Experimental Investigation of Effects of Polishing Process on Surface Residual Stress of TC4 Blade Based on Sensitivity Analysis

The residual compressive stress on polished surfaces can significantly delay the initiation of microscopic flaws, and improve the fatigue strength of engineered components. Reasonable selection of polishing parameter ranges plays an important role in controlling residual compressive stress on finished surface, which is closely related to the service performances of aero-engine blade. In order to investigate the influence of each process parameter on residual compressive stress and obtain the optimal parameter ranges for the maximum and stable residual stress range, the sensitivity analysis method was presented in this study. The polishing experiments were designed by using four-factor three-level Central-Composite design theory for TC4 titanium alloy thin-walled blades. Based on the residual stress prediction model developed utilizing a multiple regression method, a global relative sensitivity analysis was conducted to identify the significant and insignificant parameters. Then the stable range and the instable range were divided based on sensitivity curves, and a parameter range optimization method was subsequently presented. Finally, the optimal parametric ranges for residual stress in polishing process were obtained as follows: rotation speed within [9500 r/min, 11,000 r/min], feed rate within [100 mm/min, 200 mm/min], contact force within [0.6 N, 1.8 N] and row spacing within [6 mm, 7 mm].