High Cycle Fatigue Performance in Laser Shock Peened TC4 Titanium Alloys Subjected to Foreign Object Damage
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High Cycle Fatigue Performance in Laser Shock Peened TC4 Titanium Alloys Subjected to Foreign Object Damage Sihai Luo, Xiangfan Nie, Liucheng Zhou, Yiming Li, and Weifeng He (Submitted July 1, 2017; in revised form October 24, 2017; published online January 29, 2018) During their service, titanium alloys are likely to suffer from "/>the foreign object damage (FOD), resulting in a decrease in their fatigue strength. Laser shock peening (LSP) has been proved to effectively increase the damage tolerance of military engine components by introducing a magnitude compressive residual stress in the near-surface layer of alloys. In this paper, smooth specimens of a TC4 titanium alloy were used and treated by LSP and subsequently exposed to FOD, which was simulated by firing a steel sphere with a nominal velocity of 300 m/s, at 90° with the leading edge of the LSP-treated region using a light gas gun. All impacted specimens were then subjected to fatigue loading. The results showed that LSP could effectively improve the fatigue strength of the damaged specimens. The effect of LSP on the fatigue strength was assessed through fracture observations, microhardness tests and residual stress analyses. The residual stresses due to the plastic deformation caused by LSP and the FOD impact, which were found to play a crucial role on the fatigue strength, were determined using the commercial software ABAQUS. Keywords
fatigue strength, foreign object damage, laser shock peening, residual stress, TC4 titanium alloy
1. Introduction Foreign object damage (FOD) refers to the damage caused by the impact of small, hard foreign objects such as stones, sand and iron during takeoff and landing of aircraft. The impact on the leading edge of the aero-engine fan or compressor blades can lead to the initiation and quick propagation of fatigue cracks and subsequent fracture in correspondence of the damage notch. FOD has come to be considered one of the main events affecting the fatigue strength of the aero-engine fan or compressor blades (Ref 1-4). Thus, it is of great significance to improve the fatigue strength of titanium alloy blades to resist the effect imparted by FOD. Laser shock peening (LSP) has been previously proposed as a technique to improve fatigue strength and the resistance of fatigue crack growth (FCG) (Ref 5-12). For example, Huang et al. (Ref 10, 11) investigated the effects of different LSP impacts and shocked areas on the FCG
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11665-018-3172-6) contains supplementary material, which is available to authorized users. Luo Sihai, Nie Xiangfan, Zhou Liucheng, and Li Yiming, Science and Technology on Plasma Dynamics Laboratory, Air Force Engineering University, 1st Baling Road, XiÕan 710038 Shaanxi, China; and He Weifeng, Science and Technology on Plasma Dynamics Laboratory, Air Force Engineering University, 1st Baling Road, Xi’an 710038 Shaanxi, China; and Institute of Aeronautics Engine, School of Mechani
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