Vibratory peening for the fatigue life improvement of aerospace parts

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Most metallic aerospace parts are surface treated to improve their fatigue lives. Conventional shot peening consists of projecting hard particles at high velocity onto a ductile metallic surface. The process induces compressive surface residual stresses, which is beneficial for improving fatigue life, but also roughness, which decreases fatigue life. Shot peened parts are often surface treated for improving their surface finish. Vibratory peening is a vibratory finishing process that induces compressive residual stresses comparable to those induced by shot peening, but for a much better surface finish. The process could therefore be an interesting alternative to shot peening since it combines two steps in one. The objective of this work is to understand the vibratory peening treatment effects of a Canadian company, VibraFinish, on materials used in gas turbine engines manufactured by Safran. This scientific study will investigate the effects of vibratory peening on roughness, hardness, residual stresses as well as microstructural changes for high strength steel and titanium alloys so as to assess its potential at improving fatigue life. The work will be carried out by a MSc student supported by a research associate and engineers from the industry. If the process' potential at improving fatigue life is scientifically demonstrated, this project will be the grounds for a more important collaborative research and development project between VibraFinish, Polytechnique Montréal and Safran. This project would aim at better understanding the process' effects in a view of optimizing it. As such, this proposed project could help a Canadian company to establish its leadership in a competitive market as well as providing Canada-based Safran companies with a new process of improved performance.