Determination of Friction Torque in Self-Lubricating Sliding Bearings as a Function of Temperature Data

Abstract

Long-term and safe operation of complex mechanisms and assemblies requires timely diagnostics of frictional units. This work presents results of determining the friction torque in self-lubricating sliding bearings from temperature data. A system of sliding bearings made of a polymer composite material, which support a rotating shaft, was investigated. A mathematical model of the thermal process in the considered system is given, accounting for the spatial distribution of temperature and its temporal variation. Temperature was recorded with thermocouples at several points on each bearing. Friction torque was determined from frictional heat generation using a solution of the inverse heat transfer problem (criterion: agreement between measured and calculated temperatures). Temperature data with measurement errors were processed statistically. Refinement of the inverse problem solution was stopped upon convergence of successive approximations. To ensure continuous data processing and determination of friction torque during long tests, the inverse heat transfer problem was solved on successive short time intervals, and the obtained solutions were then stitched together. It is shown that the discrepancy between values of the total friction torque obtained from temperature-based calculations and from measurements with an inductive sensor does not exceed 15%. The proposed thermal diagnostic method for friction can be used to determine friction torques in self-lubricating sliding bearings in both bench and in-service tests of machine friction units, and to improve the reliability of bearing condition diagnostics.