scholarly journals Homogenization and two-scale convergence of the compressible Reynolds lubrication equation modelling the flying characteristics of a rough magnetic head over a rough rigid-disk surface

1995 ◽  
Vol 29 (2) ◽  
pp. 199-233 ◽  
Author(s):  
M. Jai
Keyword(s):  
Disk Surface ◽  
Magnetic Head ◽  
Rigid Disk ◽  
Lubrication Equation ◽  
Equation Modelling

Improvement of the Static and Dynamic Characteristics of Magnetic Head Sliders by Optimum Design

1999 ◽  
Vol 122 (1) ◽  
pp. 280-287 ◽  
Author(s):  
Hiromu Hashimoto ◽  
Yasuhisa Hattori
Keyword(s):  
Objective Function ◽  
Optimum Design ◽  
Amplitude Ratio ◽  
Optimization Technique ◽  
Hard Disk Drives ◽  
Maximum Amplitude ◽  
Disk Surface ◽  
Operating Conditions ◽  
Magnetic Head ◽  
Design Variables

The aim of this paper is to develop a general methodology for the optimum design of magnetic head sliders in improving the spacing characteristics between a slider and disk surface under static and dynamic operating conditions of hard disk drives and to present an application of the methodology to the IBM 3380-type slider design. To generate the optimal design variables, the objective function is defined as the weighted sum of the minimum spacing, the maximum difference in the spacing due to variation of the radial location of the head, and the maximum amplitude ratio of the slider motion. Slider rail width, taper length, taper angle, suspension position, and preload are selected as the design variables. Before the optimization of the head, the effects of these five design variables on the objective function are examined by a parametric study, and then the optimum design variables are determined by applying the hybrid optimization technique, combining the direct search method and successive quadratic programming. From the obtained results, the effectiveness of optimum design on the spacing characteristics of magnetic heads is clarified. [S0742-4787(00)03701-2]

Computer Rigid Disk Surface Assessment With Laser Interferometry Using DDS

1996 ◽  
Vol 118 (3) ◽  
pp. 448-455 ◽  
Author(s):  
S. M. Pandit ◽  
N. Jordache ◽  
G. A. Joshi
Keyword(s):  
Laser Interferometry ◽  
Complex Surface ◽  
Disk Surface ◽  
Manufacturing Processes ◽  
Height Profile ◽  
Surface Textures ◽  
Rigid Disk ◽  
Reliable Computation ◽  
Resultant Effect ◽  
Surface Assessment

Laser interferometry in conjunction with the data dependent systems (DDS) methodology is first used in this paper to eliminate errors caused by instrumentation and software, and to recover the surface topography of a computer rigid disk used for illustration. The DDS methodology is then applied once more to decompose the surface height profile into a series of exponential and sinusoidal modes. The significant modes are related to the waviness and surface roughness resulting from different manufacturing processes. Surface reconstruction using only the important modes is presented. This provides a visual as well as mathematical description of the resultant effect of each process. The methodology can characterize very complex surface textures, reducing the reliance on complicated and expensive instruments needed for inspection, and replacing them with relatively inexpensive but reliable computation.

scholarly journals A Dynamic Model of the Magnetic Head Slider With Contact and Off-Track Motion due to a Thermally Actuated Protrusion or a Moving Bump Involving Intermolecular Forces

2016 ◽  
Author(s):  
Saurabh Pathak ◽  
Shao Wang
Keyword(s):  
Dynamic Model ◽  
Rotating Disk ◽  
Disk Surface ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Magnetic Head ◽  
Computationally Efficient ◽  
Normal Contact ◽  
Head Slider ◽  
Thermally Actuated

A computationally efficient five-degree-of-freedom dynamic model was developed to simulate the motion of a magnetic head slider under the conditions of moving-bump collision and of contact due to an expanding protrusion on the slider for thermal flying-height control, with consideration of intermolecular forces. Compared to results obtained without intermolecular forces for a bump on the rotating disk, the intermolecular forces cause a significantly greater normal contact force, a larger roll angle and a larger off-track displacement under nonzero skew. When an expanding protrusion on the slider reaches a position close to the disk surface, the intermolecular forces pull the slider into contact at an earlier time and keep the protrusion in contact for a longer duration, which, with friction under nonzero skew, results in a substantially greater off-track displacement.

