Modeling of Film Thickness and Traction in a Variable Ratio Traction Drive Rig

There is currently considerable debate concerning the most appropriate rheological model to describe the behaviour of lubricant films in rolling-sliding, elastohydrodynamic contacts. This is an important issue since an accurate model is required in to predict friction in such contacts. This paper reviews the origins of this debate, which primarily concerns a divergence of views between researchers using high pressure, high shear rate viscometry and those concerned with the measurement and analysis of elastohydrodynamic friction; the former advocate a Carreau-based shear stress/strain rate model while the latter generally favour an Eyring-based one. The crucial importance of accounting for shear heating effects in analysing both viscometric and friction data is discussed. The main criticisms levied by advocates of a Carreau-based model against Eyring's model are discussed in some detail. Finally the ability of both types of rheological model to fit elastohydrodynamic friction measurements for a quite simple, well-defined base fluid is tested, using previously-measured pressure-viscosity behaviour for the fluid. Both models appear to fit the experimental data over a wide temperature range quite well, though fit of the Eyring model appears slightly closer than that of the Carreau-Yasuda model. Friction data from a wider range of welldefined fluid types is needed to identify categorically the most appropriate model to describe elastohydrodynamic friction.

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“…[46][47][48][49][50][51][52]. All produce, as might be expected, the general shape of traction curves, with varying levels of quantitative match.…”

Section: Variation Of Pressure Across the Contactmentioning

confidence: 99%

History, Origins and Prediction of Elastohydrodynamic Friction

2014

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“…For purely elastohydrodynamic conditions, one would expect a coefficient of friction < 0.05. 34 It also shows that a constant value cannot be assumed with such transient meshing conditions.…”

Section: Resultsmentioning

confidence: 99%

“…Such conditions are prevalent in the case of hypoid gears, which is the subject of the current study. Sharif et al 34 presented a thermal non-Newtonian model to obtain film thickness and traction in a variable traction drive rig. The model was presented for circular point contacts only.…”

Section: Introductionmentioning

confidence: 99%

Non-Newtonian mixed thermo-elastohydrodynamics of hypoid gear pairs

Mohammadpour

Theodossiades

Rahnejat

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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Transmission efficiency is the main objective in the development of vehicular differential systems, comprising hypoid gear pairs. The overall aim is to contribute to improved vehicle fuel efficiency and thus levels of harmful emissions for modern desired eco-drive axles. Detailed predictive analysis plays an important role in this quest, particularly under realistic operating conditions, comprising high contact loads and shear rates. Under these conditions, the hypoid gear pairs are subject to mixed non-Newtonian thermo-elastohydrodynamic conditions, which is the approach undertaken in this paper. Such an approach for hypoid gear pair has not hitherto been reported in the literature.

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“…where θ e is the effective contact temperature and c p is the specific heat capacity of the lubricant, and its mass flow rate is found as [42]:…”

Section: Thermal Network Modelmentioning

confidence: 99%

“…The contact area A EHL is simply 2bl, where b and l are the Hertzian contact width and length, respectively. Moreover, S f i is found as [42]:…”

Section: Thermal Network Modelmentioning

confidence: 99%

Lubricated Loaded Tooth Contact Analysis and Non-Newtonian Thermoelastohydrodynamics of High-Performance Spur Gear Transmission Systems

2020

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Energy efficiency and functional reliability are the two key requirements in the design of high-performance transmissions. Therefore, a representative analysis replicating real operating conditions is essential. This paper presents the thermoelastohydrodynamic lubrication (TEHL) of meshing spur gear teeth of high-performance racing transmission systems, where high generated contact pressures and lubricant shear lead to non-Newtonian traction. The determination of the input contact geometry of meshing pairs as well as contact kinematics are essential steps for representative TEHL. These are incorporated in the current analysis through the use of Lubricated Loaded Tooth Contact Analysis (LLTCA), which is far more realistic than the traditional Tooth Contact Analysis (TCA). In addition, the effects of lubricant and flash surface temperature rise of contacting pairs, leading to the thermal thinning of lubricant, are taken into account using a thermal network model. Furthermore, high-speed contact kinematics lead to shear thinning of the lubricant and reduce the film thickness under non-Newtonian traction. This comprehensive approach based on established TEHL analysis, particularly including the effect of LLTCA on the TEHL of spur gears, has not hitherto been reported in literature.

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Modeling of Film Thickness and Traction in a Variable Ratio Traction Drive Rig

Abstract: The paper describes the application of a full non-Newtonian, thermal elastohydrodynamic lubrication (EHL)

Cited by 33 publications

References 17 publications

History, Origins and Prediction of Elastohydrodynamic Friction

History, Origins and Prediction of Elastohydrodynamic Friction

Non-Newtonian mixed thermo-elastohydrodynamics of hypoid gear pairs

Lubricated Loaded Tooth Contact Analysis and Non-Newtonian Thermoelastohydrodynamics of High-Performance Spur Gear Transmission Systems

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