Advanced models for helicopter gearbox health management

Tryon Robert G., Holmes Richard, Pulikollu Raja V.

Abstract:
PHM investments have enabled diagnostics of up to 70% of faults. The remaining 30% require advanced modeling and monitoring of specific subsystems such as gear trains. Developing PHM from empirically-based testing is very expensive and must be reworked for every gear system design change. Finite element analysis combined with long crack modeling cannot predict failures because damage initiation is physically small and rapidly grows to failure. VEXTEC developed techniques for modeling damage at the fundamental microstructural level and these techniques are applied to gear system PHM. The modeling properties of geometry, composition, material characteristics, case hardness, core hardness, case depth, design ratios of case to tooth thickness, surface finish, and machining are directly and explicitly addressed in the formulation of a micromechanical material model. The physics-based failure models allow for explicit prognosis of air vehicle gear components and systems. This work provides for successful modeling of the effects of tooth bending and contact fatigue to advance the understanding of this failure mode as a critical and new approach to aerospace application prognosis. The technology in development will be combined with active sensor measurements for accurate reliability prediction of gear health. Thereby these models can cover the remaining 30% of failure modes in less time and lower cost than other techniques available today.

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