Fatigue damage evolution of torsionally loaded aluminium alloy specimens; influence of shot peening

摘要

The evolution of fatigue damage due to torsion loading has been investigated in aluminium alloy specimens as functions of cycle number and depth below the specimen surface, respectively. The experimental techniques used were scanning electron microscopy, optical microscopy of plastic replicas, and fluorescent penetrant inspection. A number of shear-type deformation mechanisms were found: axial and circumferential cracks on un-peened specimens, axial cracks and circumferential slip bands, later evolving into cracks on shot peened specimens. In both cases, cracks were delineated by fretting debris formed by the rubbing action of the fracture facets. The deformation mechanisms found have been used in an attempt to rationalize the in-fluence of shot peening on the torsion fatigue properties which have been reported earlier by 2 of the authors.