PSI - Issue 57

208 10

Dr.-Ing. D. Jbily et al. / Procedia Structural Integrity 57 (2024) 199–216 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

According to the ISO 6336-2 (2019) and ISO 6336-5 (2016) standard, the number of load cycles for 1% probability of appearance of the first pitting on the pinion is 1.58*10 6 cycles and that for a widespread pitting is 10.12*10 6 cycles (75 hours). This correlates with the experimental results where widespread spalling was observed on case-hardened gears after 8.8*10 6 load cycles (on average). However, when comparing the lifetime calculated according to the standard with that obtained experimentally on the shot peened gears, macropitting occurred after 18*10 6 cycles and even after 31.55*10 6 cycles, spalling is not widespread. The service life is increased by more than 60%. This improvement can be explained by the increase of residual compressive stresses into the surface layer after shot peening treatment.

3.4. Tooth profile deviation analysis

The deviation of tooth profile is measured before and after the test. These measurements are carried out using a Leitz three-dimensional machine assisted by its Quindos measurement software. Examples of the results of the gear profile control are shown in Fig. 9 and Fig. 10 below. Micropitting causes tooth profile deviations for the gear. These deviations extend between the active root diameter (68.25 mm) and the pitch diameter (73.64 mm). The maximum profile deviation of pinion gear occurs at the dedendum as shown by the profile deepening in this zone. The tooth profile of the gear wheel also shows deviations due to micropitting in the dedendum zone, between the active root diameter (104 mm) and the pitch diameter (109.54 mm), as shown in Fig. 10. The shape of the profiles and the depth of the material loss (several tens of microns) show that micropitting is accompanied by wear on the tooth flanks.

Fig. 9. Pinion tooth profile deviations at the end of test