Effect of co-strengthening of laser impact/mechanical shot peening on fatigue performance of TC4 titanium alloy damaged by foreign objects

Abstract

Aiming at the problem that the fatigue performance of aeroengine blade leading edge was seriously degraded after foreign object damage（FOD）, the surface of TC4 titanium alloy thin wall specimen was treated by laser shock/mechanical shot peening, and the residual stress gradient distribution on the specimen surface before and after the composite strengthening was measured by X-ray diffraction method； The high order vibration fatigue life of TC4 titanium alloy thin wall specimens before and after treatment was tested by electromagnetic vibration table, and FOD was introduced into the specimen surface by fabricating pits of different shapes with a hardness tester； The fatigue fracture surface was analyzed by SEM； The evolution of residual stress distribution on the specimen surface before and after FOD was simulated by finite element dynamic numerical simulation, and the mechanism of the influence of the composite strengthening layer on the notch fatigue performance of FOD was revealed. The results show that the average fatigue life of the composite strengthened FOD specimen is 370% and 60% higher than that of the non strengthened FOD specimen and the non strengthened FOD specimen, respectively. The deep residual compressive stress field（thickness 500 μm）formed on the surface layer of the specimen after composite strengthening is an important reason for increasing the fatigue life of FOD specimen.

Keywords

• laser shock peening
• shot peening
• fod
• fatigue
• numerical simulation