Landing Gear Trunnion Pins

Aerospace-grade materials such as 4340M, 300M, and HY-TUF are selected for their ultra-high strength-to-weight ratios and fatigue resistance under load reversal conditions. These alloys undergo vacuum heat treatment cycles, including double tempering and cryogenic stabilization, to achieve uniform microstructures and suppress retained austenite. Shot peening is applied to critical surfaces to induce compressive residual stresses, delaying crack initiation under high-cycle fatigue scenarios. Grain boundary segregation and hydrogen embrittlement are controlled through post-heat treatment bake-out and vacuum degassing. 

Precision fit between the landing gear trunnion pins and housing bores directly governs the stability of the gear pivot during operation. Interference and transition fit profiles are calculated based on thermal expansion coefficients, loading vectors, and lubrication regimes. Pins are manufactured to match H7/h6 or JS5 tolerance zones, depending on the bushing material and expected deflection behavior. Surface roughness profiles (Ra ≤ 0.2 µm) are maintained to reduce friction-induced micro-abrasion and to allow for hydrodynamic lubrication film formation. The fit ensures predictable load distribution across the bushing length and prevents bushing ovalization or pin fretting.