Ultrathin Liquid Lubrication of Magnetic Head–Rigid Disk Interface for Near-Contact Recording: Part II—Shear Thinning and Thermal Thinning

1996 ◽  
Vol 118 (2) ◽  
pp. 396-401 ◽  
Author(s):  
Hsing-Sen S. Hsiao ◽  
Bharat Bhushan ◽  
Bernard J. Hamrock
Keyword(s):  
Characteristic Curve ◽  
Shear Thinning ◽  
Magnetic Head ◽  
Hydrodynamic Analysis ◽  
Disk Interface ◽  
Rigid Disk ◽  
Curve Fit ◽  
Stress Curve ◽  
Contact Recording ◽  
Raphson Method

The Carreau shear thinning equation and the modified Roelands thermal thinning equation are combined by using the generalized master curve approach to construct a new thermal non-Newtonian rheology model. The Newton-Raphson method is then used to curve-fit existing experimental data for two perfluoropolyethers to this new model. The thermophysical properties thus found are then used to calculate thermal and shear thinning correction factors for the ultrathin liquid lubrication of magnetic head-rigid disk interfaces. The results of rheology modeling show excellent fits of the widely ranging raw data with the new thermal non-Newtonian model. The results of hydrodynamic analysis indicate that the friction force-isothermal Newtonian shear stress curve for these interfaces is simply a lubricant characteristic curve of thermal-shear thinning.

The Simulation of Laser Cleaning of Magnetic Head with Different Temporal Pulses

2015 ◽  
Vol 1101 ◽  
pp. 446-452 ◽  
Author(s):  
Narongpun Rungcharoen ◽  
Mongkol Wannapapra ◽  
Wanchai Pijitrojana
Keyword(s):  
Hard Disk Drives ◽  
Disk Surface ◽  
Laser Cleaning ◽  
User Requirements ◽  
Particle Removal ◽  
Disk Drives ◽  
Magnetic Head ◽  
Small Particles ◽  
Fly Height ◽  
Non Destructive

Nowadays, hard disk drives (HDD) technology are being developed continuously in order to increase the capacity, and reduce the size of HDD to meet user requirements. To increase the capacity which is equivalent to increasing read/write ability, the flying clearance must be reduced. Current new HDD models show that the fly height is lower than 0.3 μm. If the height of a particle or contamination is higher than 0.3 μm, the magnetic head will scratch the magnetic disk surface. However the process of cleaning in the HDD industry cannot remove particles with size smaller than 0.3 μm [1]. Therefore laser cleaning is selected first because this method can remove small particles [2]. and it does not damage the magnetic head. This research compares the range of temperature needed for cleaning the magnetic head between two types of heat source’s profile. The technique used is the heat transfer by finite element: FEM[3]. This technique provides an important factor of the laser cleaning method that increases the efficiency of particle removal. It is also a non-destructive method for cleaning the surface of the magnetic head slider.

Change in Film Thickness Profile of Perfluoropolyethers During Dewetting

2007 ◽  
Author(s):  
S. Ohno ◽  
T. Kato ◽  
M. Kawaguchi
Keyword(s):  
Film Thickness ◽  
Hard Disk Drives ◽  
Stable State ◽  
Magnetic Layer ◽  
Disk Surface ◽  
Intermolecular Forces ◽  
Dip Coating ◽  
Magnetic Head ◽  
Thickness Profile ◽  
Metastable Condition

The physical spacing between a magnetic head and a disk surface has been decreasing in order to achieve the higher recording density for hard disk drives (HDD), and a new head/disk system, such as the contact type, has been proposed in recent years. However, a molecularly-thin PFPE film dewets due to intermolecular forces particularly when the polar interaction is predominant which results in the formation of microdroplets. It was reported that the microdroplets on the disk surface attacked the magnetic head, caused a fluctuation in the physical spacing and made the flying head unstable. Therefore, the precise investigation of the dewetting at head disk interfaces (HDI) is fundamentally needed. The substrates evaluated in this study were 2.5inch glass disks used for HDD. These glass disks are comprised of a magnetic layer and diamond-like carbon (DLC) overcoat, of which the DLC thickness is about 3nm, and have a textured pattern on the surface. PFPE Zdol diluted with HFE-7100DL was coated on the disk surface by a dip-coating method. The change in the film thickness profile was investigated using an ellipsometer for the film under an unstable or metastable condition. It was found from the observation of the unstable film that the development of microdroplets indicates the movement of PFPE molecules through the under layer. For the metastable condition, the surface texture triggered the dewetting and affected the formation of microdroplets. In the “thicknesses spectrum”, a sharp peak was seen at about 7.8nm immediately after the dip-coating, but before the occurrence of dewetting. The peak at 7.8nm easily disappeared and another peak at about 1.6nm appeared instead. This means that the 7.8nm thickness film was unstable and moved to a more stable state. It is noted that the microdroplets were formed by this instability, and the 1.6 nm thickness corresponded to that of the dewetted area.

