The load capacity of power transmitting gears can be limited bydifferent failure modes. Standardized calculation methods acc. toGerman (DIN) or International (ISO) standard are available forrating the pitting resistance and bending strength of gear teeth. Afurther kind of fatigue damage is micropitting that is mostfrequently observed on case carburized gears.
Micropitting is controlled by the conditions of the tribologicalsystem of tooth flank surface and lubricant. The oil film thicknesshas been found to be a dominant parameter. Lubricant of base oiland additive, operating conditions, surface roughness and geargeometry are known as important influence factors on themicropitting load capacity.
In continuous work over several research projects majorinfluences on themicropitting load capacity of gears weresystematically investigated.
For evaluating the influence of lubricants the FZGmicropittingtest was developed. Results on the influence of certain parameterssuch as oil temperature, surface roughness or material weredetermined by variation of the test conditions.
Within the scope of actual research work some basic influencesof gear geometry, gear size and operating conditions wereinvestigated. For this purpose an extensive test program on spurand helical gears of different sizes and different gear geometryhas been carried out. Based on the results of the previous andactual investigations an enhanced calculation method to determinethe micropitting load capacity of practical gear units wasdeveloped.
In accordance to the existing standardized calculation methodsregarding pitting resistance and bending strength the proposedrating formulas can be used to evaluate the risk of micropittingrespectively to determine a safety factor for micropitting on casecarburized gears.
The calculation method is based on the result of themicropitting test as a tribological parameter for the lubricant inuse but enables the gear designer furthermore to take majorinfluences as operating conditions, gear geometry and gear size ofthe actual application into consideration if rating themicropitting load capacity of a gear.
The paper summarizes important results of the continuousexperimental investigations and introduces the proposed calculationmethod for rating the micropitting load capacity of case carburizedgears.
- Edition:
- 04
- Published:
- 10/01/2004
- Number of Pages:
- 15
- File Size:
- 1 file , 650 KB
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