The load capacity of power transmitting gears can be limited by different failure modes. Standardized calculation methods acc. to German (DIN) or International (ISO) standard are available for rating the pitting resistance and bending strength of gear teeth. A further kind of fatigue damage is micropitting that is most frequently observed on case carburized gears.
Micropitting is controlled by the conditions of the tribological system of tooth flank surface and lubricant. The oil film thickness has been found to be a dominant parameter. Lubricant of base oil and additive, operating conditions, surface roughness and gear geometry are known as important influence factors on the micropitting load capacity.
In continuous work over several research projects major influences on the micropitting load capacity of gears were systematically investigated.
ForevaluatingtheinfluenceoflubricantstheFZGmicropittingtestwasdeveloped. Resultsontheinfluenceof certain parameters such as oil temperature, surface roughness or material were determined by variation of the test conditions.
Within the scope of actual research work some basic influences of gear geometry, gear size and operating conditionswereinvestigated.Forthispurposeanextensivetestprogramonspurandhelicalgearsofdifferent sizes and different gear geometry has been carried out. Based on the results of the previous and actual investigations an enhanced calculation method to determine the micropitting load capacity of practical gear units was developed.

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