Heat Partition in Rolling/Sliding Elastohydrodynamic Contacts

[+] Author and Article Information
A. Clarke, K. J. Sharif, H. P. Evans

 Cardiff School of Engineering, The Parade, Cardiff CF24 0YF, United Kingdom

R. W. Snidle1

 Cardiff School of Engineering, The Parade, Cardiff CF24 0YF, United Kingdom


Corresponding author.

J. Tribol 128(1), 67-78 (Jul 19, 2005) (12 pages) doi:10.1115/1.2125867 History: Received February 25, 2004; Revised July 19, 2005

The paper presents the results of a thermal analysis of a set of disk experiments carried out by Patching to investigate scuffing. The experiments used crowned steel disks at 76-mm centers with maximum Hertzian contact pressures of up to 1.7 GPa. Experimental measurements of contact friction were used as the basis for a thermal analysis of the disks and their associated support shafts. Temperatures measured by embedded thermocouples 3.2 mm below the running tracks of the disks were used to determine the heat partition between the faster and slower running disks in order to match the experimental with calculated temperatures. This partition was found to vary approximately as a function of the product of sliding speed and surface temperature difference. A transient (flash) temperature analysis of one of the experiments was also carried out. This shows large differences between the disk transient surface temperatures. These surface temperature distributions were compared with those obtained from corresponding elastohydrodynamic lubrication (EHL) analyses using two different non-Newtonian lubricant formulations. The EHL analyses show that the heat partition obtained depends on the form of non-Newtonian behavior assumed, and that to achieve the same partition as is evident in the experiment a limiting shear stress formulation is necessary. It is suggested that the combination of heat transfer and EHL analysis presented in the paper could be used as a sensitive tool for distinguishing between different non-Newtonian lubricant models under realistic engineering loads and with high sliding speeds.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Test head of disk machine. Fast disk shaft is supported in fixed bearings. Slow disk bearings are supported in a swinging yoke to allow load to be applied to the elliptical contact area.

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Figure 2

Outline drawing of disks and shafts showing simplified shaft geometry (broken lines) used to model (a) the faster running shaft and (b) the slower running shaft

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Figure 3

Final six load stages from chart record of experiment 2-2 showing temperature measurement of fast and slow disks and the corresponding friction measurement F

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Figure 4

Disk and shaft outline used for generating the plane model

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Figure 5

Outer annular region of disk used for flash temperature analysis illustrated in r,θ,z coordinates. Rectangle shown on outer radial surface r=r2 indicates extent of fine mesh at the highest load and hatched rectangle indicates the corresponding contact mesh area. Note that in this representation circumferential distance is foreshortened by a factor of 3 and the true aspect ratio of the contact mesh area shown is 0.83:1.

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Figure 6

Heat transfer factors used in Eqs. 8,9 for surfaces BC and DC (see Fig. 4). Triangles give factors for Eq. 8, circles those for Eq. 9. Solid symbols slow shaft, open symbols fast shaft. Lines show the values (0.2 and 0.106, respectively) given in the equations.

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Figure 7

Results of transient analysis of test 2-2 showing the calculated running track and thermocouple position temperatures for the disks and the assumed friction force taken from Fig. 3, adjusted for bearing friction

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Figure 8

Temperature contours for (a) fast and (b) slow shafts at the end of the last complete load stage prior to scuffing for test 2-2, at t=1080s. To the right are detailed contours for the disks near their outer boundaries.

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Figure 9

(a) Axial and (b) radial temperature profiles for the two disks at time t=1080s for test 2-2, i.e., at the end of the final complete load stage prior to scuffing

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Figure 10

Variation of heat partition parameter, β, with product of surface temperature difference between disks and sliding velocity, ΔTus

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Figure 11

Circumferential variation of surface temperature on the center line of the fast and slow disks at time t=1080s. Maximum slow disk temperature is 199°C.

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Figure 12

Calculated disk center line contact temperatures in experiment 2-2 for the fast and slow disks at time t=1080s. Also shown are the surface frictional heat flux distributions.

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Figure 13

Contours of calculated disk contact temperatures in experiment 2-2 for (a) fast and (b) slow disk at time t=1080s

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Figure 14

Center line mid oil film and surface temperature profiles from EHL analysis using Eyring-type rheological model: Also shown is the calculated heat flux at each surface

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Figure 15

Center line mid oil film and surface temperature profiles from EHL analysis using limiting shear stress rheological model with Barus viscosity. Also shown is the maximum temperature obtained within the film and the calculated heat flux at each surface.



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