The response of thermal Newtonian and non-Newtonian EHL to the vertical vibration of a roller

Liu, F; Yang, Peiran; Zhang, Jin; Dowson, D.

doi:10.1016/s0167-8922(03)80046-9

Cited by 6 publications

(10 citation statements)

References 16 publications

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“…There are only a limited number of studies where both thermal and transient effects have been considered, but only under relatively lightly loaded conditions [8,9]. Recently, more realistic operating conditions have been incorporated by the present authors in a combined thermal and transient EHL analysis of line contacts under either vertical [10] or longitudinal [11] vibrations. However, the effect of the combined vertical and longitudinal vibrations on EHL has not been studied in the literature.…”

Section: Introductionmentioning

confidence: 99%

On the time-dependent, thermal and non-Newtonian elastohydrodynamic lubrication of line contacts subjected to normal and tangential vibrations

Yang

Jin

Liu

et al. 2004

Proceedings of the Institution of Mechanical Engineers, Part J:

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Complete numerical solutions were obtained for the time-dependent thermal elastohydrodynamic lubrication (EHL) of line contacts under combined vertical and longitudinal vibrations. It was assumed that the contact was composed of two in®nitely long steel rollers. These rollers were then simpli®ed as an in®nite plane and an equivalent roller. The lubricant was assumed to be a Ree±Eyring non-Newtonian¯uid. The time-dependent numerical solutions were achieved instant after instant in each period of vibrations. The periodic error was checked at each end of the vibration period until the responses of pressure, ®lm thickness and temperature were all periodic functions with the frequency of the roller's vibrations. At each instant, the pressure ®eld was solved with a multi-grid method, the surface deformation was solved with a multi-level multi-integration technique, and the temperature ®eld was solved with a ®nite difference scheme through a sweeping process. It was shown that the normal vibration dominated the EHL characteristics and could be either strengthened or weakened slightly depending on the phase of the tangential vibration. It was also found that the vibration of the roller could produce transient surface dimples within the contact conjunction.

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Section: Introductionmentioning

confidence: 99%

On the time-dependent, thermal and non-Newtonian elastohydrodynamic lubrication of line contacts subjected to normal and tangential vibrations

Yang

Jin

Liu

et al. 2004

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…The squeeze film phenomenon has been attributed to thermal wedge effect in sliding contacts by Liu et al. 35 In their case any change in the sliding velocity (Couette flow can be viewed as yielding an equivalent change in the squeeze film as: 35 Udρhdx=dxdtdρhdx=dρhdt (see equation (6)). This is in line with squeeze cave behaviour in Figure 10 and the observations in Kushwaha and Rahnejat 8 that formation of the cave is because of contact kinematics (including the effect of approaching squeeze velocity) even under isothermal conditions as well as any changes in lubricant viscosity due to localised temperature conditions.…”

Section: Resultsmentioning

confidence: 99%

“…is given by equation (35). This total contact reaction, W should equate the instantaneous load share of any contact obtained through dynamic analysis and equation (2).…”

Section: Methods Of Solutionmentioning

confidence: 99%

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Roller bearing dynamics under transient thermal-mixed non-Newtonian elastohydrodynamic regime of lubrication

Mohammadpour

Johns-Rahnejat

Rahnejat

2015

Proceedings of the Institution of Mechanical Engineers, Part K:

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Additional Information:• Abstract:The paper describes a combined tribodynamics analysis (dynamics and contact tribology) of cylindrical roller bearings of a heavy duty truck transmission under high applied loads. The dynamic analysis provides the transient variations in contact load. It also determines the vibration spectrum of the bearing as well as that of contact dynamics. It is shown that with sufficient preloading and/or interference fitting a widely spread loaded region results, which reduces bearing-induced vibration. The transient tribological analysis, including thermal analysis with a novel and realistic lubricant inlet boundary condition demonstrates that nonNewtonian mixed elastohydrodynamic regime of lubrication is prevalent, but with reduced friction compared with unrealistic dry Coulombic friction, which is often assumed in literature.

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“…The presence of a dimple enhances the lubricant film thickness and reduces the chance of direct boundary interactions. Some have attributed this phenomenon to be the result of thermal effect (Liu et al [29]). The results here show reduced magnitude of secondary pressure peak because of a lower rate of change of viscosity in the vicinity of the contact exit in the thermal contact.…”

Section: Resultsmentioning

confidence: 99%

Mixed thermo-elastohydrodynamic cam-tappet power loss in low-speed emission cycles

Chong

Teodorescu

Rahnejat

2012

International Journal of Engine Research

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The key driving forces in engine development are fuel efficiency and emission levels. These aspects are particularly poignant under vehicle idling or low crawling motions in typical city driving. Under these conditions the parasitic frictional losses are exacerbated and the emission levels are especially high. A key engine sub-system is the valve train system. Although it accounts for only 2-3% of the overall engine losses, it is the highest loaded conjunction in the engine, thus limiting the opportunity for lowering the lubricant bulk viscosity. The paper presents detailed tribology of cam-tappet contact, subjected to a mixed thermo-elastohydrodynamic regime of lubrication. In particular, the frictional behaviour of the conjunction is investigated under the stringent North American emission testing city cycle. Such a comprehensive approach has not hitherto been reported in literature. The predictions show good conformance with vehicle frictional assessments in industry. It further demonstrates that under the aforementioned cycle, highest power losses occur which are mainly as the result of lubricant film viscous shear at low sliding speeds and below the lubricant limiting Eyring shear stress.

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The response of thermal Newtonian and non-Newtonian EHL to the vertical vibration of a roller

Cited by 6 publications

References 16 publications

On the time-dependent, thermal and non-Newtonian elastohydrodynamic lubrication of line contacts subjected to normal and tangential vibrations

On the time-dependent, thermal and non-Newtonian elastohydrodynamic lubrication of line contacts subjected to normal and tangential vibrations

Roller bearing dynamics under transient thermal-mixed non-Newtonian elastohydrodynamic regime of lubrication

Mixed thermo-elastohydrodynamic cam-tappet power loss in low-speed emission cycles

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