PSI - Issue 80

Francesco Manni et al. / Procedia Structural Integrity 80 (2026) 177–186 Francesco Manni/ Structural Integrity Procedia 00 (2019) 000–000

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simulations have been carried out to assess the impact of overload on fatigue performance: the first on a gear that had not been subjected to overload, and the second on the same gear after undergoing this problematic load. The applied fatigue cycle represented a full meshing event of a single tooth. As shown in Fig. 12, in the same region where a shift from compressive to tensile residual stresses has been previously observed, the safety factor in the plasticized gear is significantly lower compared to the non-overloaded case. This clearly demonstrates that overload exposure degrades the fatigue resistance of the gear. A component that has undergone not tolerable plasticization is therefore more prone to premature failure during operation. a b

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Fig. 12. (a) safety factor of the wheel not subjected to overload, (b) safety factor of the wheel subjected to overload.

6. Conclusion and future work In this work, a methodology has been presented to analyse the influence of a plasticizing overload on the stresses induced by the nitriding treatment on a gear wheel. Additionally, an analysis was carried out to study how this alteration affects high-cycle fatigue resistance. First a methodology was introduced to simulate these stresses within a FE environment without altering the geometry under analysis. Several Finite Element simulations of the meshing were conducted. Initially, two different static meshing configurations were simulated. The first was characterized by the maximum bending moment at the tooth root, which, however, turned out to be not very damaging, as the excessive deformation of the tooth shifted the contact also onto the next tooth, thereby limiting the generated stresses. Therefore, the second configuration was also set to maximize the bending moment but ensured that the contact occurred on a single tooth. From this, it was observed that the stresses imposed by the contact effectively induced plasticization, with a peak at the boundary between the nitrided and non-nitrided layers, which altered the stress state. Subsequently, a complete meshing cycle of a tooth was simulated to effectively evaluate how the overall stress state varied, showing how this alteration, due to plasticization, actually compromises the favourable compressive stresses precisely where crack nucleation was observed. Finally, fatigue analyses were performed on the component both with and without the plasticizing overload. The results have shown that the component which had not experienced any overload had a better resistance at high cycle fatigue. Furthermore, it was observed that the area with the lowest safety factor corresponded to the zone where crack nucleation later occurred, eventually leading to failure. In the future, experimental campaigns might be necessary to assess the robustness of the method in estimating damage induced on a gear wheel. In parallel, it might be important to analyse different tooth geometries and contact ratios in order to identify potential countermeasures against this type of damage. Specifically, by evaluating the use of a higher contact ratio for the same application, in order to achieve a better load distribution. References

Aubert & Duval. (2016). GKH ® (W-YW) 33CrMoV12-9 . https://www.aubertduval.com/wp-content/uploads/2025/01/Brochure-GKH.pdf Barbieri, S. G., Mangeruga, V., Giacopini, M., Laurino, C., & Lorenzini, M. (2019). A finite element numerical methodology for the fatigue