneddon's formula. It was found that the plastically deformed zones appear in accord with the τmax distribution; that is, the minimum deformed region exists at the front of the crack tip and the maximum one appears in the direction 40°∼50° off from the crack propagating direction. I was also clarified that the total misorientation of the grain near the crack tip inside of the specimen is slightly larger than that on the surface.