An investigation for the friction torque of a needle roller bearing with the roundness error

Needle roller bearings (NRBs) are key components in industrial machinery. The rotational accuracy and efficiency of the machinery are determined by the friction torques of their interior NRBs. This study proposes an analytical method for calculating the friction torque of a NRB without and with the roundness error. This model formulates the rolling friction torques produced by the elastic material hysteresis, slipping friction torques generated by differential slipping, viscous friction torques caused by the lubricating oil, slipping torques generated by the slipping between mating components, and centrifugal force of the needle roller. The friction torques of a healthy solid-grease-lubricated NRB calculated by Palmgren's, SKF's, Chiu and Myers's, and proposed methods are compared. The influences of the radial load, inner raceway velocity, and roundness error on the friction torque increment of an unhealthy solid-grease-lubricated NRB are analyzed by using the proposed method. Moreover, the results from Palmgrem's method, SKF's method, Chiu and Myers's method, proposed method, and Iqbal et al.'s experimental investigations are compared to validate the proposed method. It seems that this study can give a more accurate method for predicting the friction torque of the NRB with the roundness error compared to the previous empirical methods.