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Predicting the Effects of Surface Properties of Laser Shock Peened TC4 Titanium Alloy
B-Y. Su, H. Wang, Y-P. Cao, G-R. Hua and J-B. Wang

The surface properties of laser shock peened TC4 titanium alloy on the material’s fatigue life growth rate are investigated and predicted. The fatigue life is predicted using the crack growth rate model, which consists of the surface roughness and surface residual stress. The theoretical model is verified using fatigue life test results. The surface roughness and residual stress post laser shock peening (LSP) were carefully evaluated using the optical profiler and X-ray diffraction (XRD) method. Results showed that there was an increase in the surface roughness with an increase in the laser power density and a decrease with the increasing overlapping rate and the number of impacts caused by the micropit and convex deformation on the surface. The surface roughness shows a remarkable impact on the fatigue life. Increasing the power density simply cannot effectively increase the fatigue life, whereas increasing the overlapping rate has the most remarkable impact on the fatigue life growth rate.

Keywords: Nd:YAG laser, TC4 titanium alloy, laser shock peening (LSP), surface roughness, residual stress, fatigue life growth rate

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