Dislocation structures around the tips of propagating fatigue cracks in copper

Abstract
Dislocation structures in the immediate vicinity of a fatigue crack tip in Cu have been observed through an electron microscope operating at 2000 kV. It was found that most of the cells formed very near the tip are elongated in radial directions and that ladder-like structures can be developed in the interior as well as in the surface layer of fatigue specimens. The cyclic plastic zone predicted by theories of fracture does not seem to exist in the form of a specific metallurgical structure.