Soft Particle-Induced Magnetic Erasure Without Physical Damage to the Media

2007 ◽  
Vol 129 (4) ◽  
pp. 729-734 ◽  
Author(s):  
M. Roy ◽  
J. L. Brand
Keyword(s):  
Frictional Heating ◽  
Mechanical Damage ◽  
Soft Particle ◽  
Head Disk Interface ◽  
Physical Damage ◽  
Component Level ◽  
Disk Interface ◽  
Permanent Loss ◽  
The Media ◽  
The Impact

With ever increasing areal density, interactions of particles with a head-disk interface become an ever more important factor impacting the drive reliability. Although particles trapped between the head and the disk could induce mechanical damage to the media resulting in permanent loss of data, data loss has also been observed without any obvious signs of physical damage to the media. We devised a component-level test to study this mode of data erasure on both glass and aluminium media. Our data indicate that the frictional heating associated with contact force between the particle and the disk could lead to permanent loss of data. In addition, we performed investigations to study the impact of air bearing design features, load/unload mechanism, and particle number density on the head disk interface.

Impact of Touchdown Detection on Bit Patterned Media Robustness

2013 ◽  
Author(s):  
Jia-Yang Juang ◽  
Kuan-Te Lin
Keyword(s):  
Areal Density ◽  
Flying Height ◽  
Head Disk Interface ◽  
Bit Patterned Media ◽  
Patterned Media ◽  
Disk Interface ◽  
Recording Process ◽  
Friction Temperature ◽  
The Media ◽  
The Impact

Bit patterned media (BPM) is considered as a revolutionary technology to enable further increase of areal density of magnetic recording beyond 1 Tbits/in2 [1]. Implementing BPM technology, however, significantly increases the complexity of the recording process, but also poses tremendous tribological challenges on the head-disk interface (HDI) [2]. One of the major challenges facing BPM is touchdown detection by thermal flying-height control (TFC), in which a minute heater located near the read/write transducers is used to thermally protrude a small portion of the slider into contact with the disk, and the contact is then detected by directly or indirectly measuring the friction, temperature rise or vibration caused by the contact [3]–[7]. Most recording heads rely on touchdown detection to achieve a desired flying height (FH), which approaches sub-1-nm regime for many of today’s commercial drives. As a result sensitive and accurate touchdown detection is of critical importance for a reliable head-disk interface by reducing contact duration and unnecessary interaction between the slider and the disk. However, the impact of touchdown on the mechanical robustness of the media has not been properly studied.

Analysis of Stresses Induced by Dynamic Load Head-Disk Contacts

1999 ◽  
Vol 122 (1) ◽  
pp. 233-237 ◽  
Author(s):  
Ta-Chang Fu ◽  
David B. Bogy
Keyword(s):  
Dynamic Load ◽  
Maximum Stress ◽  
Radius Of Curvature ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Impact Stress ◽  
Dual Channel ◽  
Average Maximum ◽  
The Impact ◽  
Maximum Contact

The dynamic load head-disk contact induced impact stress was studied. A dual channel LDV was used to measure the head-disk relative motion during impact, and an analytical model incorporating the Hertz theory of impact was developed to quantitatively estimate the impact induced contact force and stress based on the LDV-measured results. 70 percent sliders were used in order to compare the results with our previous study. From the estimated maximum contact stresses and the results of our previous study, it was found that when the average maximum stress was 511 MPa, the head-disk interface did not show any damage after 100,000 cycles of repeated head-disk impacts. When the average maximum stress was 880 MPa, however, 100,000 repeated head-disk impacts caused significant wear of the disk’s overcoat even though a single impact did not cause any observable damage. From the analysis it can be seen that a lower head-disk impact velocity and/or a larger radius of curvature at the contacting corner of the slider result in a smaller head-disk impact stress on the disk. Based on the analyses, we estimated the radius of curvature needed for a 50 percent (Nano) slider and a 30 percent (Pico) slider to have at least 100,000 cycles of dynamic load head-disk interface durability. Such radius of curvature can be realized, for example, by edge-blending the sliders. [S0742-4787(00)02901-5]

