Mixed elastohydrodynamic lubrication analysis of roller-race contacts in tunnel boring machine main bearings

The main bearing is essential for ensuring the service life and functional reliability of tunnel boring machines. This work develops a fully coupled mixed elastohydrodynamic lubrication-friction model, accelerated via a parallel finite-element strategy that improves computational efficiency by up to 90%, and validated against experimental roller-race contact data. The model incorporates contact analyses across bearing rows and accounts for both boundary and viscous friction components to comprehensively assess friction force and torque. Results indicate that the logarithmic roller profile enhances lubrication performance. Notably, under high-load conditions where lubricant shear stress reaches its limit, increasing viscosity leads to a slight reduction in axial friction force. Employing a high-viscosity lubricant (Viscosity Grade 680) reduces total friction torque by 4.26%, along with a 4.24% decrease in overall frictional power loss, indicating meaningful efficiency improvements.