Gear tooth wear is a very difficult phenomenon to predict analytically. The failure mode of wear is closely
correlated to the lambda ratio. Wear can be the limiting design parameter for long–term durability. Also, the
failure mode of wear can manifest into more sever failure modes such as bending. Presented is a failure
analysis in which this occurred.
Alegacyaerospace gearmesh experienced nine failures within atwo yeartime period. The failures occurred
after more than eight years in service and within tight range of cycles to one another. Each failure resulted in
thelossofall gearteeth with originsconsistentwith classicbending fatigue. Noneofthefailuresweredetected
prior to tooth loss.
Non–failed gears, with slightly lower time than the failed gears, were removed from service and inspected.
Gear metrology measurements quantified a significant amount of wear. The flank form of these worn gears
was measured and the measured data used to analytically predict the new dynamic load distribution and
bending stress. To predict if the failure mode of wear was expected for this gear mesh, an empirical
relationship of wear to lambda ratio was created using Rolls–Royce field data from multiple gear meshes in
multiple applications.