Dynamic Characteristics Analysis of Needle Roller Bearings in Planetary Gear Trains with Consideration of Inner Bore Spalling Defects of Planet Gears

Driven by the growing demand for higher efficiency and load-bearing capacity in fields such as new energy vehicles and heavy-duty engineering machinery, planetary gear sets are increasingly operating at elevated rotational speeds, coupled with a corresponding expansion of their revolution radii. This dual trend directly induces a substantial surge in centrifugal acceleration acting on the internal needle roller bearings. Under the cyclic stress inherent to transmission operations, such enhanced acceleration not only accelerates the initiation of spalling faults on the inner bores of planet gears but also exacerbates the propagation and deterioration of these faults throughout the service life. To elucidate the influence mechanism of inner bore spalling on the dynamic response of planetary gear bearings, this study develops a specialized dynamic model. This model explicitly incorporates the compound kinematic effects of simultaneous rotation and revolution, thereby ensuring a high-fidelity reconstruction of actual operating scenarios. The research systematically investigates how different spalling types and dimensional parameters affect the system’s dynamic behavior. Numerical results demonstrate a positive correlation between the severity of the spalling defect and the dynamic response intensity. Specifically, the expansion of defect dimensions under harsh operating regimes markedly exacerbates both the contact impulses at the needle-roller interface and the overall vibration acceleration amplitudes. Notably, the amplitude increment of the needle rollers is far more pronounced than that of other components. These findings enrich the theoretical understanding of fault-induced dynamic responses in planetary gear systems and provide a solid theoretical and model-based foundation for optimizing the fault diagnosis, condition monitoring, and maintenance strategies of the associated needle roller bearings.