The effect of laser shock peening induced residual stress fields on fatigue crack growth in aluminium alloys
Abstract
Laser shock peening (LSP) has emerged as a potential technique to enhance the fatigue life of safety critical structures. LSP induces a compressive residual stress field through plastic deformation near material s surface. This compressive residual stress field counteracts applied tensile stress and increases the fatigue life of the component. The majority of research has concentrated on treating standard test coupons of simple geometry with little work focused on application of LSP to test coupons representative of the complicated shaped elements found in aircraft structures. Prediction of the fatigue crack growth behavior through geometries of complicated shape is difficult due to the complex stress field across the crack front, which is only accentuated by the non-uniform residual stress fields typically introduced via LSP. This project will develop a modelling method to predict fatigue crack propagation in components of complicated shape treated with LSP, and to validate these predictions with experimentation. Also, peening can modify the microstructure of the material near the surface especially if the peening was applied without a sacrificial coating. The modified microstructure has the potential to affect the fatigue crack growth behavior compared to the baseline material and will be studied in this project. The vast majority of published work in laser shock peening consists of constant amplitude loading tests. However, the combination of variable amplitude cumulative damage with the residual stress fields has the potential to significantly increase prediction complexity. The position of the crack tip within the residual stress field at a given time during the load spectrum must be predicted precisely otherwise small prediction errors could potential accumulate into much greater error in the final total life prediction.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 19, 2018
- Source ID
- FA95501817012
Entities
People
- Niall Smyth
Organizations
- Air Force Office of Scientific Research
- Coventry University
- United States Air Force