A computational methodology for determining the optimum re-peening schedule to increase the fatigue life of laser peened aircraft components

Surface enhancement techniques, such as laser peening, have wide applications in the aerospace industry. They increase the structural component's life by imparting compressive residual stresses around the critical locations where the cracks are likely to initiate and later propagate leading to component failure. However, the compressive residual stresses can relax due to the loading conditions and reduce the laser peening effectiveness. Under such a condition, re-peening or re-laser peening a component already in service can further increase its component life. This research develops a method to predict the optimum re-peening time for maximum fatigue life under realistic loading conditions. An optimization problem is set up to illustrate the application of this method to an aircraft lug problem. Results from the investigation indicate that re-peening this component ∼50-55% of its expected fatigue life maximizes the component's fatigue life. The proposed approach, proven to be able to obtain optimal process parameters for improving the fatigue resistance of the component, can significantly reduce the costs for experimental testing.