PSI - Issue 80

Simone Messina et al. / Procedia Structural Integrity 80 (2026) 232–243 Simone Messina/ Structural Integrity Procedia 00 (2019) 000–000

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absence of tooth micro-geometry and the occurrence of localized contact in peripheral areas, resulting in pronounced stress concentrations. The significance of micro-geometry in gear analysis is clearly evident comparing Fig. 6(a) and Fig. 6(b), but also comparing Fig. 6(c) and Fig. 6(d). Incorporating micro-geometry leads to a more favorable distribution of contact across the tooth surface, with interactions tending to occur predominantly in the central region of the tooth profile. This centralization of contact is highly beneficial, contributing to a properly stress distributions, enhanced operational safety, and lower noise emissions. Additionally, a key observation is that the contact pattern becomes more confined to the central portion of the tooth, rather than extending toward the edges. This indicates a more controlled and desirable load transmission path. A further improvement is observed in the stress distribution Fig. 6(d): in earlier configurations, the highest stress values were localized near the tooth edges due to contact-induced stress concentration. In contrast, with the inclusion of microgeometry, the maximum stress has shifted toward the tooth with the greatest effective contact area, an outcome that aligns with expected mechanical behavior and indicates a realistic and reliable model also including the microgeometry. a b

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Figure 6 Static model result: (a) contact status no microgeometry model; (b) contact status microgeometry model; (c) maximum principle value of stress no microgeometry model; (d) maximum principle value of stress microgeometry model.

4. Full gear mesh simulation Lastly, the full meshing cycle of a single gear has been simulated, covering the entire meshing operation. Specifically, a rotation of 22 degrees, measured on Gear 2, has been simulated. 22 degree is the value to simulate the meshing of the 11 teeth and to have at least one tooth that experience the full contact sequence, from the start of engagement to the end. The same procedure used for the static analysis has been followed and each simulation has been compared. The model implemented in MarcMentat has been identical to that one used for the static analysis, maintaining the same constraints and rigid links but, in this case, 22 degrees of rotation have been simulated divided in a specific number of time step. To evaluate the influence of the time step on the fatigue analysis, simulations involving only the gear have been conducted