Abstract
Commercial base pure iron plate specimens were testes under reversed and pulsating axial stress in a high cycle fatigue range, and the crack nucleation sites and the subsequent growth pass of cracks were analyzed in terms of the crystallographic orientation of grains surrounding the cracks. It was observed that fatigue cracks nucleated at grain boundaries satifying some crystallographic configurations under completely reversed stress, but the crack nucleation sites were along persistent slip bands inside the grains under pulsating stress. the crack growth toward the inside from the surface was observed to take place in the shear mode along dominant slip systems in the same manner as the pencil glides, irrespective of the stress patterns.
