Laser shock peening to improve the fatigue resistance of AA7050 components

Abstract

Purpose Laser shock peening (LSP) is a process capable of introducing compressive residual stresses into a metallic component. The residual compressive stress field can extend deeper below the treated surface than that produced by conventional shot peening (SP). The effect of such deep compressive stress profile is expected to result in a significantly greater benefit in fatigue resistance after LSP compared to SP. The purpose of this paper is to examine this further. Design/methodology/approach Residual stress profiles have been determined by X‐ray diffraction and incremental centre hole drilling. They have been correlated with the respective LSP process parameters and the obtained fatigue behavior. Findings A significant improvement of the fatigue life was found for an R ratio of 0.1. SP leads to a fatigue improvement of about 15 percent. For the same specimen geometry, a fatigue life improvement of about 25‐35 percent, depending on the load level, can be obtained after LSP. However, not only for the positive R ratio, where it is quite obvious, but also for the negative R ratios, R=−1 and −3, an increase of the fatigue life is generated by SP and LSP. Originality/value A shown LSP has a high potential for extending the service life of metallic components at the design stage, but it may also be possible to apply this technique to in‐service aircraft to extend the service goals of existing structures.