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Research Papers: Elastohydrodynamic Lubrication

Analysis of Soft-Elastohydrodynamic Lubrication Line Contacts on Finite Thickness

[+] Author and Article Information
Qie-Da Chen

Department of Materials
Science and Engineering,
Institute of Nanotechnology and
Microsystems Engineering,
National Cheng Kung University,
No. 1 University Road,
Tainan 701, Taiwan

Wang-Long Li

Professor
Department of Materials
Science and Engineering,
Institute of Nanotechnology and
Microsystems Engineering,
National Cheng Kung University,
No. 1 University Road,
Tainan 701, Taiwan
e-mail: wlli@mail.ncku.edu.tw

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received April 5, 2017; final manuscript received December 3, 2017; published online March 2, 2018. Assoc. Editor: Liming Chang.

J. Tribol 140(4), 041502 (Mar 02, 2018) (8 pages) Paper No: TRIB-17-1126; doi: 10.1115/1.4039161 History: Received April 05, 2017; Revised December 03, 2017

Soft elastohydrodynamic lubrication (soft-EHL) is an important mechanism in biotribological systems. The soft-EHL has some distinct differences from the traditional hard-EHL, and a systematic analysis factoring in key features of the “softness” appears to be lacking. In this paper, a complete soft-EHL line-contact model is developed. In the model, the half-space approximation is replaced by the finite thickness analysis; the geometrical and material nonlinearity due to finite deformation is factored in; the surface velocities altered by the curvature effect are considered, and the load balance equation is formulated based on the deformed configuration. Solutions are obtained using a finite element method (FEM). The film thickness, pressure distributions, and material deformation are analyzed and discussed under various entraining velocities, elastic modulus, and material thickness of the soft layer. Comparisons are made between soft-EHL and hard-EHL modeling assumptions. The analyses show that the classical EHL modeling is not suitable for soft materials with high loads. The results show that the finite deformation (Green strain) should be considered in soft-EHL analysis. In the contact region, the hard EHL solver overestimates the pressure distribution and underestimates the film thickness and deformation.

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Figures

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Fig. 2

Computational domain and deformed configurations

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Fig. 3

Mesh and geometry size

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Fig. 1

Schematic of the soft-EHL line contact

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Fig. 4

Comparison of results obtained by Moghani et al. [10] and those using the present method

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Fig. 5

Hydrodynamic pressure, p and film thickness, h corresponding to case A (hard-EHL), case B, and finite deformation of case C

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Fig. 16

Hydrodynamic pressure, p and film thickness, and h corresponding to different angular velocities

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Fig. 17

The displacement distributions, uz, corresponding to different angular velocities

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Fig. 6

The displacement distributions, uz corresponding to case A, case B, and finite deformation of case C

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Fig. 7

Hydrodynamic pressure, p and film thickness, h corresponding to case C, case D, and soft-EHL of case E

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Fig. 8

The displacement distributions, uz corresponding to case C, case D, and soft-EHL of case E

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Fig. 9

Hydrodynamic pressure, p and film thickness, h corresponding to different thicknesses of the computational domain

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Fig. 10

The displacement distributions, uz corresponding to different thicknesses of the computational domain

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Fig. 11

Central pressure, minimum film thickness, maximum von Mises stress, and deformations corresponding to different loads

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Fig. 12

The displacement distributions, uz and von Mises stress, σvon corresponding to different loads: (a) wL=0.21 N/m, (b) wL=1.05 N/m, and (c) wL=2.1 N/m

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Fig. 13

The maximum pressure corresponding to different loads and elastic moduli

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Fig. 14

The minimum film thickness corresponding to different loads and elastic moduli

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Fig. 15

The maximum deformation corresponding to different loads and elastic moduli

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