Detection of the Asperity Contact Between Sliding Surfaces by Monitoring the Excitation of Resonant Oscillation Using the Fiber Wobbling Method

2007 ◽  
Author(s):  
Shintaro Itoh ◽  
Kenji Fukuzawa ◽  
Yuya Hamamoto ◽  
Hedong Zhang ◽  
Yasunaga Mitsuya
Keyword(s):  
Viscoelastic Properties ◽  
Lubricant Film ◽  
Solid Surfaces ◽  
Asperity Contact ◽  
Magnetic Head ◽  
Magnetic Disk ◽  
Disk Interface ◽  
Starting Point ◽  
Lubrication Performance ◽  
Lubricant Films

In the head disk interface (HDI) of a magnetic recording system, lubrication caused by a monolayer thick lubricant film is necessary to achieve stable relative motion between a magnetic disk and a magnetic head. Viscoelastic properties of lubricant films should be clarified for improvement of lubrication performance, however, measurement methods have not been established yet. In this study, we present a new method precisely detecting the starting point of asperity contact of sliding solid surfaces in order to measure viscoelastic properties of the molecularly thin lubricant film on the magnetic disk.

Depletion of Moleculary Thin Lubricant Under Flying Head in Hard Disk Drives

2007 ◽  
Author(s):  
Kenji Yanagisawa ◽  
Youichi Kawakubo ◽  
Masato Yoshino
Keyword(s):  
Thin Film ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Lubricant Film ◽  
Simulation Program ◽  
Disk Drives ◽  
Lubricant Thickness ◽  
Magnetic Disk ◽  
Lubricant Depletion ◽  
Lubricant Films

In Hard Disk Drives, lubricants are very important materials to reduce head and disk wear. Therefore, it is necessary to know the lubricant depletion under flying heads. Lubricant depletion due to flying heads has been studied experimentally. We developed simulation program to calculate numerically the change in lubricant thickness under a flying head on a thin-film magnetic disk from 10nm thick lubricant film. In recent HDDs, the lubricants thickness has become molecularly thin and polar lubricants have been used. In this paper, we took account of thickness-dependent lubricants diffusion and viscosity in our simulations to calculate a 1.2 nm thick polar lubricant film used in recent HDDs. The simulated results considering the thickness-dependent diffusion and viscosity showed that depletion was small in molecularly thin lubricant films. We considered it necessary to include thickness-dependent diffusion and viscosity in lubricant depletion simulation.

Experimental and Theoretical Analysis of Magnetic Head-Disk Interface Equilibrium in the “Rupture” Regime of the Starved-Liquid Bearing

1997 ◽  
Vol 119 (3) ◽  
pp. 515-519 ◽  
Author(s):  
J. L. Streator
Keyword(s):  
Friction Force ◽  
Optical Probe ◽  
Lubricant Film ◽  
Head Disk Interface ◽  
Magnetic Head ◽  
Partial Loss ◽  
Disk Interface ◽  
Loss Of Contact ◽  
Friction Measurements ◽  
Apparent Shear Rate

Previous friction measurements in the magnetic head-disk interface (HDI) indicated some anomalous friction force behavior with low sliding speeds (.25 mm/s to 0.25 m/s) and lubricant film thicknesses in the range of 20–80 nm, showing decreasing friction force with increasing apparent shear rate. The physical explanation for such behavior has not yet been established. Possible explanations for such behavior have included dramatic shear thinning, interfacial slip and partial loss of contact with the lubricant film due to slider tipping. In the present study, we investigate the possibility of slider tipping as an explanation for the decreasing friction force with increasing sliding speed. Measurements with an optical probe indicate that slider tipping does not occur for the conditions tested. Numerical analysis of slider equilibrium also supports this conclusion.

