**5. Conclusions**

Based on the 3D-FEM and TM, this paper has analyzed the TSCS of spur gears with three di fferent influence factors: TPD, ME and LCM. In particular, it has analyzed the interactions between PD, ME and LCM, and their influence degrees on the TSCS. Throughout the full paper, there are several conclusions that need to be summarized, as follows:


**Author Contributions:** Writing—original draft, Q.L.; Writing—review and editing, L.X. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the "Research on Reliability Theory and Method of Total Fatigue Life for Large and Complex Mechanical Structures" of Natural Science Foundation of China and Liaoning Province, gran<sup>t</sup> number U1708255.

**Conflicts of Interest:** The authors declare no conflict of interest.
