The effects of laser shock peening (LSP) on the fatigue life of AA7075-T651 were investigated. The combined influence of surface imperfections (i.e. pits and intermetallics), compressive residual stresses (CRS) and the applied stress on crack initiation sites (surface or subsurface) and the associated fatigue life were investigated. Critical surface imperfections were found to significantly reduce the benefits of LSP in life improvement, by promoting surface crack initiation despite the resisting effects of CRS. To facilitate quantifying the effects of LSP on fatigue life, a finite element (FE) model was developed to simulate residual stress distribution induced by LSP, as well as its redistribution caused by the formation of surface pits. Based on the FE results, a method identifying whether the specified surfaces pits and intermetallics are critical to lead to surface cracking at given stress conditions was proposed, based on the Smith-Watson-Topper method and the Murakami's model respectively. The interaction between surface imperfections, CRS and the applied loads were taken into account in this method. In addition, a fatigue life assessment framework was proposed based on the prediction of crack initiation sites, which was validated to be reliable in efficiently evaluating the efficacy of the applied LSP in improving fatigue life.
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FunderThis study is financially supported by the Engineering and Physical Sciences Research Council (EPSRC), UK (Grant EP/N509747/1). The authors would like to acknowledge the funding and support of the University of Southampton. The support of Coventry University for performing residual stress analysis and providing laser shock peening expertise. The Council of Scientific and Industrial Research (CSIR) of South Africa for access to laser shock peening equipment and expertise. The financial support and sponsorship by Airbus Operations GmbH. Michael E. Fitzpatrick is grateful for funding from the Lloyd’s Register Foundation, a charitable foundation helping protect life and property by supporting engineering-related education, public engagement, and the application of research.
- Compressive residual stress
- Crack initiation
- Laser shock peening
ASJC Scopus subject areas
- Modelling and Simulation
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering
- Industrial and Manufacturing Engineering