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Research Papers: Elastohydrodynamic Lubrication

Numerical Analysis of Transient Elastohydrodynamic Lubrication During Startup and Shutdown Processes

[+] Author and Article Information
Xiqun Lu, Bin Zhao

College of Power and Energy Engineering,
Harbin Engineering University,
145 Nantong Street,
Nangang District,
Harbin 150001, Heilongjiang, China

Qingbing Dong

College of Power and Energy Engineering,
Harbin Engineering University,
145 Nantong Street,
Nangang District,
Harbin 150001, Heilongjiang, China
e-mail: dongqingbing@hrbeu.edu.cn

Kun Zhou, Bo Zhao

School of Mechanical and
Aerospace Engineering,
Nanyang Technological University,
50 Nanyang Avenue,
Singapore 639798

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received October 15, 2017; final manuscript received January 24, 2018; published online March 30, 2018. Assoc. Editor: Liming Chang.

J. Tribol 140(4), 041504 (Mar 30, 2018) (14 pages) Paper No: TRIB-17-1387; doi: 10.1115/1.4039371 History: Received October 15, 2017; Revised January 24, 2018

In this study, a numerical model is developed for the analysis of elastohydrodynamic lubrication (EHL) at transient conditions during startup and shutdown processes. The time-dependent solutions are derived from an iterative algorithm with surface roughness involved, and the initial value is specified as the solution of the dry contact for the startup or steady-state solution of the lubrication contact at the starting velocity for the shutdown. The technique of discrete convolution and fast Fourier transform (DC-FFT) is employed to improve the computational efficiency. Solutions for smooth surfaces are compared with those obtained numerically and experimentally, and good consistency can be found. Profiles of pressure and film thickness and contours of subsurface stresses are analyzed to reveal the effects of acceleration/deceleration on the lubrication evolution. An isotropic roughness is then taken into account for the analysis. It is concluded that the coupling effects of the lubricant cavitation and oriented roughness would result in complex profiles of pressure and film thickness due to their disturbances to the lubrication film. A machined rough surface is presented to demonstrate the generality of the model. The analysis may potentially provide guidance to estimate the behavior of mechanical elements.

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Figures

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Fig. 1

Flowchart of the computational process

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Fig. 2

Solution comparison of (a) pressure and (b) film thickness by the present model with those by Popovici et al. [34]

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Fig. 3

Pressure distribution and film thickness along x-axis and subsurface von Mises stress contour on the x-z plane at t = (a) 0 ms, (b) 0.5 ms, (c) 1.0 ms, and (d) 1.5 ms

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Fig. 4

Film thickness contours and profiles at u = (a) 0.0024, (b) 0.0043, and (c) 0.0059 m/s

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Fig. 5

Comparison of (a) pressure and film thickness profiles along the x-axis (solid line) and y-axis (dashed line) from the present model and (b) that by Zhao and Sadeghi [20] at t = 0 ms, 2 ms, and 400 ms

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Fig. 6

Dependence of time for (a) central and (b) minimum film thickness at different decelerations a

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Fig. 7

Film thickness profiles during velocity deceleration process at a rate a = (a) −5 m/s2 and (b) −50 m/s2

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Fig. 8

Pressure distribution and film thickness along the x-axis and subsurface von Mises stress contour on the x-z plane at t = (a) 0 ms, (b) 20 ms, (c) 40 ms, and (d) 40 s

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Fig. 9

Pressure distribution and film thickness along x-axis and subsurface von Mises stress contour on the x-z plane at t = (a) 0 ms, (b) 0.1 ms, (c) 0.2 ms, and (d) 0.3 ms

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Fig. 10

Film thickness contours t = (a) 0.5 ms, (b) 0.6 ms, and (c) 0.7 ms after a sudden shutdown process

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Fig. 11

The changes of (a) central and (b) minimum film thickness for startup process

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Fig. 12

(a) Dimensionless surface roughness and film thickness contours at t = (b) 0 ms, (c) 0.3 ms, and (d) 0.7 ms

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