This paper presents an approach to gear service life determination. The proposed approach relies on the assumption that the dynamic loaded gears are made from case hardened steel, are loaded with defects and deviations as is practically normal, and an initial crack in the surface appears that slowly propagates through the tooth root. The justification of usage linear elastic crack mechanic is tested. First calculation step is the determination of the crack shape by using virtual crack extension method. After it the dependence of stress intensity factor from crack length is numerically calculated. On the end the service life of such cracked gears by using numerical integration of modified Paris equation is determined. The calculated service life of gear should be compared with the requirements. The expected service life of gearbox is about one million kilometres covered by 5 percent probability of failure. To get the feeling about the sense of crack propagation calculations one should consider the completely happening during the total gear service life: the period without crack and the period when the crack occurs. The crack could participate about 20 % or even more on the total gear service life. During short crack presence, let say less than 1 mm, the gear pair is still full operationally. So it is more than reasonable to examine the crack propagations in tooth roots of gearbox gears. Considering the integrity of gearbox it is necessary to examine all other components that to be found in the gearbox. The treated case is the only one contribution to the modern computations by which the designers control the efficiency of components. The same procedure can be used on each component that is loaded by cracks.
Service life of cracked gearbox gears
Lebensdauer von rissbehafteten Getriebezahnrädern
2000
8 Seiten, 13 Bilder, 1 Tabelle, 3 Quellen
Conference paper
English
Service life of cracked gearbox gears
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