Design Tool for Fatigue Sensitive Steel Rotorcraft Components

In modernizing its rotorcraft fleet, the US Army has identified the pressing need to increase the horsepower of existing rotorcraft transmissions without sacrificing component life, as well as the need for new transmission designs with higher power density capacity and improved durability. The concept of improving fatigue resistance without enlarging the design envelope or imposing changes that would require new part qualifications is attractive from both cost and time savings standpoints. Data and results from Phase I have provided new information concerning laser shock peening application and residual stress response in carburized Pyrowear 53 steel. Laser peening can improve fatigue life by achieving high levels of residual compression to significant depths in a given part. Promising modeling work associated with the Phase I physical testing has laid the foundation for a computer design tool, enabling laser peening residual stress prediction in combination with other manufacturing processes, such as prior heat treating. Phase II will characterize fatigue life improvement in carburized and hardened Pyrowear 53 steel by laser shock peening. Experimental results will be used to aid the development, validation and commercialization of a process modeling design tool for predicting the residual stresses which drive the fatigue life improvement.