Modeling of Amorphous Carbon Overcoat for Investigation of Lubricant Transfer at the Head-Disk Interface

2014 ◽  
Author(s):  
Young Woo Seo ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drives ◽  
Intermolecular Forces ◽  
Realistic Model ◽  
Coarse Grained ◽  
Attractive Potential ◽  
Head Disk Interface ◽  
Carbon Overcoat ◽  
Lubricant Transfer ◽  
Disk Interface ◽  
Dynamics Simulations

In current hard disk drives, the spacing between the slider and the disk is reduced to the order of 1–2 nm. At such a narrow spacing, intermolecular forces at the head-disk interface play an important role in achieving a stable slider-disk interface. Even in the absence of actual head-disk contact, lubricant transfer between a slider and a disk may occur. Transferred lubricant can change the flying characteristics of the slider in subsequent read-write operations. It is therefore apparent that lubricant transfer at the head-disk interface is undesirable. In this paper, molecular dynamics simulations were performed to investigate lubricant transfer between a slider and a disk. A so-called coarse-grained bead spring (CGBS) model was implemented. In this model, the Lennard-Jones potential, the short-range polar attractive potential, and the finitely extensible nonlinear elastic potential functions were used to describe the intermolecular interactions at the head-disk interface. Also, in order to develop a realistic model of the carbon overcoat, different modeling approaches are discussed, including the use of rigid coarse-grained beads and a 3-body Tersoff potential function.

On the Touchdown-Takeoff Hysteresis Observed at the Head-Disk Interface in Hard Disk Drives

2005 ◽  
Author(s):  
Rohit P. Ambekar ◽  
David B. Bogy
Keyword(s):  
Experimental Approach ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Intermolecular Forces ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Contributing Factors ◽  
Factors Affecting ◽  
Disk Interface

The touchdown-takeoff velocity hysteresis observed in hard disk drives during CSS or L/UL tests is analyzed using an experimental approach. Tests similar to L/UL were conducted for different slider-disk combinations at different humidities. Factors affecting the touchdown and takeoff velocity were identified on the basis of their domain of operation. It is concluded that the intermolecular forces and meniscus forces are contributing factors to hysteresis, which is also influenced by disk topography and slider dynamics.

Simulation of Contact Behavior of the Thin Film of Hard Disk at Head/Disk Interface

2011 ◽  
Vol 287-290 ◽  
pp. 2339-2342
Author(s):  
Hong Rui Ao ◽  
Deng Pan ◽  
Hong Yuan Jiang
Keyword(s):  
Thin Film ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Hertzian Contact ◽  
Von Mises Stress ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Slider Motion ◽  
Von Mises ◽  
Layered Thin Film

The contact at head/disk interface in hard disk drives subject to an external shock has been studied using the finite element method. A rigid cylinder moving over a two-layered thin film was implemented to simulate the contact between the recording slider and the disk. The effects of different friction coefficients on the von Mises stress of two-layered thin film were investigated. The relation between pressed depth and width of deformation has been obtained. Results show that the amplitude decreases with increase of friction coefficient while the period of slider motion is diminution. In addition, the stress distribution fits Hertzian contact theory.

Molecular Dynamics Simulation of Lubricant Transfer at Head–Disk Interface

2018 ◽  
Vol 2018 (0) ◽  
pp. S1610003
Author(s):  
Kento KAWAI ◽  
Sho WASHIO ◽  
Takayuki KOBAYASHI ◽  
Hedong ZHANG ◽  
Kenji FUKUZAWA ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Head Disk Interface ◽  
Lubricant Transfer ◽  
Disk Interface

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.

scholarly journals Parametric Investigations at the Head-Disk Interface of Thermal Fly-Height Control Sliders in Contact

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Sripathi V. Canchi ◽  
David B. Bogy ◽  
Run-Han Wang ◽  
Aravind N. Murthy
Keyword(s):  
Hard Disk Drives ◽  
Air Bearing ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Surface Design ◽  
Disk Interface ◽  
Height Control ◽  
Experimental Findings ◽  
And Control ◽  
Fly Height

Accurate touchdown power detection is a prerequisite for read-write head-to-disk spacing calibration and control in current hard disk drives, which use the thermal fly-height control slider technology. The slider air bearing surface and head gimbal assembly design have a significant influence on the touchdown behavior, and this paper reports experimental findings to help understand the touchdown process. The dominant modes/frequencies of excitation at touchdown can be significantly different leading to very different touchdown signatures. The pressure under the slider at touchdown and hence the thermal fly-height control efficiency as well as the propensity for lubricant pickup show correlation with touchdown behavior which may be used as metrics for designing sliders with good touchdown behavior. Experiments are devised to measure friction at the head-disk interface of a thermal fly-height control slider actuated into contact. Parametric investigations on the effect of disk roughness, disk lubricant parameters, and air bearing surface design on the friction at the head-disk interface and slider burnishing/wear are conducted and reported.

Boundary Effect on Particle Motion in the Head Disk Interface

2007 ◽  
Author(s):  
Nan Liu ◽  
David B. Bogy
Keyword(s):  
Drag Force ◽  
Particle Motion ◽  
Boundary Effect ◽  
Hard Disk Drives ◽  
Areal Density ◽  
Air Bearing ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Disk Interface

Simulation of particle motion in the Head Disk Interface (HDI) helps to understand the contamination process on a slider, which is critical for achieving higher areal density of hard disk drives. In this study, the boundary effect—the presence of the slider and disk—on particle motion in the HDI is investigated. A correction factor to account for this effect is incorporated into the drag force formula for particles in a flow. A contamination criterion is provided to determine when a particle will contaminate a slider. The contamination profile on a specific Air Bearing Surface is obtained, which compares well with experiments.

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