Details
| Original language | English |
|---|---|
| Pages (from-to) | 481-500 |
| Number of pages | 20 |
| Journal | Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology |
| Volume | 226 |
| Issue number | 6 |
| Publication status | Published - Jun 2012 |
Abstract
The correct prediction of shear stresses in lubricants applied to concentrated rolling/sliding contacts has been an issue of intense debate for many years. Traction testers of various kinds such as two-disc roller rigs or ball on disc apparatus have been extensively used in order to obtain experimental data, as well as, more recently, molecular dynamics simulations. Several, partly competing, phenomenological models have been developed to describe the dependence of shear stresses on various parameters. Evidently, the importance lies in the need to predict and reduce friction, or, more accurately, resistance to motion of rolling element bearings in order to increase efficiency of machines and vehicles. Also, it plays a crucial role in design and performance of traction drives. As a prerequisite, experimental data for a wide variety of fluids were obtained from two-disc roller tests with a wide variation of contact pressures, rolling speeds and slide-to-roll ratios. Following earlier investigations, the amount of slip created by the elastic deformation of the discs was separated from the contribution of the fluids and their rheological properties. In accordance with experiments of Jacobson a threshold pressure in the fluid was identified which marks the onset of a nearly linear relationship between a limiting shear stress and pressure. However, this threshold does not appear to be constant but rather declining with decreasing hydrodynamic film thickness respective of rolling speed, while the slope changes to a lesser extent. When measurements were extended far into the mixed lubrication regime close to the limiting case of boundary lubrication, the shear stress/pressure relationship became quasi-Coulomb with a virtually zero threshold pressure. These results have successfully been used to predict the friction torque of angular contact ball bearings and the traction characteristics in toroidal drives.
Keywords
- limiting shear stress, Lubricant rheology, rolling contacts, traction-creep relationship, viscoelasticity
ASJC Scopus subject areas
- Engineering(all)
- Mechanical Engineering
- Physics and Astronomy(all)
- Surfaces and Interfaces
- Materials Science(all)
- Surfaces, Coatings and Films
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In: Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Vol. 226, No. 6, 06.2012, p. 481-500.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Fluid rheology, traction/creep relationships and friction in machine elements with rolling contacts
AU - Poll, G. W.G.
AU - Wang, Ding
N1 - Funding Information: This study was supported in part by the Arbeitsgemeinschaft industrieller Forschungsvereinigungen ‘Otto von Guericke’ e.V. (AiF) and by the Forschungsvereinigung Antriebstechnik e.V. (FVA).
PY - 2012/6
Y1 - 2012/6
N2 - The correct prediction of shear stresses in lubricants applied to concentrated rolling/sliding contacts has been an issue of intense debate for many years. Traction testers of various kinds such as two-disc roller rigs or ball on disc apparatus have been extensively used in order to obtain experimental data, as well as, more recently, molecular dynamics simulations. Several, partly competing, phenomenological models have been developed to describe the dependence of shear stresses on various parameters. Evidently, the importance lies in the need to predict and reduce friction, or, more accurately, resistance to motion of rolling element bearings in order to increase efficiency of machines and vehicles. Also, it plays a crucial role in design and performance of traction drives. As a prerequisite, experimental data for a wide variety of fluids were obtained from two-disc roller tests with a wide variation of contact pressures, rolling speeds and slide-to-roll ratios. Following earlier investigations, the amount of slip created by the elastic deformation of the discs was separated from the contribution of the fluids and their rheological properties. In accordance with experiments of Jacobson a threshold pressure in the fluid was identified which marks the onset of a nearly linear relationship between a limiting shear stress and pressure. However, this threshold does not appear to be constant but rather declining with decreasing hydrodynamic film thickness respective of rolling speed, while the slope changes to a lesser extent. When measurements were extended far into the mixed lubrication regime close to the limiting case of boundary lubrication, the shear stress/pressure relationship became quasi-Coulomb with a virtually zero threshold pressure. These results have successfully been used to predict the friction torque of angular contact ball bearings and the traction characteristics in toroidal drives.
AB - The correct prediction of shear stresses in lubricants applied to concentrated rolling/sliding contacts has been an issue of intense debate for many years. Traction testers of various kinds such as two-disc roller rigs or ball on disc apparatus have been extensively used in order to obtain experimental data, as well as, more recently, molecular dynamics simulations. Several, partly competing, phenomenological models have been developed to describe the dependence of shear stresses on various parameters. Evidently, the importance lies in the need to predict and reduce friction, or, more accurately, resistance to motion of rolling element bearings in order to increase efficiency of machines and vehicles. Also, it plays a crucial role in design and performance of traction drives. As a prerequisite, experimental data for a wide variety of fluids were obtained from two-disc roller tests with a wide variation of contact pressures, rolling speeds and slide-to-roll ratios. Following earlier investigations, the amount of slip created by the elastic deformation of the discs was separated from the contribution of the fluids and their rheological properties. In accordance with experiments of Jacobson a threshold pressure in the fluid was identified which marks the onset of a nearly linear relationship between a limiting shear stress and pressure. However, this threshold does not appear to be constant but rather declining with decreasing hydrodynamic film thickness respective of rolling speed, while the slope changes to a lesser extent. When measurements were extended far into the mixed lubrication regime close to the limiting case of boundary lubrication, the shear stress/pressure relationship became quasi-Coulomb with a virtually zero threshold pressure. These results have successfully been used to predict the friction torque of angular contact ball bearings and the traction characteristics in toroidal drives.
KW - limiting shear stress
KW - Lubricant rheology
KW - rolling contacts
KW - traction-creep relationship
KW - viscoelasticity
UR - http://www.scopus.com/inward/record.url?scp=84864452598&partnerID=8YFLogxK
U2 - 10.1177/1350650111431790
DO - 10.1177/1350650111431790
M3 - Article
AN - SCOPUS:84864452598
VL - 226
SP - 481
EP - 500
JO - Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology
JF - Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology
SN - 1350-6501
IS - 6
ER -