Fatigue Life Improvement with Surface Treatments other than Shot Peening

Risk of fatigue failure is the primary limitation on performance and life of rotorcraft and increases the cost of ownership by increasing maintenance and inspection costs. Shot peening is currently used to enhance fatigue life. However, shot peening does not produce a compressive layer deep enough to arrest a fatigue crack detectable with NDI methods. Laser shocking provides the necessary depth, but is expensive and introduces logistical problems. Low plasticity burnishing (LPB) has already been demonstrated to provide the required depth of compression to arrest detectable fatigue cracks. LPB is a practical shop floor technology currently in commercial production. The Phase I effort would demonstrate arrest of existing flaws and restoration of fatigue life in test coupons using robotic LPB processing. Phase II extends the effort to actual rotocraft dynamic components using roller tool designs to access fatigue critical features with robotic tool positioning. LPB processing of fatigue critical dynamic components will increase life and performance of rotorcraft, reduce the required inspection time costs, and improve aircraft safety and reliabilityBENEFITS: The primary benefit to NAVAIR of introducing LPB technology will be extended life and reduced cost of manufacturing fatigue critical rotorcraft components, improved time on wing and reducing maintenance and inspection costs and requirements, first for the V-22 program and then extending to other aircraft. Potential applications and commercial opportunities for low plasticity burnishing (LPB) as a means of improving the fatigue performance of aircraft dynamic components are vast. LPB is already approved by NAVAIR for application to the F404 engine LPC1 vanes and blades used on the AV-8 B Harrier to enhance fatigue performance and is in production mitigating fretting fatigue in titanium alloy hip implants. The anticipated market for LPB in aircraft structural and dynamic components is anticipated to approach $100M during the next decade.