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Research Papers: Elastohydrodynamic Lubrication

Revision of a Fundamental Assumption in the Elastohydrodynamic Lubrication Theory and Friction in Heavily Loaded Line Contacts With Notable Sliding

[+] Author and Article Information
Ilya I. Kudish

Professor
Fellow ASME
Department of Mathematics,
Kettering University,
Flint, MI 48504

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received January 27, 2015; final manuscript received May 17, 2015; published online July 23, 2015. Assoc. Editor: Zhong Min Jin.

J. Tribol 138(1), 011501 (Jul 23, 2015) (15 pages) Paper No: TRIB-15-1029; doi: 10.1115/1.4030788 History: Received January 27, 2015

An analysis of the classic friction modeling in lubricated contacts is conducted. Its major deficiency for soft materials (low-elastic moduli) leading to significant overstating of friction in heavily loaded isothermal and thermal lubricated contacts is revealed. An improved model of friction in a heavily loaded lubricated contact is proposed. The model is based on incorporating the tangential displacements of the solid surfaces in contact, leading to a significant reduction of the frictional stress due to the decrease of the actual sliding of lubricated surfaces. Generally, this frictional stress reduction increases with the slide-to-roll ratio, and it is extremely important for high slide-to-roll ratios for which classic approaches lead to unrealistically overestimated values of frictional stresses. The high slide-to-roll ratio values can be found in many practical applications, such as clutches. Several examples of the frictional stress calculated based on this model as well as the comparison with the classical results are given for the case of smooth solid surfaces and lubricants with Newtonian rheology. Also, the results allow to take a look at the role and the necessity of considering thermal and lubricant non-Newtonian effects on solution of various EHL problems for such heavily loaded contacts.

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References

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Jacod, B. , 2002, “Friction in Elasto-Hydrodynamic Lubrication,” Ph.D. thesis, University of Twente, Enschede, The Netherlands.
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Bair, S. , and Winer, W. O. , 1982, “Some Observations in High Pressure Rheology Off Lubricants,” ASME J. Lubr. Technol., 104(3), pp. 357–364. [CrossRef]
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Bair, S. , 2000, “Pressure-Viscosity Behavior of Lubricants to 1.4 GPa and Its Relation to EHD Traction,” STLE Tribol. Trans., 43(1), pp. 91–99. [CrossRef]
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Hoglund, E. , and Jacobson, B. , 1986, “Experimental Investigation of the Shear Strength of Lubricants Subjected to High Pressure and Temperature,” ASME J. Tribol., 108(4), pp. 571–578. [CrossRef]
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Kudish, I. I. , 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches,” Chapman & Hall/CRC Press, Taylor & Francis Group.
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Figures

Grahic Jump Location
Fig. 1

The full-scale view of the actual surface velocity distribution v1(x) of the lower solid obtained for V = 0.1 and different values of Q

Grahic Jump Location
Fig. 2

The magnified view of the actual surface velocity distribution v1(x) of the lower solid obtained for V = 0.1 and different values of Q

Grahic Jump Location
Fig. 3

The full-scale view of the actual surface velocity distribution v2(x) of the upper solid obtained for V = 0.1 and different values of Q

Grahic Jump Location
Fig. 4

The magnified view of the actual surface velocity distribution v2(x) of the upper solid obtained for V = 0.1 and different values of Q

Grahic Jump Location
Fig. 5

The full-scale view of the actual average surface velocity distribution 0.5[v1(x) + v2(x)] obtained for V = 0.1 and different values of Q

Grahic Jump Location
Fig. 6

The magnified view of the actual average surface velocity distribution 0.5[v1(x) + v2(x)] obtained for V = 0.1 and different values of Q

Grahic Jump Location
Fig. 7

The full-scale view of the sliding velocity distribution s(x) obtained for V = 0.1 and different values of Q

Grahic Jump Location
Fig. 8

The magnified view of the sliding velocity distribution s(x) obtained for V = 0.1 and different values of Q

Grahic Jump Location
Fig. 9

The sliding frictional stress f(x) calculated for the case of actual sliding velocity s(x) (solid line) and for the classic case of s(x) = s0 and 0.5[v1(x) + v2(x)] = 1 (line marked by circles) obtained for V = 0.1 and Q = 0

Grahic Jump Location
Fig. 10

The sliding frictional stress f(x) calculated for the case of actual sliding velocity s(x) (solid line) and for the classic case of s(x) = s0 and 0.5[v1(x) + v2(x)] = 1 (line marked by circles) obtained for V = 0.1 and Q = 5

Grahic Jump Location
Fig. 11

The pressure distribution p(x) obtained for V = 0.1 and Q = 5 calculated for the case of actual sliding velocity s(x) (line marked by circles) and for the classic case of s(x) = s0 and [v1(x) + v2(x)]/2 = 1 (solid line)

Grahic Jump Location
Fig. 12

The pressure distribution p(x) obtained for V = 0.1 and Q = 10 calculated for the case of actual sliding velocity s(x) (line marked by circles) and for the classic case of s(x) = s0 and [v1(x) + v2(x)]/2 = 1 (solid line)

Grahic Jump Location
Fig. 13

The gap distribution h(x) obtained for V = 0.1, Q = 5, and Q = 10 calculated for the case of actual sliding velocity s(x) and for the classic case of s(x) = s0 and [v1(x) + v2(x)]/2 = 1 (marked by s = s0)

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