An Asperity Contact Model for the Slider Air Bearing

1999 ◽  
Vol 122 (2) ◽  
pp. 436-443 ◽  
Author(s):  
Weidong Huang ◽  
David B. Bogy ◽  
Masayuki Honchi
Keyword(s):  
Direct Simulation Monte Carlo ◽  
Flying Height ◽  
Asperity Contact ◽  
Air Bearing ◽  
Single Asperity ◽  
Bearing Force ◽  
Single Asperity Contact ◽  
Molecular Gas Film Lubrication ◽  
Flying Attitude ◽  
Film Lubrication

As sliders fly closer and closer to the disks, asperity contact is inevitable due to the roughness on the sliders and the disks. A single asperity contact problem was solved using the molecular gas-film lubrication (MGL) model with the no-fly-zone (NFZ) condition, which was discovered with the direct simulation Monte Carlo method (DSMC). It shows that the MGL model can also provide bounded pressure and resultant force in the presence of contact. Moreover, the MGL results agree well with the DSMC results. A database for a single asperity contact force and moment was then created using the MGL model with the NFZ condition. This force and moment was superimposed to the air bearing force calculated by the MGL model calculated by the MGL model when the nominal plane of the slider and the disk are not in contact. The total additional air bearing force due to asperity contact was obtained. Its effect on the slider’s flying attitude was investigated and found to change the flying height and pitch angle up to 20 percent and 10 percent, respectively. [S0742-4787(00)02402-4]

The Effect of the Accommodation Coefficient on Slider Air Bearing Simulation

1999 ◽  
Vol 122 (2) ◽  
pp. 427-435 ◽  
Author(s):  
Weidong Huang ◽  
David B. Bogy
Keyword(s):  
Flow Rate ◽  
Hard Disk Drives ◽  
Direct Simulation Monte Carlo ◽  
Accommodation Coefficient ◽  
Flying Height ◽  
Positive Pressure ◽  
Air Bearing ◽  
Unit Value ◽  
Slider Air Bearing ◽  
Molecular Gas Film Lubrication

In solving the slider air bearing problem, both the Molecular Gas-film Lubrication (MGL) model and the Direct Simulation Monte Carlo (DSMC) model require the accommodation coefficient as input. The accommodation coefficient represents the fraction of the air molecules that interact with solid boundaries in a diffusive manner. In general, the value 1 is used for the accommodation coefficient, which represents a fully diffusive reflection. However, in magnetic hard disk drives, the disk and slider surfaces are becoming ever smoother with different kinds of lubrication on the disk, while the temperature is becoming higher due to the faster spindle speed. Under these conditions the unit value of the accommodation coefficient may no longer be suitable. In order to understand the effect of the accommodation coefficient on the slider’s flying parameters, we used Kang’s new database for the Poiseuille flow rate Qp and Couette flow rate Qc to solve the modified Reynolds equation for two groups of sliders, e.g., negative and positive pressure sliders (“negative” refers to sliders with subambient pressure zones). The results show that, in general, the smaller the accommodation coefficient, the lower the flying height and pitch angle. Positive pressure sliders are more sensitive to the accommodation coefficient than are negative pressure sliders. The typical discrepancy in flying height is around 10%. Also, it is shown that for positive pressure sliders the lower the flying height, the larger the discrepancy percentage. [S0742-4787(00)00402-1]

Air Bearing Models and Solutions for Sub-5 nm Spacings

2001 ◽  
Author(s):  
D. B. Bogy ◽  
Lin Wu
Keyword(s):  
Boundary Condition ◽  
Slip Velocity ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Asperity Contact ◽  
Air Bearing ◽  
Lubrication Equation ◽  
New Equation ◽  
Physical Phenomena ◽  
Flying Attitude

Abstract When the flying height is below 5 nm, some physical phenomena that can be ignored for higher flying sliders need to be included in the modeling equations. Another challenging issue is the unavoidable asperity contact problem. It is known that zero spacing at asperities may cause some of the existing modified Reynolds equations to predict unphysical unbounded contact pressure singularities. In this paper we first review the source of these pressure singularities, showing which models have this problem and which do not. We also review here a new derivation of a compressible lubrication equation by using a different slip velocity boundary condition, in which additional slippage at the gas-solid interface due to pressure gradient is introduced. The new equation is free of any contact singularity [1]. Next we review our recent work on the non-negligible effect of the intermolecular forces on the slider’s flying attitude when the spacing is below 5 nm [2]. The additional force is attractive until the spacing is below about 0.1 nm for example and then it is repulsive. Finally we show the effect of these new force contributions on the flying attitude of a low flying slider.

Performance of Sliders Flying Over Discrete-Track Media

2007 ◽  
Vol 129 (4) ◽  
pp. 712-719 ◽  
Author(s):  
Jianhua Li ◽  
Junguo Xu ◽  
Yuki Shimizu
Keyword(s):  
Estimation Method ◽  
Simulation Method ◽  
Measured Data ◽  
Flying Height ◽  
Height Loss ◽  
Air Bearing ◽  
Slider Air Bearing ◽  
Discrete Track ◽  
Flying Attitude ◽  
Manufacturing Variation

A simulation method in which grooves are virtually distributed on the slider air bearing instead of on the grooved medium surface has been developed and used to investigate the performance of sliders flying over the surface of a discrete-track medium. The simulated flying height loss due to a discrete-track medium coincides well with the measured data, whereas the average-estimation method overestimates flying height loss. Among the characteristics of a slider flying over the surface of a discrete-track medium that were studied are the flying attitude, the effect of groove parameters on flying profile, and the flying height losses due to manufacturing variation and altitude. The results indicate that when a slider is flying over the surface of a discrete-track medium, it will have a higher 3σ of flying height, be more sensitive to altitude, and will have a greater flying height loss.

