Abstract
Fatigue crack growth test of a grain-oriented 3% silicon iron was carried out under constant amplitude loading. Shape of a specimen surface around the fatigue crack tip was transferred to thin plastic films, and these replica films were observed by means of an Atomic Force Microscope (AFM) with high resolution. In the high K region, two preferential slip systems operated in the vicinity of the crack tip. Slip behavior around the crack tip was observed at the maximum and minimum loads for several loading cycles, and slip deformation during loading or unloading cycles was evaluated quantitatively. By considering the slip deformation and intervals of two adjacent slips, it is found that the fatigue crack grows by two preferential slip systems operating alternately. The crack propagation was occurred by the slip deformation and the crack path was inclined because two slips operated asymmetrically.
