A Methodology to Measure Power Losses of Rolling Element Bearings under Combined Radial and Axial Loading Conditions

In this study, an experimental methodology is presented for measuring power losses of rolling element bearings under combined radial and axial loading conditions. The setup developed for this purpose consists of a pair of test bearings and another pair of center bearings whose function is to transmit the radial load to the test bearings. The center bearings are isolated from any axial load that is carried by the test bearings. The proposed methodology relies on a family of separate measurements to (1) remove center bearing losses from the losses of the test bearings and (2) separate load-independent (spin) and load-dependent (mechanical) components of power losses of the test bearings. The setup includes a precise lubricant delivery system that controls flow rate and temperature of oil supplied to each test and center bearing individually. Because the bulk temperatures of bearings tested impact the measured power losses significantly, a heat management system is implemented to maintain the bearing bulk temperatures at the same value as the set levels of the oil inlet temperature. The methodology is demonstrated on two deep-groove ball bearings of different sizes, considering wide ranges of axial and radial forces, rotational speed, oil flow rate, and oil inlet temperature (oil viscosity). The influence of bearing bulk temperatures on power loss measurements is demonstrated as well as the repeatability of the proposed methodology. Furthermore, spin and mechanical loss measurements are compared to a widely used calculation method to assess their accuracy.