Derivation of Rarefaction-Modified Reynolds Equation Considering Porosity of Thin Lubricant Film

1997 ◽  
Vol 119 (4) ◽  
pp. 653-659 ◽  
Author(s):  
Yasunaga Mitsuya ◽  
Zhisheng Deng ◽  
Masahiro Ohka
Keyword(s):  
Reynolds Equation ◽  
Lubricant Film ◽  
The Other ◽  
Magnetic Head ◽  
Permeable Material ◽  
Magnetic Medium ◽  
Magnetic Disk ◽  
Head Slider ◽  
Liquid Lubricant ◽  
Modified Reynolds Equation

A new lubrication model is derived for solving ultra-thin gas lubrication problems encountered in the analysis of a magnetic head slider flying over a magnetic disk coated with giant-molecule lubricant film. In this model, the liquid lubricant film is replaced with a permeable material, and the boundary between the gas and liquid is subject to two kinds of velocity slippage: one due to the rarefaction effect and the other to the porous effect. Using this model, a rarefaction-modified Reynolds equation is derived considering the permeability of the running surface. This equation is then applied to the lubrication of head sliders flying over a magnetic medium. An interesting condition is found to arise wherein total apparent slippage seems to disappear due to the cancellation of the two slippages and the permeability effects are larger for a slider having a steeper pressure gradient.

Effect of Thermal Bonding on Frictional Properties of Monolayer Lubricant Films Coated on Magnetic Disk Surfaces

2008 ◽  
Vol 44 (11) ◽  
pp. 3637-3640 ◽  
Author(s):  
Hedong Zhang ◽  
Y. Mitsuya ◽  
A. Fuwa ◽  
Y. Fujikawa ◽  
K. Fukuzawa
Keyword(s):  
Thermal Bonding ◽  
Magnetic Disk ◽  
Frictional Properties ◽  
Lubricant Films

Study of Direct Measuring of Lubricant Condition in Rolling Element Bearings With Microcomputer Technique

1990 ◽  
Vol 112 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Dongchu Zhao
Keyword(s):  
Film Thickness ◽  
Strain Gage ◽  
Lubricant Film ◽  
Rolling Element Bearings ◽  
Main Program ◽  
Test Apparatus ◽  
Lubricant Film Thickness ◽  
Rolling Element ◽  
Lubricant Films ◽  
Flow Charts

A method for measuring the lubricant condition with strain gage in rolling element bearings and the instrument used are introduced. In order to illustrate the method and the instrument, the theory of measuring lubricant films in rolling element bearings using strain technique, test apparatus, microcomputer hardware as well as software, flow charts for the main program and subprograms, are first described in detail. In addition, the lubricant film thickness is measured for several different lubricants and results are compared with theoretical ones. It is demonstrated that using the method and the instrument introduced in this paper, one can measure the lubricant condition inside bearings very accurately.

scholarly journals Effects of bushing profiles on the elastohydrodynamic lubrication performance of the journal bearing under steady operating conditions

2019 ◽  
Vol 20 (2) ◽  
pp. 207 ◽  
Author(s):  
Chongpei Liu ◽  
Bin Zhao ◽  
Wanyou Li ◽  
Xiqun Lu
Keyword(s):  
Journal Bearing ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Parabolic Profile ◽  
Leakage Flow Rate ◽  
Lubrication Performance ◽  
Load Carrying ◽  
Edge Wear ◽  
Flow Rate Change

The bushing profiles have important effects on the performance of journal bearing. In this article, the effects of plain profile, double conical profile, and double parabolic profile on the elastohydrodynamic lubrication of the journal bearing under steady operating conditions are investigated. The journal misalignment and asperity contact between journal and bushing surface are considered, while the modification of the bushing profiles due to running-in is neglected. Finite element method is used for the elastic deformation of bushing surface, while the numerical solution is established by using finite difference method and overrelaxation iterative method. The numerical results reveal that the double parabolic profile with appropriate size can significantly increase the minimum film thickness and reduce the asperity contact pressure and friction, while the maximum film pressure, load-carrying capacity, and leakage flow rate change slightly under steady operating conditions. This study may help to reduce the edge wear and prolong the service life of the journal bearing.

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