Evolution of a laser shock peened residual stress field locally with foreign object damage and subsequent fatigue crack growth. Acta Materialia, http://dx.doi.org/10.1016/j.actamat.2014.09.032 conditions. The ballistic FOD impacts were introduced by impacting a cube edge at an angle of head-on (0 degrees) to the leading edge. The residual stress distributions have been mapped by synchrotron X-ray diffraction prior to cracking and subsequent to short (~1 mm) and long (up to 6 mm) crack growth. 2The results suggest that the local residual stress field is highly stable even to the growth of relatively long cracks.

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a b s t r a c tForeign object damage (FOD) to the leading edge of aerofoils has been identified as one of the main life-limiting factors for aeroengine compressor blades. Laser-shock peening (LSP) has been proposed as a means of increasing the material's resistance to such impact damage. In this work, a three-dimensional finite element (FE) model has been developed to simulate the residual stresses due to head on (0°) and 45°impacts by a cuboidal projectile on aerofoil specimens treated with LSP. The Johnson-Cook (JC) material model was employed to describe the strain rate-dependent material behaviour; whilst the JohnsonCook dynamic failure model was considered in 45°FOD simulation, where significant loss of material occurred. The strain rate sensitivity of the model at selected high strain rates was assessed against the data from the literature. The numerical results from the simulation of head-on impact were compared with the measurements by depth-resolved synchrotron X-ray diffraction on the mid-plane. The models were then used to predict the 3D residual stress distributions due to 0°and 45°FOD impacts, and the results were compared with the strain maps obtained from high-energy synchrotron X-ray diffraction. Good to excellent correlations between the simulations and the measurements have been found.

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