USCAR Traction Test Methodology for Traction-CVT Fluids

Wedeven, L. D.; Wedeven, G. G.; Kratz, Sascha; King, Tracey; Linden, James L.; Caracciolo, Fabrizio; McWatt, D.G.

doi:10.4271/2002-01-2820

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…Figure 7 shows the measurable contact forces F c and peripheral velocities U with the two-roller traction tester. For comparison, the measurable ranges of the conventional traction testers described in References [1,2] are also shown in the figure. In this figure, Q (= μ max F c U) represents the maximum transmitting power calculated assuming that the value of μ max is 0.1.…”

Section: Configuration Of the Traction Testermentioning

confidence: 99%

“…Conventional traction tester B [2]  The transmittable power : Q =  max UF c  The values of Q is determined assuming that the value of  max is 0.1. The traction curve obtained above becomes asymmetrical about the coordinate origin, as shown in Fig.…”

Section: Kwmentioning

confidence: 99%

“…These models have several parameters identified from measured results of the traction curve. The measured and analyzed results of Several reports show the measured traction curves and discuss the effects of operating parameters (fluid temperature, peripheral velocities, and maximum contact pressures) on the traction characteristic [1][2][3][4][5], and it is verified that the traction characteristic is closely related to the phase diagram of the traction fluid [6][7][8]. Several attempts have been made to quantitatively evaluate the effects of the operating parameters on the traction characteristic using rheological parameters determined through curve fitting with measured traction curves [9,10].…”

Section: Introductionmentioning

confidence: 99%

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Development of a High-Power Two-Roller Traction Tester and Measurement of Traction Curves

et al. 2016

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Measuring and estimating the traction coefficient is necessary to improve transmitting efficiency and design compact, lightweight toroidal continuously variable transmissions (T-CVTs). However, few attempts have been made to measure and estimate the traction coefficient of T-CVTs under practical usage conditions, and the design of T-CVTs has used extrapolated values from traction coefficients measured under low-power conditions. Therefore, we developed a high-power two-roller traction tester to clarify variation trends in traction curves under operating conditions similar to a T-CVT. The results showed a nearly linear relation between the maximum traction coefficient and the roller surface temperature. Furthermore, the change rate of the maximum traction coefficient with respect to roller surface temperature was dependent on the maximum contact pressure. This paper also compares several traction models under practical operating conditions. A viscoelastoplastic model was constructed and compared with a conventional elastoplastic model. In a wide range of operating conditions, the viscoelastoplastic model showed small differences in the maximum traction coefficient between measured and calculated curves compared with the elastoplastic model. The traction tester and the traction model contribute to building a traction curve database to make T-CVTs more compact, lightweight, and efficient.

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Section: Configuration Of the Traction Testermentioning

confidence: 99%

Section: Kwmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Development of a High-Power Two-Roller Traction Tester and Measurement of Traction Curves

et al. 2016

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“…By tilting the disk axis in a twin-disk machine, Poon and Haines [5] and Johnson and Robert [6] introduced spin in a rolling/sliding contact, and the forces transmitted in an angular contact bearing and viscoelastic property of lubricants were investigated, respectively. Some other set-ups were also presented to incorporate spinning motion into rolling/ sliding EHL contacts, for example, Robert and Johnson [7] and Newall and Lee [8] employed the disc-ball-disc configuration, and Wedeven et al [9], a tilted ball axis in a ball-on-disc contact. It is revealed that the effective friction coefficient with lubricated spinning is usually larger than that under rolling/sliding conditions, and the spinning motion plays an important role in the power loss in some lubricated components.…”

Section: Introductionmentioning

confidence: 98%

Interferometry Measurement of Spin Effect on Sliding EHL

Jiang

Guo

et al. 2008

Tribol Lett

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This paper describes interferometry measurement of the film profiles of sliding elastohydrodynamic lubrication (EHL) contacts with spin. In the custom-made EHL test rig, spin motion is introduced through adjusting the center offset of the ball-on-disc contact with respect to the disc rotation axis. A parameter, spin ratio S sp , is employed to represent the spin level, which is defined as the ratio of the Hertzian contact radius to the center offset. Experimental results show that with spin the film shape is obviously skewed, and the film thicknesses at the two side lobes are no longer the same; therefore, the symmetry of the classical horseshoe film shape is lost. The film thickness dependences on entrainment speeds are significantly influenced by the spin ratio S sp , and high spin ratios induce high speed indices. At a fixed spin ratio S sp , with increasing sliding speeds the film thickness difference between the two side lobes becomes large, and the horseshoe film shape is more distorted. When applied loads are raised, more spin is introduced, film thickness decreases, and film shape is obviously twisted.

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“…In gear contacts, mean pressures are typically between 1 and 2 GPa and most research on EHD friction, with one main exception [6], has been made at these pressures. However, there are some machine components, in particular rolling bearings, but also some constant velocity joints [7] and continuously variable transmission components [8] that may operate at significantly higher contact pressures, as indicated in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Measurement of EHD Friction at Very High Contact Pressures

Zhang

Spikes

2020

Tribol Lett

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EHD friction curves have been measured up to very high pressure (p mean = 5 GPa, p max = 7.5 GPa) using a newly developed, rolling-sliding, ball on disc machine, the ETM. Six base fluids have been studied, spanning the API base oil categories Group I to Group V. At high pressures, thermal effects become substantial even at quite modest slide-roll ratios, and these must be considered when analysing friction measurements in terms of the underlying rheological properties of the oils. By comparing measurements from steel/steel and WC/WC ball and disc combinations with very different thermal conductivities, the use of thermal correction to derive isothermal friction curves has been validated. At relatively low pressures (mean pressure = 1 GPa), there are substantial differences between the EHD friction properties of the various API Group base oils, but as pressure is raised these diminish and the EHD friction coefficients of all the Groups approach a similar maximum value at a given temperature. EHD friction continues to be quite strongly temperature dependent even at very high pressure. As pressure is increased, EHD friction curves become progressively steeper, so that friction coefficients at very low slide-roll ratios (1 to 2% SRR) become several times greater at high than at low pressure. This has important practical implications for the efficiency of rolling element bearings at high pressures since these components normally operate in this SRR range. There is no evidence of any of the base oils reaching a limiting shear stress over the whole pressure and temperature range studied. Instead, shear stress continues to increase with log(strain rate) in accord with the Eyring-activated flow model up to very high pressures.

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USCAR Traction Test Methodology for Traction-CVT Fluids

Cited by 6 publications

References 8 publications

Development of a High-Power Two-Roller Traction Tester and Measurement of Traction Curves

Development of a High-Power Two-Roller Traction Tester and Measurement of Traction Curves

Interferometry Measurement of Spin Effect on Sliding EHL

Measurement of EHD Friction at Very High Contact Pressures

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