Experimental and Numerical Investigation on Fatigue Limit Improvement of Laser Shock Peening on Airfoil Specimens Subjected to Foreign Object Damage

Foreign object damage (FOD) has been a critical issue for fan and compressor blades in aero-engines due to the cause of high cycle fatigue (HCF) failure. To address it, anti-fatigue design is imperative. In this paper, laser shock peening (LSP) was employed to improve fatigue resistance of the airfoil specimens with FOD. Systematic experimental investigations were carried out to determine the notch geometry, residual stress, and cumulative plastic damage are the dominant factors in improving HCF resistance. Compared with the as-received specimens, LSPed specimens exhibited fatigue limit increase ranging from 6.4% to 47.4%, which was affected by the scatter of the notch geometry. Therefore, detailed finite element analyses were conducted to determine the distributions of residual stress and plastic strain of individual notches and quantify the superimposed effects of FOD and LSP on fatigue limit. Accordingly, a modified Kitagawa–Takahashi diagram was proposed, with a maximum error within 10% for different depths of notches.