Technical Brief

Friction Reduction Effect of Soft Coatings

[+] Author and Article Information
Zhou Chen

Department of Mechanical Engineering,
Haifa 3200003, Israel
e-mail: chenzhou@campus.technion.ac.il

Contributed by the Tribology Division of ASME for publication in the Journal of Tribology. Manuscript received May 27, 2019; final manuscript received July 14, 2019; published online July 31, 2019. Assoc. Editor: Longqiu Li.

J. Tribol 141(10), (Jul 31, 2019) (3 pages) Paper No: TRIB-19-1223; doi: 10.1115/1.4044299 History: Received May 27, 2019; Accepted July 14, 2019

Finite element analysis is conducted on an elastic-plastic full stick contact between a rigid flat and a deformable coated sphere with a soft coating. A combined normal and tangential load is applied to the rigid flat, and the sliding inception is assumed as a result of the decreasing tangential stiffness of the contact junction. As the coating becomes thicker, the static friction coefficient first decreases reaching a minimum and then increases. This demonstrates a friction reduction effect of soft coatings that is opposite to hard coatings. The static friction coefficient decreases with increasing normal load as the contact junction contains more plasticity and becomes more compliant.

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Grahic Jump Location
Fig. 1

A coated sphere in contact with a rigid flat, to which a normal load P with a subsequent tangential displacement ux is applied (adapted from Ref. [11])

Grahic Jump Location
Fig. 2

The variation of the static friction coefficient µ with the dimensionless coating thickness t/R for Eco/Esu = 4, Yco/Ysu = 4, Esu/Ysu = 1000, and P/(EsuR2 × 10−7) = 50 (adapted from Ref. [11])

Grahic Jump Location
Fig. 3

The variation of the static friction coefficient µ with the dimensionless coating thickness t/R for Eco/Esu = 0.5, Yco/Ysu = 0.5, Esu/Ysu = 1000, and P/Lc_co = 100

Grahic Jump Location
Fig. 4

The variation of the static friction coefficient µ with the dimensionless coating thickness t/R for P/Lc_co = 50, 100, 200 when Eco/Esu = 0.5, Yco/Ysu = 0.5, and Esu/Ysu = 1000



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