The geometric homogeneity of rollers, namely the dimension and shape deviations among rollers in a roller bearing, is one of the most important manufacturing errors. However, to the best of the authors’ knowledge, no specified investigation has been carried out on the effects of the geometric homogeneity of rollers on the friction torque of tapered roller bearings (TRBs). By introducing the diameter deviation of rollers and the distribution form of rollers with a diameter deviation, this study presents a mathematic model to reveal the effects of the geometric homogeneity of rollers on the friction torque of TRBs. The geometric homogeneity of the rollers, although having only a minimal influence on the overall friction torque acting on rings, can lead to a significant increase in the slide friction force between the individual rollers and the inner raceway. By comparing the distribution form of rollers with a diameter deviation, the diameter deviation value of the roller shows a significant influence on the maximum sliding friction between the roller and the inner raceway. The impact of the geometric homogeneity of rollers on the sliding friction between the roller and the inner raceway is more pronounced under light load conditions. The above-mentioned comparisons and conclusions can be used in formulating machining error criteria for TRB rollers.

The fault quantification of a tapered roller bearing (TRB) can provide a reliable guide for predictive maintenance. Currently, damage size estimation based on vibration signals has been proposed and developed. However, most approaches are focused on the theory of ball bearings. Unlike the point contact of a ball bearing, the contact between the tapered roller and the raceway is a line contact. So, the current practices based on the micro-motion theory of ball bearings are limited when estimating the TRB’s fault. To accurately estimate the TRB’s damage size, a dynamic model of non-penetrating damaged TRB was established to research the vibration response mechanism and explain the influence. The model takes the deflection factor of a tapered roller into consideration and uses the elastohydrodynamic lubrication model to simulate the influence of the lubrication factor. Then, a revised formula for estimating the TRBs’ fault size is proposed by uncovering the relationship between the impact time and the damage location. Simulation analysis and experimental analysis prove the correctness of the dynamic model and the effectiveness of the size estimation formula.

During the actual operating conditions, it is inevitable that rolling bearings will be subjected to impact loading. However, due to the very short duration of impact loading, previous studies have almost ignored the influence of impact loading on fatigue life of roller bearings. This paper attempts to construct a numerical framework to address the above issues, thereby providing a theoretical basis for predicting fatigue life of roller bearings under frequent impact loading. A quasi-dynamic model of roller bearings is established to capture the instantaneous fluctuation in roller–raceway contact loads due to impact loading. Then, the influence of impact loading on the fatigue life of roller bearings is accurately characterized based on Miner’s rule. The results show that the frequent impact loading causes a significant decrease in the fatigue life of roller bearings, and the extent of fatigue life decrease depends on the bearing speeds and load conditions. To accurately predict the fatigue life of roller bearings under actual operating conditions, it is necessary to account for the influence of the impact loading, especially for high speeds and light load conditions.