Impact of high pressure and shear thinning on journal bearing friction

For the study of mixed lubrication in journal bearings, this paper employs a combined experimental and simulative approach. Extensive measurements on a journal bearing test rig with a low viscosity 0W20 multi-grade lubricant provide a solid basis which is complemented by experimental lubricant data that is measured under high pressure and high shear rates. In this paper, this data is used to investigate the impact of the piezoviscous effect and the non-Newtonian lubricant properties on the friction power losses in journal bearings over a wide range of dynamic loads and shaft speeds.

In particular, this work seeks to predict the friction power losses for journal bearings under both moderate (50 MPa peak load) and high dynamic loads (100 MPa peak load) using the recently presented accurate numerical method (Allmaier et al., 2011 [1], Allmaier et al., 2013 [2]). From the direct comparison to the experimental data a key finding is that the simulation conforms very closely to the measured data. To be more exact, the agreement lies within the measurement uncertainty.

Following this result, the influence of the often neglected piezoviscous effect and the non-Newtonian lubricant rheology is investigated. We conclude that both the piezoviscous effect and the non-Newtonian behaviour are essential to describe the lubrication with multi-grade lubricants in journal bearings. Only the consideration of both properties describes the experimental data very accurately over the entire range of operating conditions studied.