Friction torque experiment on double-row angular contact bearings with fixed-position preload in vacuum

Purpose Frictional torque is a critical parameter in evaluating the dynamic performance of space-grade angular contact ball bearings. Under extreme vacuum conditions, the frictional torque characteristics of these bearings are significantly altered, resulting in diminished motion accuracy, reduced operational lifespan and potential system failure. This study aims to explore the evolution of frictional torque in double-row angular contact ball bearings subjected to axial preload in vacuum environments. Design/methodology/approach This investigation uses a custom-designed bearing test platform integrated with a high-fidelity electromechanical transmission system for space–environment simulation. This integrated setup enables comprehensive characterization of vacuum effects on friction torque across representative variations in ambient temperature, axial preload and rotational speed. Concurrently, a numerical simulation model for quantitative friction torque prediction is developed. Findings Findings show that while frictional torque rises with increasing axial preload in low-speed angular contact ball bearings, it reaches a plateau once the preload surpasses 5,000 N, with experimental and simulation results showing a 5.83% comprehensive error. Originality/value This study identifies the optimal preload for the stable operation of space-grade angular contact bearings in extreme vacuum environments, providing critical experimental data to support the long-life design of high-precision aerospace mechanisms. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2025-0160/