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TECHNICAL PAPERS

Soft Elastohydrodynamic Analysis of Radial Lip Seals With Deterministic Microasperities on the Shaft

[+] Author and Article Information

Bearings and Seals Laboratory, University of Kentucky, 151 RGAN Building, Lexington, Kentucky 40506-0503pchadi0@engr.uky.edu

Lyndon Scott Stephens

Bearings and Seals Laboratory, University of Kentucky, 151 RGAN Building, Lexington, Kentucky 40506-0503

J. Tribol 129(4), 851-859 (Apr 02, 2007) (9 pages) doi:10.1115/1.2768087 History: Received March 14, 2006; Revised April 02, 2007

Abstract

A numerical analysis is conducted to investigate the elastohydrodynamic effect of deterministic microasperities on the shaft of a lip seal. Various geometries of microasperities (triangular, square, hexagonal, and circular) are put into a $100×100μm2$ unit cell and are investigated using Reynolds equation. For each shape, the area fraction of the microasperity is varied between 0.2 and 0.8, and the asperity height is varied between $0.3μm$ and $5μm$. The calculation for load capacity and friction coefficient indicates that there are values for asperity height, where the load capacity and friction coefficient are optimized. These optimum heights were reached at $1–3μm$. Although the lip seal surface is considered to be smooth, reverse pumping can still be obtained using an oriented triangular design. The Couette flow rate for this asperity showed lubricant is reverted back toward the seal side 2.6 times more than using a conventional lip seal. The addition of microasperities to the shaft surface shows significant improvement in lubrication characteristics for the lip seal in the form of a simultaneous reduction in friction coefficient and increase in the reverse pumping rate.

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Figures

Figure 1

(a) Typical lip seal arrangement (24) and (b) cross section of lip seal contact region

Figure 2

Hexagonal asperities, 165μm edge to edge, 550μm diameter, 15μm tall, developed at Bearings and Seals Laboratory, University of Kentucky

Figure 3

Lip seal schematic

Figure 4

Asperity geometries

Figure 5

Finite element representation for lip seal (taken using ANSYS ®)

Figure 6

Typical lip seal deformation over asperity

Figure 7

Typical hydrodynamic pressure distribution

Figure 8

Figure 9

Friction coefficient

Figure 10

Side flow Qy

Figure 11

Flow models: (a) Microundulation model and (b) Asymmetric asperity model

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