The high performance required from aerospace gears placesstringent requirements upon the metallurgical quality, geometry,and surface finish of mating parts. In an effort to meet theirmission requirements, aerospace gears are often engineered tooperate near the upper bounds of their theoretical designallowables. Due to this, scuffing is a primary failure mode foraerospace gears.
It was previously shown that specimens having an isotropicsuperfinish using chemically accelerated vibratory finishing had animproved performance in Rolling/SlidingContact Fatigue (R/SCF)testing. Isotropic superfinishing improved R/SCF resistance up tonine times that of baseline test specimens. These tests alsodemonstrated the ability to successfully carry 30 percent higherloads for at least three times the life of the baselinesamples.[1]
A study was then conducted on actual gears having an isotropicsuperfinish. This study showed isotropic superfinishing technologyincreased a gear’s resistance to contact fatigue by a factor ofthree, and increased bending fatigue resistance by at least 10percent. [2] This increase in gear performance translates toreduced operation and sustainment costs, and also offers thepotential for weight reduction in new transmission designs.
The present paper will discuss an additional study which isunderway to determine and compare the scuffing resistance ofisotropic superfinished aerospace gears to that of baseline groundgears. Sample gears were made from case carburized SAE 9310. Thesetests were conducted using a method that progressively increaseslubricant temperature until scuffing occurs, rather than thetraditional load increasingmethod used in FZG testing rigs. Theresults of the current testing reveals that isotropic superfinishedSAE9310 specimens show at least a 40° F higher lubricanttemperature at the point of scuffing compared to as-ground baselinegears. Based on these results and the previous studies, it wasconcluded that this isotropic superfinishing technology should beincorporated in all future aerospace gear designs. A later paperwill report on similar scuffing testing performed on AMS 6308 gearsdue to run–outs achieved by both the baseline and isotropicsuperfinished samples during the current procedure.
- Edition:
- 05
- Published:
- 10/01/2005
- Number of Pages:
- 12
- File Size:
- 1 file , 1.8 MB
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