Hydrodynamic Performance of Gas Microbearings

[+] Author and Article Information
Daejong Kim, Sanghoon Lee, Michael D. Bryant, Frederick F. Ling

Department of Mechanical Engineering, University of Texas at Austin, Austin, TX 78712

J. Tribol 126(4), 711-718 (Nov 09, 2004) (8 pages) doi:10.1115/1.1792676 History: Received September 17, 2003; Revised April 24, 2004; Online November 09, 2004
Copyright © 2004 by ASME
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Coordinate systems for analysis, where axial coordinate z is out of plane. Here, θR locates the first step with respect to a reference line (dashed), located along the journal eccentricity e_.
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Control volume (after Patankar 12)
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Static performance of gas journal microbearing (θR=5 deg for stepped bearing)
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Load parameters and attitude angles of stepped gas journal microbearing in high eccentricities (ε=0.8)
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Load capacity as a function of step height for thrust bearings
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Nondimensional rotational friction of gas microbearing (θR=5 deg for stepped journal bearings, step height 3 μm for thrust bearings)
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Simulated journal orbits: (a) Orbit A: Converging orbit from origin (stepped gas journal bearing, Λ=0.6, ε0=0.6, ω* =0.4, C=1 μm); Orbit B: Stabilizing motion of journal to (εXY)=(0.694,0.547) by small disturbance at (εX0Y0)=(0.8,0), with Λ=0.6, ω* =0.9. (b) Orbit C: Converging orbit Λ=2, ω* =1.5, ε0=0.8; Orbit D: Diverging orbit Λ=3, ω* =2.7, ε0=0.8.
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Stability chart of gas journal microbearing given as nondimensional threshold speed, ω*
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Motion of journal to (εXY)=(0.694,0.547) from origin for static loading corresponding to (εX0Y0)=(0.8,0) or (0.694,0.547), with Λ=0.6, ω* =0.9. The angle between external the load and the eccentricity vector becomes the attitude angle.
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Stability chart of gas journal microbearing given as the nondimensional threshold mass m*
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Static performance for stepped gas journal bearings with axial grooves (θR=0 deg)
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Load parameter and attitude angle for various step configurations without axial grooves (θR=0 deg, ε=0.6, and Λ=1)
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Gas microbearing: (a) steps are exaggerated and overall diameter is 2 mm, (b) SEM images of overall bearing, (c) SEM images of 2 μm steps on journal bearings before processing thrust bearings




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