Is the Civil Aerospace Industry Ready to Implement Laser Shock Peening into Maintenance Environment? Questions to Be Answered and Minimum Requirements from Aircraft Manufacturer's Perspective

摘要

Laser Shock Peening (LSP) system, involving complex set up and tooling, is not practical at all for in-service use (not compatible with airline maintenance constrains). To make LSP applicable at Maintenance Repair and Operations (MRO) and ensure reasonably simple setup and easy transportability to all around the world requires developing a "portable" device (i.e. low energy laser). The application of LSP as retrofit solution for in service commercial aircraft is particular challenging and currently no applications are reported. Applying LSP as a structural modification in critical component of in service commercial aircraft implies treatment at the MRO all around the world during already scheduled maintenance to avoid Aircraft on Ground situation, which can cost tens of thousands dollars a day. It is a common understanding that the depth of compressive residual stress over 1 mm can be achieved only if high energy laser (i.e. large laser spot) is used. It is demonstrated in this paper that low energy LSP system (< 200 mJ, pulse width of < 25 nsec) and associated small laser spot size (< 1 mm diameter) can determine high compressive stress in the near surface of typical aeronautical Al alloy and compression depth above 1 mm. This residual stress profile is sufficient to extend the fatigue lives of critical components opening the door for development of portable LSP devices requiring low energy laser. The paper includes the investigation of low energy LSP system from residual stress characterization to fatigue life response of 7175-T7531 aluminum alloy. Finally, the authors review the minimum requirements of LSP portable device to ensure the compatibility with the operational environments typical of MRO.