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TECHNICAL PAPERS

EHL Modeling for Nonhomogeneous Materials: The Effect of Material Inclusions

[+] Author and Article Information
Trevor S. Slack, Nihar Raje, Farshid Sadeghi

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47906

Gary Doll

Tribology, Timken Technology Center, Canton, OH 44706

Michael R. Hoeprich

 Timken Technology Center, Canton, OH 44706

J. Tribol 129(2), 256-273 (Jan 02, 2007) (18 pages) doi:10.1115/1.2540234 History: Received August 25, 2006; Revised January 02, 2007

Inclusions are common in bearing materials and are a primary site for subsurface fatigue crack initiation in rolling element bearings. This paper presents a new approach for computing the pressure, film thickness, and subsurface stresses in an elastohydrodynamic lubrication (EHL) contact when inclusions are present in the elastic half-space. The approach is based on using the discrete element method to determine the surface elastic deformation in the EHL film thickness equation. The model is validated through comparison with the smooth EHL line contact results generated using linear elasticity. Studies are then carried out to investigate the effects of size, location, orientation, and elastic properties of inclusions on the EHL pressure and film thickness profiles. Both inclusions that are stiffer than and/or softer than the base material are seen to have effects on the pressure distribution within the lubricant film and to give rise to stress concentrations. For inclusions that are stiffer than the base material (hard inclusions), the pressure distribution within the lubricant film behaves as though there is a bump on the surface, whereas for inclusions that are less stiff than the base material (soft inclusions), the pressure distribution behaves in a manner similar to that of a dented surface. Inclusions close to the surface cause significant changes in the contact stresses that are very significant considering the stress life relationship. For inclusions that are located deep within the surface, there is little change in the EHL pressure and film thickness.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Algorithm for the EHL analysis

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Figure 2

A macro-continuum formed by an assemblage of discrete elements

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Figure 3

The elastic half-space formed by square discrete elements

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Figure 4

Comparison of surface elastic deformations for pure Hertzian contact

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Figure 5

(a) Pressure, (b) film thickness, and (c)–(f) sub surface stress profiles for an inclusion-free EHL contact using square elements

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Figure 6

The elastic half-space formed by Voronoi discrete elements

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Figure 7

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles for an inclusion-free EHL contact using Voronoi elements

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Figure 8

Inclusion geometry

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Figure 9

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a horizontally oriented, soft inclusion located close to the surface (y=0.07b)

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Figure 10

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a vertically oriented, soft inclusion located close to the surface (y=0.07b)

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Figure 11

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a horizontally oriented, hard inclusion located close to the surface (y=0.07b)

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Figure 12

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a vertically oriented, hard inclusion located close to the surface (y=0.07b)

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Figure 13

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a horizontally oriented, soft inclusion located deep under the surface (y=0.35b)

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Figure 14

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a vertically oriented, soft inclusion located deep under the surface (y=0.35b)

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Figure 15

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a horizontally oriented, hard inclusion located deep within the surface (y=0.35b)

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Figure 16

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a vertically oriented, hard inclusion located deep under the surface (y=0.35b)

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Figure 17

Nonrectangular inclusion using Voronoi mesh

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Figure 18

(a) Pressure, (b) film thickness, and (c)–(f) subsurface stress profiles in presence of a nonrectangular, horizontally oriented, soft inclusion located close to the surface (y=0.07b)

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Figure 19

Comparison of subsurface von Mises stress profiles in presence of a horizontally oriented, soft inclusion located close to the surface (y=0.07b): (a) Hertzian loading and (b) EHL loading

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Figure 20

Comparison of subsurface von Mises stress profiles in presence of a vertically oriented, soft inclusion located close to the surface (y=0.07b): (a) Hertzian loading and (b) EHL loading

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Figure 21

Comparison of subsurface von Mises stress profiles in presence of a horizontally oriented, hard inclusion located close to the surface (y=0.07b): (a) Hertzian loading and (b) EHL loading

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Figure 22

Comparison of subsurface von Mises stress profiles in presence of a vertically oriented, hard inclusion located close to the surface (y=0.07b): (a) Hertzian loading and (b) EHL loading

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Figure 23

Comparison of subsurface von Mises stress profiles in presence of a horizontally oriented, soft inclusion located deep under the surface (y=0.35b): (a) Hertzian loading and (b) EHL loading

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Figure 24

Comparison of subsurface von Mises stress profiles in presence of a vertically oriented, soft inclusion located deep under the surface (y=0.35b): (a) Hertzian loading and (b) EHL loading

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Figure 25

Comparison of sub-surface von Mises stress profiles in presence of a horizontally oriented, hard inclusion located deep under the surface (y=0.35b): (a) Hertzian loading and (b) EHL loading

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Figure 26

Comparison of sub-surface von Mises stress profiles in presence of a vertically oriented, hard inclusion located deep under the surface (y=0.35b): (a) Hertzian loading and (b) EHL loading

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