414 CIP dynamics analysis of molecular gas-film lubrication

This paper proposes an analytical design sensitivity analysis (DSA) to topological parameters of MGL (molecular gas film lubrication) sliders by introducing an adjoint variable method. For the analysis of slider air bearings, we used the spatial discretization of the generalized lubrication equation based on a control volume formulation. The residual functions for inverse analysis of the slider are considered as the equality constraint functions. The slider rail heights of all grid cells are chosen as design variables since they are the topological parameters determining air bearing surface (ABS). Then, a complicated adjoint variable equation is formulated to directly handle the highly nonlinear asymmetric coefficient matrix and vector in the discrete system equations of slider air bearings. An alternating direction implicit (ADI) scheme is utilized to efficiently solve large-scale problem in special band storage. The simulation results of DSA are directly compared with those of finite-difference approximation (FDA) to show the effectiveness and accuracy of the proposed approach. The overall sensitivity distribution over the ABS is reported, and clearly shows to which section of the ABS the special attention should be given during the manufacturing process. It is demonstrated that the proposed method can reduce more than 99 percent of the CPU time in comparison with FDA, even though both methods give the same results.

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Simplified molecular gas film lubrication equation and accommodation coefficient effects

Microsystem Technologies ◽

10.1007/s00542-011-1299-6 ◽

2011 ◽

Vol 17 (8) ◽

pp. 1271-1282 ◽

Cited By ~ 6

Author(s):

Bao-Jun Shi ◽

Jia-Dong Ji ◽

Ting-Yi Yang

Keyword(s):

Accommodation Coefficient ◽

Molecular Gas ◽

Lubrication Equation ◽

Molecular Gas Film Lubrication ◽

Film Lubrication

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Molecular Gas Film Lubrication

Encyclopedia of Tribology ◽

10.1007/978-0-387-92897-5_236 ◽

2013 ◽

pp. 2309-2313 ◽

Cited By ~ 1

Author(s):

Sheng Shen ◽

Gang Chen

Keyword(s):

Molecular Gas ◽

Molecular Gas Film Lubrication ◽

Film Lubrication

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A Database for Couette Flow Rate Considering the Effects of Non-Symmetric Molecular Interactions

Journal of Tribology ◽

10.1115/1.1479700 ◽

2002 ◽

Vol 124 (4) ◽

pp. 869-873 ◽

Cited By ~ 15

Author(s):

Wang-Long Li

Keyword(s):

Couette Flow ◽

Molecular Interactions ◽

Flow Rate ◽

Molecular Gas ◽

Mems Devices ◽

Magnetic Head ◽

Linearized Boltzmann Equation ◽

Accommodation Coefficients ◽

Molecular Gas Film Lubrication ◽

Film Lubrication

A complete database for Couette flow rate (QCD,α1,α2,0.1⩽α1,α2⩽1.0,0.01⩽D⩽100, where D=inverse Knudsen number) for ultra-thin gas film lubrication problems is advanced. When the accommodation coefficients (AC) of the two lubricating surfaces are different α1≠α2, the Couette flow rate in the modified molecular gas film lubrication (MMGL) equation should be corrected. The linearized Boltzmann equation (under small Mach number conditions) is solved numerically for the case of non-symmetric molecular interactions α1≠α2. The Couette flow rate is then calculated, and the database is constructed. The present database can be easily implemented in the MMGL equation. In addition, the present database extends the previously published results for 0.1⩽α1,α2⩽0.7. The database for low ACs is valuable in the analysis and applications of MEMS devices (bushings of electrostatic micro motors, micro bearings, magnetic head/disk interfaces, etc.), and their future development.

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Thermo-Molecular Gas-Film Lubrication (t-MGL) Considering Temperature Distributions and Accommodation Coefficients: Analyses by Quasi-Free-Molecular t-MGL Equation

ASME-JSME 2018 Joint International Conference on Information Storage and Processing Systems and Micromechatronics for Information and Precision Equipment ◽

10.1115/isps-mipe2018-8569 ◽

2018 ◽

Author(s):

Shigehisa Fukui ◽

Fumiya Shinohara ◽

Ryota Asada ◽

Hiroshige Matsuoka

Keyword(s):

Specular Reflection ◽

Flow Region ◽

Molecular Flow ◽

Molecular Gas ◽

Gas Temperature ◽

Accommodation Coefficients ◽

Ambient Gas ◽

Molecular Gas Film Lubrication ◽

Local Temperature Distribution ◽

Film Lubrication

In the present paper, the flying characteristics of a step slider flying in either air or He with a local temperature distribution of the disk are analyzed using the thermo-molecular gas-film lubrication (t-MGL) equation in the quasi-free-molecular flow region (quasi-free-molecular t-MGL equation: t-MGLqfm eq.). The gas temperature in the t-MGLqfm equation, τG, is assumed to be that in the free molecular limit, τGfm, defined by temperatures and accommodation coefficients at the disk, τW0, α0, and those at the slider, τW1, α1, respectively. The decreases in static spacing for the slider flying in He are significant. Moreover, the spacing decreases as the accommodation coefficients of the disk, α0, decreases, that is, as the ratio of specular reflection increases. The spacing fluctuation caused by a running wavy disk varies according to both the ambient gas (air/He) and the boundary accommodation coefficients.

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