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asset readiness and reducing total ownership costs. This paper
details a preliminary scaled gearbox test plan, results accumulated
from these tests, and specific discussion of the use of health
indicators with leading corrosion models is also addressed.

Motivation

Mechanical components, such as gears and bearings, are
generally designed for "near-infinite" service lives based on their
expected operational stress levels. In some cases, however, these
components are subject to early failure due to various life-limiting
damage scenarios, such as corrosion. Corrosion and related
damage mechanisms significantly affect material strength
properties in gearbox components, thereby reducing the
component's the load carrying capacity and ultimately shortening
its useful lifetime. The intrusion of contaminants into the gearbox
lubricant can accelerate damaging chemical reactions at the surface
of the material and reduce the effectiveness of the lubricant film at
contact surfaces. Modern methods for estimating service life of a
component, such as life cycle counting, may not directly account
for the effects of corrosion, thereby providing overly optimistic
fatigue life estimates.
High power gearbox systems, such as those designed for
fixed wing and rotorcraft air vehicles, are applications of
significant concern in which a failure will ultimately jeopardize the
entire vehicle and the safety of the crew. Tooth surface corrosion
can lead to compromised power transmission capabilities and
potentially catastrophic failures. Corrosion driven problems are
aggravated in vehicles that operate in marine environments where
moisture absorption and direct salt water ingestion in the gearbox
are possible. Diffusion of ambient moisture into lubricant is a
primary mode of water ingress. During operation, the combination
of corrosion and cyclic stress loading, known as corrosion fatigue,
accelerates degradation and reduces component remaining useful

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