Crack initiation in polycrystalline aluminium fatigued at low strain

Abstract

The Nomarski optical interference contrast technique, together with electron microscopy, has been used to study crack initiation in polycrystalline aluminium fatigued at low strain. Cracks have been seen to develop along a new form of deformation marking as well as in persistent slip bands. This marking takes the form of surface undulations (rumples) arranged in a very regular manner. At no time have intense slip bands been detected associated with the rumples and it therefore appears that cracks can be initiated in regions other than persistent slip bands.