Hard-particle-induced physical damage and demagnetization in the head-disk interface

2013 ◽  
Vol 19 (9-10) ◽  
pp. 1313-1317 ◽  
Author(s):  
Jia Zhao ◽  
Shaomin Xiong ◽  
David B. Bogy ◽  
Kun Sun ◽  
Liang Fang
Keyword(s):  
Hard Particle ◽  
Head Disk Interface ◽  
Physical Damage ◽  
Disk Interface

Frictional heating effect on thermal protrusion in head disk interface

2014 ◽  
Vol 20 (8-9) ◽  
pp. 1565-1570 ◽  
Author(s):  
Jianhua Li ◽  
Junguo Xu ◽  
Masaru Furukawa
Keyword(s):  
Frictional Heating ◽  
Heating Effect ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Thermal Protrusion

Correlating the Data on the Mechanical Damage to Mung Bean Seeds under Impact Loading

2012 ◽  
Vol 7 (6) ◽  
Author(s):  
Feizollah Shahbazi ◽  
Saman Valizadeh ◽  
Ali Dolatshaie
Keyword(s):  
Moisture Content ◽  
Impact Velocity ◽  
Mung Bean ◽  
Impact Damage ◽  
Mechanical Damage ◽  
Physical Damage ◽  
Seed Moisture Content ◽  
Mean Values ◽  
The Mean ◽  
The Impact

Mechanical damage of seeds due to harvest, handling, and other processes is an important factor that affects the quality and quaintly of seeds. This study evaluated impact damage to the mung bean seeds with moisture contents of 9.54 to 25% wet basis and subject to impact velocities from 10 to 25 m/s using a laboratory impact damage assessment device. The results showed that impact velocity, moisture content, and the interaction effects of these two variables significantly influenced the percentage physical damage in mung ban seeds (p<0.01). Increasing the impact velocity from 10 to 25 m/s caused a significant (p < 0.05) increase in the mean values of damage from 0.53 to 31.78%. The mean values of physical damage decreased significantly (p < 0.05) by a factor about two (from 22.41 to 11.24%), with increase in the moisture content from 9.54 to 20%. However, by a higher increase in the moisture from 20 to 25%, the mean value of damage showed a non-significant increasing trend. There was an optimum moisture level of 20%, at which seed damage was minimized. An empirical model composed of seed moisture content and velocity of impact developed for accurately describing the percentage of physical damage to mung beans. It was found that the model has provided satisfactory results over the whole set of values for the dependent variable.

Study on soft-particle intrusion in a head/disk interface of load/unload drives

2000 ◽  
Vol 36 (5) ◽  
pp. 2745-2747 ◽  
Author(s):  
Junguo Xu ◽  
H. Tokisue ◽  
Y. Kawakubo
Keyword(s):  
Soft Particle ◽  
Head Disk Interface ◽  
Disk Interface

Survivors, Not Victims

2013 ◽  
Vol 35 (3) ◽  
pp. 17-19
Author(s):  
Tracey Ulcena
Keyword(s):  
Undergraduate Student ◽  
Social Conditions ◽  
Ethnographic Research ◽  
Physical Damage ◽  
The Media ◽  
The Impact

What some people believe about Haiti and the devastating effects of the 2010 earthquake revolves around the coverage in the media. While the media hinted at what was going on after the January 12th earthquake, it was not a completely accurate portrayal of the complex issues that existed in the various tent cities of Port-au-Prince, Haiti. Almost two years later in 2011, almost 500,000 people were still living in unacceptable conditions in scattered parts of the capital. The things that I witnessed firsthand in Port-au-Prince over the summer of 2011 as an undergraduate student conducting ethnographic research speak to the impact that the earthquake has had beyond the physical damage, particularly in terms of social conditions. What I came away with from my research was that making change is not a question of economics but of humanity.

scholarly journals Mechanical damage during harvest and loading affect orange postharvest quality

