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.

Friction Force, Contact Resistance, and Lubricant Shear Behavior at the Magnetic Head-Disk Interface During Starting

1997 ◽  
Vol 119 (4) ◽  
pp. 830-839 ◽  
Author(s):  
S. Wang ◽  
K. Komvopoulos
Keyword(s):  
Shear Stress ◽  
Contact Resistance ◽  
Shear Strain ◽  
Friction Force ◽  
Lubricant Film ◽  
Shear Strain Rate ◽  
Head Disk Interface ◽  
The Real ◽  
Disk Interface ◽  
Analysis Scheme

During the starting operation of magnetic rigid disks, a stiction phenomenon characterized by a high friction force may be encountered due to the smoothness of the contacting surfaces and the small thickness of the lubricant film. Since friction measurement using a force transducer yields a signal proportional to the slider displacement, the real friction force at the head-disk interface cannot be measured directly. In the present study, a dynamic data analysis scheme is developed to obtain the real friction force as a function of time based on the measured apparent friction force. Electric contact resistance measurements demonstrate that the transition from static to kinetic friction occurs before the apparent friction force reaches a maximum value. Assuming a constant acceleration of the disk, the relative slip velocity at the contact interface is obtained as a function of time. The relationship between the shear stress and shear strain rate for a relatively thick lubricant film is found to be approximately linear up to a critical value of the shear stress. Due to the extremely high shear strain rates, the maximum real friction force can be significantly greater than the maximum static friction force.

scholarly journals In Situ Measurement of Seeking Speed and Seeking Induced Head-Disk Interface Instability in Hard Disk Drives

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Yu Wang ◽  
Xiongfei Wei ◽  
Yanyang Zi ◽  
Kwok-Leung Tsui
Keyword(s):  
High Speed ◽  
Hard Disk Drives ◽  
Laser Doppler Vibrometer ◽  
Voice Coil Motor ◽  
In Situ Measurement ◽  
Head Disk Interface ◽  
Magnetic Head ◽  
Interface Instability ◽  
Disk Interface

This paper investigated the instability of head-disk interface caused by the voice coil motor (VCM) end crashing the crash stop during the seeking of magnetic head. To make the whole process of that clear, an in situ measurement method based on maximum likelihood estimation and extended Kalman filter for seeking speed at component level was developed first and was then calibrated by a high speed camera. Given a crash between VCM end and crash stop that may be a consequence of the continuous increasing seeking speed, the seeking speed was carefully controlled by using our developed method to find a critical value that may induce vigorous head-disk interface instability. Acoustic emission sensor and laser Doppler vibrometer were used to capture the transient dynamic behaviors of magnetic head when the crash is happening. Damage analysis and mode identification were carried out to reveal the relationship between the damage patterns on disk surface and head dynamics. The results of this study are helpful to optimize the track seeking profile during the HDD operation, as well as the design of components such as head and head arm.

Sliding Failure Model for Magnetic Head-Disk Interface

1990 ◽  
Vol 112 (2) ◽  
pp. 299-303 ◽  
Author(s):  
P. A. Engel ◽  
B. Bhushan
Keyword(s):  
Friction And Wear ◽  
Time To Failure ◽  
Failure Model ◽  
Head Disk Interface ◽  
Magnetic Head ◽  
Disk Interface ◽  
Damage Rate ◽  
Debris Particles ◽  
Physical Variables ◽  
Topographic Parameters

A mechanical model is presented for the “time to failure” of a sliding magnetic head-disk interface system. The principal physical variables include the sliding speed, surface topography, elastic mechanical properties, coefficient of friction, and wear rate. Surface protrusions, such as asperities and debris particles, induce impact and sliding encounters which represent a damage rate. Failure occurs when a specific damage rate, a characteristic for the system, is reached. Modeling uses a set of topographic parameters describing the changing, wearing surface.

Contact analysis of laser textured disks in magnetic head–disk interface

Wear ◽  
1999 ◽  
Vol 230 (1) ◽  
pp. 11-23 ◽  
Author(s):  
Sameera Chilamakuri ◽  
Bharat Bhushan
Keyword(s):  
Contact Analysis ◽  
Head Disk Interface ◽  
Magnetic Head ◽  
Disk Interface

Effect of particulate contamination on the friction and wear of a magnetic head-rigid disk interface

2000 ◽  
Vol 214 (5) ◽  
pp. 493-505 ◽  
Author(s):  
S Chandra ◽  
B Bhushan
Keyword(s):  
Failure Mechanism ◽  
Friction And Wear ◽  
Particle Concentration ◽  
Damage Mechanism ◽  
Flying Height ◽  
Head Disk Interface ◽  
Magnetic Head ◽  
Disk Interface ◽  
Particulate Contamination ◽  
Rigid Disks

Particulate contamination studies were carried out with laser-textured and mechanically textured magnetic rigid disks and nanosliders. The effects of particle concentration and its size, particle material, duration of exposure to contamination, interface speed and disk textures were studied. The head-disk interface (HDI) durability increased as particle concentration decreased. The effect of different hard-particle materials was attributed to how easily it can form agglomerates. Data indicate that limited-time exposure to a class 10 000 environment will not deter tribological performance of the HDI. In a contaminated environment, head flying in the data zone exhibited higher durability than that in the-lase textured zone. However, the mechanically textured disk and the data zone of laser-textured disks showed comparable durability in the presence of contamination. The HDI damage mechanism and pattern changed as the disk speed changed. A failure mechanism to show how the airborne particles interact with the interface is presented. The effects of the HDI geometry, flying height, pitch angle which controls the air flow pattern govern the failure mechanism in the flying mode.

Contact Analysis of Regular Patterned Rough Surfaces in Magnetic Recording

1995 ◽  
Vol 117 (1) ◽  
pp. 26-33 ◽  
Author(s):  
Bharat Bhushan ◽  
Xuefeng Tian
Keyword(s):  
Thin Film ◽  
Rough Surface ◽  
Optimum Design ◽  
Contact Area ◽  
Magnetic Recording ◽  
Design Criteria ◽  
Head Disk Interface ◽  
Magnetic Head ◽  
Disk Interface ◽  
Meniscus Force

The contact of regular patterned rough surface in magnetic recording was analyzed to predict the contact area, meniscus force and permissible load under thin-film lubricated conditions. The contact area, the meniscus force, and the permissible load at the magnetic head-disk interface were studied as a function of the shape, size and the occupation of asperities. Optimum design criteria for both constant occupation and nonconstant occupation of identical asperities were developed to design future magnetic head and disk surfaces.

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