Influence of Femtosecond or Nanosecond LaserPeening on Plane Bending Fatigue Characteristics of Friction StirWeldingA2024 Joints

Abstract

In order to improve the fatigue properties of a similar butt friction stir welded joint of A2024 Aluminum alloy, two types of laser peening with femtosecond or nanosecond pulse laser equipment were applied. Fatigue tests were conducted at stress ratio R= -1, road frequency 23Hz with plane bending fatigue condition. Fatigue property was improved by both laser peening treatments and the fatigue strength at 10⁷ cycles of FSWed specimen was improved to the same level as that of the base metal for both treatments. Residual stress distribution, Vickers hardness distribution and surface roughness were measured and the relation between fatigue strength and these peening effects were investigated. As the results, it became clear that the residual stress was the most effective factor in improving the fatigue strength.