A mechanism for the production of intrusions and extrusions during fatigue

Abstract

Abstract The outline of a model for intrusion and extrusion production has been devised which combines the recent calculations of dipole-dislocation strain field interactions with the observation that large numbers of dipoles are formed during low-stress fatigue. Large numbers of dipoles are produced near to and roughly parallel to the surface during one-half of the stress cycle. When the stress is reversed, these dipoles are pushed to the surface by dislocations moving outward from the crystal interior. If most of the dipoles are vacancy type, then an intrusion will be produced. If interstitial dipoles are more numerous, an extrusion will result. The model is a simple development of the mechanism proposed by Partridge.