Simulation of journal bearing friction in severe mixed lubrication – Validation and effect of surface smoothing due to running-in

The Stribeck curve has become a common tool used to assess friction benefits. It has been used previously by various researchers and has yielded positive knowledge relating to bearing design and lubrication properties. Results obtained from Stribeck curves provide a solid base to validating simulation approach.

Various simulation approaches have been used to describe lubricated contacts in journal bearings but their levels of detail differ. Simulation approaches have also been considered in cases of metal-metal contact in journal bearings as it is common that single asperities interaction between contacting surfaces occur in lubrication regime which has impact on journal bearing performance. However, little research has been conducted on journal bearing friction in severe mixed lubrication coupled with verification of the calculated results with measurement results.

David Sander and colleagues presented a study which was published in the journal, Tribology International. The study focused on frictional behavior of journal bearings operating from hydrodynamic to mixed lubrication regime where severe metal-metal occurs. The authors used the measurement results obtained on the journal bearing test rig at KS Gleitlager performed with two different static loads acting on the bearings to validate the isothermal elastohydrodynamic simulation approach.

The authors used a fully formulated low viscous 0W20 hydrocarbon engine oil which is currently available on the automotive market. With provision of its density and viscosity at various conditions, the piezoviscous and non-Newtonian behavior of the lubricant was also considered.

Comparison of the friction torque between test measurements and isothermal mixed elastohydrodynamic simulation approach developed in this study were in good agreement in the hydrodynamic and mixed lubrication regime.

Notably, this publication is the result of a long term research project carried out at the Virtual Vehicle Research Center in cooperation with KS Gleitlager GmbH, AVL LIST GmbH, OMV AG and the Institute of Tribology and Energy Conversion Machinery at TU Clausthal. The different backgrounds of the project partners made this project unique in its application and allow for necessary analyses of the complex interactions in a journal bearing system.

The Virtual Vehicle Research Center is an internationally operating research center located in Graz (Styria, Austria) that develops technologies for affordable, safe and environmentally friendly vehicles for road and rail transportation. With over 200 employees, we collaborate with more than 100 domestic and international partners from science and industry sectors. The goal of the center is to create a strong, permanent bridge between university research and industrial development and to foster essential innovation for industry. By participating in numerous national and international projects, the company has established itself as a key research partner.