Contact Mechanics of Rough Surfaces in Tribology: Single Asperity Contact

1996 ◽  
Vol 49 (5) ◽  
pp. 275-298 ◽  
Author(s):  
Bharat Bhushan
Keyword(s):  
Friction And Wear ◽  
Rough Surfaces ◽  
Asperity Contact ◽  
Elastic Solids ◽  
Elastic Plastic ◽  
Single Asperity ◽  
Real Area Of Contact ◽  
Single Asperity Contact ◽  
Indentation Problem ◽  
Real Area

Contact modeling of two rough surfaces under normal approach and with relative motion is carried out to predict the real area of contact which affects friction and wear of an interface. The contact of two macroscopically flat bodies with microroughness is reduced to the contact at multiple asperities of arbitrary shapes. Most of deformation at the asperity contact can be either elastic or elastic-plastic. In this paper, a comprehensive review of modeling of a single asperity contact or an indentation problem is presented. Contact analyses for a spherical asperity/indenter on homogeneous and layered, elastic and elastic-plastic solids with and without tangential loading are presented. The analyses reviewed in this paper fall into two groups: (a) analytical solutions, primarily for elastic solids and (b) finite element solutions, primarily for elastic-plastic problems and layered solids. Implications of these analyses in friction and wear are discussed.

Transitions of Shear Resistance in a Single-Asperity Contact

1998 ◽  
Vol 539 ◽  
Author(s):  
J. A. Hurtado ◽  
K.-S. Kim
Keyword(s):  
Contact Zone ◽  
Shear Force ◽  
Friction Stress ◽  
Adhesive Contact ◽  
Nanometer Scale ◽  
Asperity Contact ◽  
Normal Loading ◽  
Single Asperity ◽  
Single Asperity Contact ◽  
Contact Size

AbstractThe shear force required to emit circular dislocation loops from the edge of a circular adhesive-contact zone is calculated analytically as a function of contact-zone radii. The emission condition is based on the balance of the configurational force and the Peierls force on a dislocation loop initiated at the edge of the adhesive contact zone. The analysis suggests that there is a transition, for a nanometer-scale single-asperity contact, from concurrent (mobile- dislocation-free) slip to single-dislocation-assisted (SDA) slip. The nanometer-scale friction stress (shear force required for slip/contact area), which experimentally is observed independent of normal loading and contact-zone size, is believed to be the stress required for concurrent slip. The analysis also predicts a second transition from SDA slip to multiple-dislocation-cooperated (MDC) slip at the scale of tens of micrometers in contact size. The friction stress at this large length scale has also been observed experimentally to be independent of normal loading and contact size; however, the friction stress at the nanometer scale is about 30 times that at the scale of tens of micrometers. The analysis is consistent with these experimental observations.

Flying Height Deviation Measurements at Ultra Low Fly Heights

2003 ◽  
Author(s):  
Dongman Kim
Keyword(s):  
Attitude Change ◽  
Flying Height ◽  
Air Bearing ◽  
Size Measurement ◽  
Feature Size ◽  
Head Gimbal Assembly ◽  
Air Bearing Slider ◽  
Calibration Techniques ◽  
Flying Attitude

The flying height tester contribution to flying height tolerance is investigated with different calibration techniques in this study. The flying attitude change in head gimbal assembly (HGA) by supplying writing current is discussed along with newly proposed methodology for feature size measurement on the air bearing slider (ABS) using a flying height tester.

scholarly journals Slider Posture Effects on Air Bearing in a Heat-Assisted Magnetic Recording System

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Kyaw Sett Myo ◽  
Weidong Zhou ◽  
Xiaoyang Huang ◽  
Shengkai Yu ◽  
Wei Hua
Keyword(s):  
Magnetic Recording ◽  
Pitch Angle ◽  
Direct Simulation Monte Carlo ◽  
Spot Size ◽  
Air Bearing ◽  
Slider Bearing ◽  
Noticeable Effect ◽  
Heat Assisted Magnetic Recording ◽  
Temperature Changes ◽  
Bearing Force

This paper reports the effects of slider posture on the slider bearing in a heat-assisted magnetic recording (HAMR) system with the direct simulation Monte Carlo (DSMC) method. In this HAMR system, the heat issues on the slider bearings are assumed to be caused by a heated spot on the disk and/or slider body itself at various pitch angles. The simulation results show that with a heated spot on the disk, the air bearing pressure and air bearing force that acted on the slider surface will increase when the pitch angle becomes larger. It is also found that the bearing force increases with the heated spot size and the effects of a heated spot become more obvious at a larger pitch angle. On the other hand, the slider body temperature is observed to have a noticeable effect on air bearing pressure and force. The smaller pitch angle enlarges the tendency of bearing force variations with the slider temperature and makes the slider more sensitive to its temperature changes.

Pre-sliding Behaviour of Single Asperity Contact

2013 ◽  
Vol 49 (3) ◽  
pp. 553-562 ◽  
Author(s):  
M. A. Yaqoob ◽  
A. Winogrodzka ◽  
H. R. Fischer ◽  
E. R. M. Gelinck ◽  
M. B. de Rooij ◽  
...  
Keyword(s):  
Asperity Contact ◽  
Single Asperity ◽  
Single Asperity Contact
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