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TECHNICAL PAPERS

Granular Collision Lubrication: Experimental Investigation and Comparison to Theory

[+] Author and Article Information
Karim N. Elkholy

Department of Mechanical Engineering,  Louisiana State University, 2508 CEBA, Baton Rouge, LA 70803

M. M. Khonsari1

Department of Mechanical Engineering,  Louisiana State University, 2508 CEBA, Baton Rouge, LA 70803khonsari@me.lsu.edu

1

Corresponding author.

J. Tribol 129(4), 923-932 (May 25, 2007) (10 pages) doi:10.1115/1.2768613 History: Received April 01, 2007; Revised May 25, 2007

An experimental investigation of the friction and lift characteristics of granular lubrication is presented. Experiments are carried out to demonstrate the vertical displacement (lift) observed in an annular shear cell apparatus. Results are presented for the friction coefficient as a function of the rotational speed and the applied load for several surface roughness combinations. Simulations of the kinetic theory for the granular material are performed and compared to the experimental results. The experiments provide an evidence for the formation of granular lift between two disks undergoing sliding motion.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the experimental apparatus

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Figure 2

Shear cell assembly

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Figure 3

Surface roughness: (a) wire mesh and (b) steel balls glued to the surface using the wire mesh

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Figure 4

Effect of the rotational speed on the friction coefficient (Series A: Both the sliding and stationary disks are rough)

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Figure 5

Effect of the rotational speed on the vertical displacement (Series A: Both the sliding and stationary disks are rough)

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Figure 6

Effect of the normal load on the friction coefficient (Series A: Both the sliding and stationary disks are rough)

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Figure 7

Effect of the normal load on the vertical displacement (Series A: Both the sliding and stationary disks are rough)

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Figure 8

Effect of the normal load on the friction coefficient (Series B: Rough sliding surface and smooth stationary disk)

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Figure 9

Effect of the normal load on the displacement (Series B: Rough sliding surface and smooth stationary disk)

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Figure 10

Effect of the normal load on the friction coefficient (Series C: Smooth sliding surface and rough stationary disk)

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Figure 11

Effect of the normal load on the displacement (Series C: Smooth sliding surface and rough stationary disk)

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Figure 12

Upper disk roughness using CNC machine

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Figure 13

Effect of the normal load and rotational speed on the friction coefficient (Series D: Rough indents sliding surface and smooth stationary disk)

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Figure 14

Effect of the normal load and rotational speed on the displacement (Series D: Rough indents sliding surface and smooth stationary disk)

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Figure 15

Schematic of the granular lubricant sheared between two parallel plates

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Figure 16

Velocity, temperature, and solid fraction distribution for granular material sheared between two parallel plates (in dimensionless form)

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Figure 17

Variation of the friction coefficient with speed at 7.8kPa (Series A: Rough sliding surface and rough stationary disk)

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Figure 18

Variation in the gap dilation with speed at 7.8kPa (Series A: Rough sliding surface and rough stationary disk)

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Figure 19

Effect of the normal load on the variation in the gap dilation (Series A: Rough sliding surface and rough stationary disk)

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Figure 20

Variation of the shear stress and normal stress with the shear rate (Series A: Rough sliding surface and rough stationary disk)

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Figure 21

Variation of the shear stress with the normal stress (Series A: Rough sliding surface and rough stationary disk)

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