On the usage of pulsator data within the load spectra assessment of gears

Tooth root fatigue fracture is one of the most critical gear failure modes. This is due to the fact that it may cause a sudden interruption of the power flow within the gearbox, which typically results in the complete failure of the transmission. Therefore, a crucial design aspect is the accurate characterization of the gear bending fatigue strength. Here, designers can rely on experimental tests in order to obtain data related to their specific industrial reality. Within this context, pulsator test, also called Single Tooth Bending Fatigue (STBF) test, is the most adopted experimental methodology. As such tests are performed only on selected teeth within a testing device and not on all teeth of a running gear pair, the pulsator experimental outcome has to be elaborated before using it in the actual design phase. Depending on the elaboration methods, several SN curves can be obtained, and those curves will differ from the one predicted by the standards (e.g. ISO 6336 and ANSI AGMA 2001-D04). Furthermore, different SN curves will provide a different assessment when load spectra are considered. Here, the usage of data obtained from pulsator tests is analyzed within the phase in which load spectra are considered while designing a gear. In particular, this article discusses the differences between various elaboration methodologies and an assessment based on standardized curves.