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Research Papers: Elastohydrodynamic Lubrication

# Some Criteria for Coating Effectiveness in Heavily Loaded Line Elastohydrodynamically Lubricated Contacts—Part I: Dry Contacts

[+] Author and Article Information
Ilya I. Kudish

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

Sergey S. Volkov, Andrey S. Vasiliev, Sergey M. Aizikovich

Composite Materials,
Research and Education Center “Materials,”
Don State Technical University,
Rostov-on-Don 344000, Russia

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received January 26, 2015; final manuscript received June 18, 2015; published online October 30, 2015. Assoc. Editor: Dong Zhu.

J. Tribol 138(2), 021504 (Oct 30, 2015) (10 pages) Paper No: TRIB-15-1026; doi: 10.1115/1.4030956 History: Received January 26, 2015

## Abstract

Contacts of indentors with functionally graded elastic solids may produce pressures significantly different from the results obtained for homogeneous elastic materials (Hertzian results). It is even more so for heavily loaded line elastohydrodynamically lubricated (EHL) contacts. The goal of the paper is to indicate two distinct ways the functionally graded elastic materials may alter the classic results for the heavily loaded line EHL contacts. Namely, besides pressure the other two main characteristics which are influenced by the nonuniformity of the elastic properties of the contact materials are lubrication film thickness and frictional stress/friction force produced by lubricant flow. The approach used for analyzing the influence of functionally graded elastic materials on parameters of heavily loaded line EHL contacts is based on the asymptotic methods earlier developed by authors (Kudish, 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman & Hall/CRC Press, New York; Kudish and Covitch, 2010, Modeling and Analytical Methods in Tribology, Chapman & Hall/CRC Press, New York; and Aizikovich et al., 2006, Contact Problems of Elasticity for Functionally Graded Materials, Fizmatlit, Moscow, Russia). More specifically, it is based on the analysis of contact problems for dry contacts of functionally graded elastic solids and the lubrication mechanisms in the inlet and exit zones as well as in the central region of heavily lubricated contacts.

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## Figures

Fig. 1

Graphs of contact half-width a0s versus relative coating thickness λs for contacts characterized by different ratios of the elastic modules of the coating and substrate β = E'(0)/E'(H)

Fig. 4

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for hard coatings with β = 0.01 and some large and intermediate coating thicknesses λs.

Fig. 5

Graphs of pressure distributions p0s(xs) and phom(xs) versus xs. The graphs are presented for hard coatings with β = 0.01 and some intermediate coating thicknesses λs.

Fig. 2

Graphs of parameter N0s versus relative coating thickness λs for contacts characterized by different ratios of the elastic modules of the coating and substrate β

Fig. 3

Graphs of parameter N0ca0c = β1/4N0sa0s versus relative coating thickness λs for contacts characterized by different ratios of the elastic modules of the coating and substrate β

Fig. 6

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for hard coatings with β = 0.01 and some intermediate coating thicknesses λs.

Fig. 7

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for hard coatings with β = 0.01 and some intermediate and small coating thicknesses λs.

Fig. 8

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for hard coatings with β = 0.1 and some intermediate and small coating thicknesses λs.

Fig. 9

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for hard coatings with β = 0.01 and some small coating thicknesses λs.

Fig. 10

Graphs of pressure p0s(0) in the center of the contact. The graphs are presented for hard and soft coatings (for different values of β) versus coating thickness λs.

Fig. 11

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for soft coatings with β = 100 and some intermediate and small coating thicknesses λs.

Fig. 12

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for soft coatings with β = 10 and some intermediate and small coating thicknesses λs.

Fig. 13

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for soft coatings with β = 100 and some small coating thicknesses λs.

Fig. 14

Graphs of pressure distribution p0s(xs) versus xs. The graphs are presented for soft coatings with β = 10 and some small coating thicknesses λs.

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