In the design phase, several analytical calculation methods are adopted in order to avoid those damage phenomena (e.g., ISO 6336 series). ISO/FDIS 10825-1 classifies the most classical failure mode within two main macrocategories: tribological damages (i.e., scuffing and wear) and fatigue damages (i.e., contact fatigue and bending fatigue).
Both ISO/FDIS 10825-1 and ANSI/AGMA 1010-F14 enlist several failure mechanisms that can affect gears. Due to their peculiar working principles, several failure mechanisms may occur in gear. Gears are mechanical components that, through the meshing of profiles, transmit power between two axes with an almost constant angular speed ratio. Then, a methodology based on statistic of extreme is adopted for the purpose of estimating the gear SN curve. The teeth SN curve has been estimated by means of a statistical model developed considering Murakami’s idea of nonpropagating crack. This paper deals with the statistical ones that is the estimation of the gear SN curve starting from the teeth one. However, as in STBF test THERE IS no sliding/rolling contact and as the specimens are teeth rather than gears, some differences occur between the test conditions and those of the real case. In order to characterize a gear for this phenomena, Single Tooth Bending Fatigue (STBF) tests are the most performed ones. Among the several gear failures, tooth root bending fatigue is considered as the most dangerous one because it implies the stoppage of the whole gearbox.
Being able to properly predict gear failure is a key aspect to achieve a reliable light-weight gearbox.
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