Numerical Solution of the Boltzmann Based Lubrication Equation for the Air-Bearing Interface Between a Skewed Slider and a Disk With Discrete Data Tracks

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
James White
Keyword(s):  
Numerical Solution ◽  
Data Storage ◽  
Knudsen Number ◽  
Numerical Solutions ◽  
Disk Surface ◽  
Air Bearing ◽  
Skew Angle ◽  
Lubrication Equation ◽  
Highly Nonlinear ◽  
Discrete Track

Discrete track recording (DTR) is a method for increasing the recording density of a data storage disk by use of a pattern arrangement of discrete tracks. The DTR track structure consists of a pattern of very narrow concentric raised areas and recessed areas underneath a magnetic recording layer. In order to design the air-bearing slider platform that houses the magnetic transducer for DTR application at very low fly heights, the influence of the disk surface topography as a surface roughness effect must be taken into account. This paper is focused on the numerical solution of the roughness averaged lubrication equation reported recently in the work of White (2010, “A Gas Lubrication Equation for High Knudsen Number Flows and Striated Rough Surfaces,” ASME J. Tribol., 132, p. 021701) and is specialized for the influence of discrete disk data tracks on the recording head slider-disk air-bearing interface subject to a nonzero skew angle formed between the slider longitudinal axis and the direction of disk motion. The generalized lubrication equation for a smooth surface bearing and appropriate for high Knudsen number analysis is quite nonlinear. And including the averaging process required for treatment of a nonsmooth disk surface, as well as the rotational transformation required to allow for a nonzero skew angle, increases further the nonlinearity and general complexity of the lubrication equation. Emphasis is placed on development of a numerical algorithm that is fast, accurate, and robust for air-bearing analysis of complex slider surfaces. The numerical solution procedure developed utilizes a time integration of the lubrication equation for both steady-state and dynamic analyses. The factored-implicit scheme, a form of the more general alternating-direction-implicit numerical approach, was chosen to deal with the two-dimensional and highly nonlinear aspects of the problem. Factoring produces tightly banded coefficient matrices and results in an algorithm that is second-order accurate in time while requiring only the solution of tridiagonal systems of linear equations in advancing the computation from one time level to the next. Numerical solutions are presented that demonstrate the performance of the computational scheme and illustrate the influence of some discrete track parameters on skewed air-bearing performance as compared with a flat surface data storage disk.

Dynamic Flying Characteristics of Magnetic Head Slider With Dust

1994 ◽  
Vol 116 (1) ◽  
pp. 95-100 ◽  
Author(s):  
Mikio Tokuyama ◽  
Shinichi Hirose
Keyword(s):  
Disk Surface ◽  
Numerical Results ◽  
Flying Height ◽  
Magnetic Head ◽  
Head Slider ◽  
Air Lubrication

The dust adhering to the taper of a slider changes the shape of its flying rail and decreases the efficiency of air lubrication that determines its flying height. The dynamic flying height characteristics of the slider with dust at its taper are numerically and experimentally examined. The numerical results show that a triangular accumulation of dust at the tapered portion of the slider degrades the motion-following performance of the slider as it covers the runout of the magnitude disk surface. A dust adhesion experiment revealed that dust at the tapered portion decreased the flying height and increased flying height fluctuations. The disk runout is considered a major reason for the fluctuation increase.

Spacing Modulation of Magnetic Head Due to Topographical Feature of Disk Surface

1998 ◽  
Vol 120 (3) ◽  
pp. 542-548 ◽  
Author(s):  
Shoji Suzuki
Keyword(s):  
High Resolution ◽  
Smooth Surface ◽  
Disk Surface ◽  
Magnetic Head ◽  
Signal Modulation ◽  
Height Range ◽  
Smooth Disk ◽  
Topographical Feature ◽  
Fly Height ◽  
Ramp Load

To achieve high recording density, the combination of low flying head and smooth disk surface is very desirable. Although high stiction associated with the smooth surface can be avoided by zone texturing or ramp load, stable flying condition must be assured by a smooth disk surface. Disk topography is an important factor in the flying stability of the head. In this work, read back signal modulation analysis was incorporated to characterize the disk topography. By increasing the writing frequency up to 25 MHz, high resolution was demonstrated in the fly height range between 15 nm to 50 nm. This resolution is sufficient to evaluate today’s low flying heads. A subambient pressure design which is typical for an MR head and a proximity head design for an inductive head were evaluated over very smooth aluminum disks. The effect of various disk clamping forces was also investigated. Relationship between disk waviness and flying stability of heads was studied.

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