Improved Analysis of Unstable Bouncing Vibration and Stabilizing Design of Flying Head Slider in Near-Contact Region

2006 ◽  
Vol 129 (1) ◽  
pp. 65-74 ◽  
Author(s):  
Kyosuke Ono ◽  
Masami Yamane
Keyword(s):  
Parametric Study ◽  
Contact Region ◽  
Disk Surface ◽  
Design Guidelines ◽  
Flying Height ◽  
Asperity Contact ◽  
Adhesion Forces ◽  
Characteristic Model ◽  
Head Slider ◽  
Contact Characteristic

This paper describes an improved analytical study of the bouncing vibration of a flying head slider in the near-contact region and gives quantitative designs guideline for realizing a stable flying head slider, based on the results of a parametric study. First, we numerically calculated the general characteristics of the contact and adhesion forces between a smooth contact pad and disk surface by considering asperity contact, the lubricant meniscus, and elastic bulk deformation. As a result, it was shown that the contact characteristics can be represented by a simple model with five independent parameters when the asperity density is large and the asperity height is small as in cases of current slider and disk surfaces. Then, we numerically computed the slider dynamics in a two degree of freedom slider model with nonlinear air-bearing springs by using the simplified contact characteristic model. As a result, we have obtained a self-excited bouncing vibration whose frequency, amplitude and touchdown/takeoff hysteresis characteristics agree much better with the experimental results compared with our previous analysis. From a parametric study for takeoff height, we could obtain design guidelines for realizing a stable head slider in a low flying height of 5nm or less.

Experimental and Theoretical Investigation of Bouncing Vibrations of a Flying Head Slider in the Near-Contact Region

2006 ◽  
Vol 129 (2) ◽  
pp. 246-255 ◽  
Author(s):  
Kyosuke Ono ◽  
Masami Yamane
Keyword(s):  
Vibration Amplitude ◽  
Contact Region ◽  
Ambient Pressure ◽  
Disk Surface ◽  
Flying Height ◽  
Trailing Edge ◽  
Detailed Measurement ◽  
Head Slider ◽  
Pitch Frequency ◽  
Two Degree Of Freedom

We experimentally and theoretically investigated in detail bouncing vibrations of a flying head slider in the near-contact region between the head and disk surface. By changing the Z-height in the experiment, we evaluated the effect of the pitch static angle on the ambient pressure at which unstable bouncing vibration starts and stops. We found that the touch-down and take-off pressure hysteresis decreased as the pitch static angle increased even though the flying height at the trailing edge decreased slightly. From detailed measurement of the slider dynamics at the threshold of the bouncing vibration, we found that the trailing edge of the slider was first attracted to the disk. As the pitch static angle decreased, the magnitude of the first drop of the trailing edge increased and the bouncing vibration amplitude increased more rapidly. We also measured the mode of the bouncing vibration by using two laser Doppler vibrometers simultaneously. By using an improved two-degree-of-freedom slider model, in which the small micro-waviness and the shearing force of the lubricant were taken into account, we could analyze the touch-down/take-off hysteresis, mode, and destabilization process of the bouncing vibration similar to the experimental results. We also theoretically found that either self-excited bouncing vibration with lower pitch frequency or forced vibration with higher pitch frequency was generated, depending on the magnitudes of the micro-waviness and the disturbance.

Numerical Investigation of Bouncing Vibrations of an Air Bearing Slider in Near or Partial Contact

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Du Chen ◽  
David B. Bogy
Keyword(s):  
Contact Region ◽  
Hard Disk Drives ◽  
Disk Surface ◽  
Contact Friction ◽  
Asperity Contact ◽  
Air Bearing ◽  
Disk Interface ◽  
Partial Contact ◽  
Adhesion Model ◽  
Air Bearing Slider