2015 ◽  
Vol 35 (1) ◽  
pp. 154-162 ◽  
Author(s):  
MARCELA MIRANDA ◽  
POLIANA C. SPRICIGO ◽  
MARCOS D. FERREIRA
Keyword(s):  
Ascorbic Acid ◽  
Mechanical Damage ◽  
Ascorbic Acid Content ◽  
Titratable Acidity ◽  
Soluble Solids ◽  
Postharvest Quality ◽  
Physical Damage ◽  
Peel Color ◽  
Physico Chemical ◽  
The Impact

Brazil is the world’s largest orange producer; however, part of this production is lost during postharvest. This loss can be minimized by controlling incidence of physical damage throughout the harvest and loading operations. Impacts can negatively modify quantitative and qualitative fruits aspects. The main goal of this study was to measure the impact magnitude in two types of harvest (manual and detachment) and during all steps from picking into bags until loading for transport to the processing industry and additionally evaluating, in laboratory, the physico-chemical quality of the fruit subjected to various impacts, similar to those found in the field. In order to evaluate the impact magnitude, an instrumented sphere was used (760 mm, Techmark, Inc, USA). The following physico-chemical parameters were evaluated during 6-days of storage: weight loss, soluble solids contents, titratable acidity, ascorbic acid content, pH, firmness and peel color. The greatest impacts were observed during harvest, during the detachment practice, and when loading and unloading from bulk storage, with average acceleration values between 249.5 and 531.52G. The impact incidence in oranges were responsible for reducing the soluble solids, titratable acidity, ascorbic acid and weight by to 5.5%; 8.7%; 4.6% and 0.5%, respectively, compared to the control. Impacts during harvest and the various pre-industry manipulation steps must be controlled as they interfere in postharvest quality and physiology of ‘Valência’ oranges.

Contact Force and Frictional Heating due to “Large” Particles in the Head Disk Interface

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Xinjiang Shen ◽  
David B. Bogy
Keyword(s):  
Friction Coefficient ◽  
Contact Force ◽  
Contact Region ◽  
Frictional Heating ◽  
Frictional Coefficient ◽  
Movement Pattern ◽  
Contact Forces ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Large Particles

Particles in the head disk interface may cause large contact forces acting on the slider as well as thermal asperities in the read/write signal. This is especially true for the close spacing required for 1Tbit∕in.2. In this paper, a three-body contact model is employed to study the effects of a particle entrapped between a slider and a disk. A criterion for determining a particle’s movement pattern is proposed. The study of particles in the head disk interface shows that large particles are likely to slide between the slider and disk interface, and the particles going through the trailing pad of an air bearing slider cause severe contact forces on the slider and generate large heat sources. The frictional heating study shows that the temperature around the magnetoresistive head increases to about 5°C for a single 200nm particle passing through the trailing pad of the slider. The effects of the particle size, disk material, and friction coefficient are also studied. It is found that the disk and slider materials and the frictional coefficient between the materials largely affect the contact force acting on the slider by an entrapped particle as well as the temperature rise at its contact region. It is also found that the friction coefficient largely affects a particle’s movement pattern in the head disk interface.

Understanding to Read/Write Signal Modulation Due to Lube Droplet at Head Disk Interface

2008 ◽  
Author(s):  
Jianhua Li ◽  
Junguo Xu
Keyword(s):  
High Viscosity ◽  
Head Disk Interface ◽  
Signal Loss ◽  
Signal Modulation ◽  
Damping Force ◽  
Soft Contact ◽  
Disk Interface ◽  
Damping Characteristics ◽  
Contact Impact ◽  
The Impact

To understand the cause of read/write error due to lube accumulation, a model to simulate the slider’s response to “soft contact”, which can occur between a lubricant droplet on the disk and a slider, was developed. The contact impact model is based on the water-hammer pressure model with an additional damping force, where the wave-shock pressure is assumed to function as the soft contact pressure, and the damping force defines the damping characteristics of the impact which are due to the lubricant’s high viscosity. This modeling and simulation are helpful to us in understanding the read/write signal loss due to a lube droplet at head disk interface.

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