The Effect of Two-Dimensional Surface Roughness on the Load-Carrying Capacity of a Thin Compressible Gas Film

1993 ◽  
Vol 115 (2) ◽  
pp. 246-252 ◽  
Author(s):  
J. W. White
Keyword(s):  
Surface Roughness ◽  
Data Storage ◽  
Perturbation Expansion ◽  
Expansion Method ◽  
Order Effect ◽  
Finite Width ◽  
Two Dimensional ◽  
Lubrication Equation ◽  
Unit Depth ◽  
Dimensional Surface

The influence of two-dimensional surface roughness on a very low clearance gas bearing slider is analyzed for conditions typical of current and near term hard disk data storage products. A model lubrication equation including finite width effects, compressibility and molecular slip is first developed and expressed in terms of the product variable, Z = PH. The analytical solution is then obtained by a combined variation of parameters and perturbation expansion method. Results obtained show that the product variable, which is proportional to longitudinal mass flow per unit depth, is not influenced by the details of surface roughness but is instead influenced by the statistics of the roughness distribution. The gas film pressure, however, is found to be a function of both the roughness details and statistics. The bearing load support is increased by the surface roughness, with the roughness first influencing the load through a second order effect.

A Lubrication Equation Incorporating Two-Dimensional Roughness Effects, With Emphasis on the Patterned Data Islands of a Recording Disk

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
James White
Keyword(s):  
Surface Roughness ◽  
Multiple Scale ◽  
Industrial Applications ◽  
Two Dimensional ◽  
Roughness Effects ◽  
Design And Optimization ◽  
Lubrication Equation ◽  
Wide Range ◽  
Level Of Understanding ◽  
Dimensional Surface

Current industrial applications require a consideration of two-dimensional surface roughness effects in design and optimization of fluid bearings. Although the influence of striated surface roughness on fluid lubrication is now at a fairly mature level of understanding, the knowledge and understanding of two-dimensional roughness effects is not nearly at the same level as that achieved over the past several decades for one-dimensional striations. The subject of this paper includes the formulation of a practical “roughness averaged” lubrication equation that is appropriate for two-dimensional surface roughness and applicable over a wide range of Knudsen numbers. After derivation by multiple-scale analysis, the resulting lubrication equation is specialized to treat the patterned data islands located on a storage medium as a two-dimensional roughness pattern, and then used to determine the effect of this roughness on the air-bearing interface between recording head slider and disk. The roughness averaged lubrication equation is solved numerically by a variable-grid finite-difference algorithm, and computed results are included for several bearing geometries.

On the effects of two-dimensional Reynolds roughness in hydrodynamic lubrication

1978 ◽  
Vol 364 (1716) ◽  
pp. 89-106 ◽  
Keyword(s):  
Surface Roughness ◽  
Numerical Computation ◽  
Autocorrelation Function ◽  
Reynolds Equation ◽  
Hydrodynamic Lubrication ◽  
The Other ◽  
Roughness Height ◽  
Two Dimensional ◽  
Roughness Effects ◽  
Dimensional Surface

The hydrodynamic lubrication of rough surfaces is analysed with the Reynolds equation, whose application requires the roughness spacing to be large, and the roughness height to be small, compared with the thick­ness of the fluid film. The general two-dimensional surface roughness is considered, and results applicable to any roughness structure are obtained. It is revealed analytically that two types of term contribute to roughness effects: one depends on the shape of the autocorrelation function and the other does not. The former contribution was neglected by previous workers. The numerical computation of an example shows that these two contributions are comparable in magnitude.

Application of Process Analysis Method to the Solution of 2-DNonlinear Progressive Gravity Waves

1992 ◽  
Vol 36 (01) ◽  
pp. 30-37
Author(s):  
S. J. Liao
Keyword(s):  
Gravity Waves ◽  
Process Analysis ◽  
Perturbation Expansion ◽  
Continuous Mapping ◽  
Nonlinear Problems ◽  
Expansion Method ◽  
Order Of Approximation ◽  
Two Dimensional ◽  
Analysis Method ◽  
Perturbation Expansion Method

Based on continuous mapping, a kind of analytical method for nonlinear problems, namely, the Process Analysis Method, is described and used to solve two-dimensional nonlinear progressive gravity waves. Solutions at the fourth order of approximation are obtained and compared with Stokesian waves. In contrast to the perturbation expansion method, the Process Analysis Method is independent of small or great parameters and therefore can solve nonlinear problems without small or great parameters.

Bearing condition assessment. Part 1: Size and frequency of surface roughness interactions in impulsive vibration measurements

2003 ◽  
Vol 217 (6) ◽  
pp. 435-445 ◽  
Author(s):  
M Ho ◽  
D. J. Birch ◽  
P. J. Brunn
Keyword(s):  
Surface Roughness ◽  
Gaussian Distribution ◽  
Piezoelectric Transducer ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Two Dimensional ◽  
Rolling Bearings ◽  
Innovative Method ◽  
Lubrication Conditions ◽  
Dimensional Surface

Impulsive vibrations generated during the operation of a rolling Hertzian line contact under elastohydrodynamic lubrication (EHL) conditions, typically found in tapered rolling bearings, are analysed using two-dimensional surface roughness profiles containing spherical asperities. The cause of these vibrations is modelled as a series of collisions between the asperities forming the surfaces in contact. Asperity heights are considered to vary according to a Gaussian distribution, and an innovative method, based upon probability, is developed so that the rates and the magnitudes of collisions between asperities of various heights under different lubrication conditions can be studied. The magnitude of individual collisions are predicted to allow them to be compared with those measured using a calibrated master piezoelectric transducer.

Factored-lmplicit Finite Difference Solution of a Non-Newtonian Fluid Lubrication Equation for Three-Dimensional Bearings

1996 ◽  
Vol 118 (4) ◽  
pp. 824-831 ◽  
Author(s):  
J. W. White
Keyword(s):  
Shear Stress ◽  
Finite Difference ◽  
Strain Rate ◽  
Data Storage ◽  
Newtonian Fluid ◽  
Time Interval ◽  
Finite Width ◽  
Disk Interface ◽  
Static And Dynamic Analysis ◽  
Lubrication Equation

A time dependent lubrication equation is developed for a non-Newtonian fluid whose shear stress is expressed in terms of instantaneous strain rate. By expanding the shear stress through a two function Taylor series, the stress/strain-rate relationship is linearized within the time interval (tn ≤ t ≤ tn+1) but accurate to O(Δt2). This produces a linear lubrication equation which is second-order time-accurate. The resulting finite difference form of the lubrication equation is then factored and split into two equations, each of which represents a sequence of one-dimensional systems of tri-diagonal scalar equations. A finite difference code based on this algorithm was written called VISQUSFLO which provides static and dynamic analysis of the head/disk interface of data storage systems. Numerical examples of a shear-thinning fluid are presented for clearances in the range of 25-50 nm for finite width slider bearings.

Rarefied gas flow between two flat plates with two dimensional surface roughness

Vacuum ◽  
1996 ◽  
Vol 47 (6-8) ◽  
pp. 791-794 ◽  
Author(s):  
Wataru Sugiyama ◽  
Ta-i Sawada ◽  
Kenji Nakamori
Keyword(s):  
Surface Roughness ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Two Dimensional ◽  
Rarefied Gas Flow ◽  
Flat Plates ◽  
Dimensional Surface
Sign in / Sign up

Export Citation Format

Share Document