Near or partial contact sliders are designed for the areal recording density of 1 Tbit/in.2 or even higher in hard disk drives. The bouncing vibration of an air bearing-slider in near or partial contact with the disk is numerically analyzed using three different nonlinear slider dynamics models. In these three models, the air bearing with contact is modeled either by using the generalized Reynolds equation modified with the Fukui–Kaneko slip correction and a recent second order slip correction for the contact situation, or using nonlinear springs to represent the air bearing. The contact and adhesion between the slider and the disk are considered either through an elastic contact model and an improved intermolecular adhesion model, respectively, or using an Ono–Yamane multi-asperity contact and adhesion model (2007, “Improved Analysis of Unstable Bouncing Vibration and Stabilizing Design of Flying Head Slider in Near-Contact Region,” ASME J. Tribol., 129, pp. 65–74.). The contact friction is calculated by using Coulomb’s law and the contact force. The simulation results from all of these models show that the slider’s bouncing vibration occurs as a forced vibration caused by the moving microwaviness and roughness on the disk surface. The disk surface microwaviness and roughness, which move into the head disk interface as the disk rotates, excite the bouncing vibration of the partial contact slider. The contact, adhesion, and friction between the slider and the disk do not directly cause a bouncing vibration in the absence of disk microwaviness or roughness.

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.

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.

Analysis of Microwaviness-Excited Vibrations of a Flying Head Slider in Asperity Contact Regime

2016 ◽  
Author(s):  
Kyosuke Ono
Keyword(s):  
Hard Disk Drives ◽  
Adhesive Contact ◽  
Flying Height ◽  
Design Parameters ◽  
Lubricant Layer ◽  
Asperity Contact ◽  
Head Slider ◽  
Spacing Variation ◽  
Parameter Values ◽  
Fly Height

The flying height of a head slider in hard disk drives has been decreased close to 1 nm but still must be reduced to ∼0.5 nm in order to increase recording density. At such a narrow spacing, variation in head/disk spacing caused by microwaviness (MW) becomes a significant concern [1]. Some comprehensive numerical simulations of slider dynamics in the near-contact and contact regimes have been conducted [2–5]. However, the real physics behind slider dynamics does not seem to be fully elucidated because the head-disk interfacial force changes with differences in interfacial design conditions such as the air-bearing surface, surface roughness, and lubricant layer. In this study, we evaluated head-disk interfacial forces by asperity adhesive contact theories with measured asperity parameter values. The MW-excited vibrations of a thermal fly-height control (TFC) slider in proximity and asperity contact regimes were simulated by changing the design parameters. It was found that the simulated results allow us to understand typical experimental results reported in previous literature.

Three-Dimensional Measurement of Head Flying Height and Attitude Using Image Processing of Fringe Patterns Formed by Michelson Laser Interferometry

1996 ◽  
Vol 118 (3) ◽  
pp. 564-570 ◽  
Author(s):  
Yasunaga Mitsuya ◽  
Akihito Mitsui ◽  
Yasuyuki Kawabe ◽  
Lars Lunde
Keyword(s):  
Image Processing ◽  
High Speed ◽  
Contact Region ◽  
Three Dimensional ◽  
Ccd Camera ◽  
Laser Interferometry ◽  
Disk Surface ◽  
Flying Height ◽  
Back Surface ◽  
Fringe Patterns

In-situ measurement of head flying height and attitude using image processing of fringe patterns formed by Michelson interferometry is studied. A wide laser beam is applied to illuminate the slider back surface and disk surface simultaneously to create interferometric fringe patterns. Employing the relationships arising between the two fringe patterns, the calculation procedure is formulated to yield the slider’s parallel, pitch and roll displacements. Experimental fringe patterns are captured in a single visual field by a high-speed CCD camera. Image processing for a higher signal-to-noise ratio, such as smoothing, filtering, amplification and ridge line extraction is then applied to the image data. Additionally, average processing with respect to multiple fringe lines to produce higher accuracy is successfully applied. Measured values of flying height and pitch and roll displacements are confirmed to be in good accordance with the calculation results, demonstrating excellent applicability of the present method down to the near-contact region.

Air flow around a magnetic-head-slider suspension and its effect on slider flying-height fluctuation

1990 ◽  
Vol 26 (5) ◽  
pp. 2430-2432 ◽  
Author(s):  
Y. Yamaguchi ◽  
A. Ahasan Talukder ◽  
T. Shibuya ◽  
M. Tokuyama
Keyword(s):  
Air Flow ◽  
Flying Height ◽  
Magnetic Head ◽  
Head Slider
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