Foreign object damage (FOD) is a common occurrence in many applications but is the nemesis of aircraft engines and structures. Because these components are designed for minimum weight and section thickness, they are particularly vulnerable to any surface damage that will initiate fatigue failure. The formation of any nick or dent in the surface, provided that it is not accompanied by high residual compression, will produce a stress concentration factor. Factors for foreign object damage can be as high as 5.0, depending upon the nature of the damage and the shape of the feature produced.
Foreign object damage is produced by flying debris in the fan and compressor sections of aircraft engines and ground-based turbines, on landing gear and other structural components exposed outside the aircraft. Even maintenance and general operation of an aircraft can result in internal FOD from loose tools, cargo, and so on during maintenance and use.
Damage from foreign object debris occurring in high-stress fatigue critical areas can lead to catastrophic failure. The introduction of a layer of compression deeper than the depth of the damage using LPB® can completely mitigate foreign object damage. This has been demonstrated in titanium alloys such as Ti-6-4, 7075-T6 aluminum for structures, and 300M and 4340 structural high strength steels.
- landing gear
- aircraft wings
- compressor sections of engines
LPB® force to two sides of the component simultaneously can produce through-thickness compression in thin sections such as the leading edge or trailing edge of blades and vanes. The zone of high compression can extend back a significant distance from the edge, providing spectacular tolerance to foreign object damage during impact on the edge of the blades.
Thousands of LPB® processed airfoils are currently flying to mitigate foreign object damage and extend component life in aircraft engines without changing either the alloy or the design of the component.