Gear tooth wear is a very difficult phenomenon to predictanalytically. The failure mode of wear is closely correlated to thelambda ratio. Wear can be the limiting design parameter forlong-term durability. Also, the failure mode of wear can manifestinto more sever failure modes such as bending. Presented is afailure analysis in which this occurred.
A legacy aerospace gear mesh experienced nine failures within atwo year time period. The failures occurred after more than eightyears in service and within tight range of cycles to one another.Each failure resulted in the loss of all gear teethwith originsconsistent with classic bending fatigue. None of the failuresweredetected prior to tooth loss.
Non-failed gears, with slightly lower time than the failedgears, were removed from service and inspected. Gear metrologymeasurements quantified a significant amount of wear. The flankform of these worn gears was measured and the measured data used toanalytically predict the new dynamic load distribution and bendingstress. To predict if the failure mode of wear was expected forthis gear mesh, an empirical relationship of wear to lambda ratiowas created using Rolls-Royce field data from multiple gear meshesin multiple applications.
The empirical understanding of wear coupled with the analysiswas used in an analytical design of experiments (ADOE). The resultsof the ADOE were then used to guide design changes. Presented arethe metallurgical failure analysis findings, dynamic gear meshanalysis, the empirical wear rate curve developed, results of theADOE, and design changes.
- Edition:
- 07
- Published:
- 10/01/2007
- Number of Pages:
- 13
- File Size:
- 1 file , 1.1 MB
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