Download or read book Some Tribological Aspects of the Hard Disk Drive Head Disk Interface for Quasi Contact Conditions written by YUNG-KAN CHEN and published by . This book was released on 2015 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: The magnetic recording hard disk drive has been one of the most important storage strategies since 1956. Among all storage solutions, hard disk drives possess the unrivaled advantageous combination of storage capacity, speed, reliability and cost over optical strategies and flash memory. Unlike other storage solutions, hard disk drives utilize a mechanical interface to perform the magnetic read/write process, and therefore its success relies heavily on the stability of the head-disk interface (HDI) which is composed of a magnetic transducer carried by an air bearing slider, an air gap of a few nanometers thick, and a disk surface coated with multiple layers of molecularly-thin films. This dissertation addresses the physics of the interface in terms of contact detection, lubricant modulation and wear. Contact detection serves as one of the core requirements in HDI reliability. The writing process demands a strict spacing control, and its accuracy is based on a proper choice of a contact reference from slider dynamics and therefore the heads’ signal. While functioning in a real drive the only feedback signal comes from sensors neighboring the read-write transducer, and a high speed head-disk contact is associated with complex structural responses inherent in an air-bearing/suspension/lubricant system that may not be well explained solely by magnetic signals. Other than studying the slider-disk interaction at a strong interplay stage, this dissertation tackles the contact detection by performing component-level experimental and simulation studies focusing on the dynamics of air-bearing sliders at disk proximity. The slider dynamics detected using laser Doppler vibrometry indicates that a typical head-disk contact can be defined early as in-plane motions of the slider, which is followed by vertical motions at a more engaged contact. This finding confirms and is in parallel with one of the detection schemes used in commercial drives by magnetic signals. Lubricated disk surfaces play an important role in contact characteristics. As the nature of contact involves two mating surfaces, the modulation of disk lubricant films should be investigated to further understand the head-disk contact in addition to the slider dynamics. In this dissertation, the lubricant modulation is studied under various contact conditions with reference to slider dynamics. It is found that lubricant modulation can be directly associated with the slider’s dynamics in a location specific way, and its evolution is likely to affect the slider’s stable back-off fly-height as the contact is retracted. In addition to modulations at contact proximities, the lubricant response to passive flying and continuous contacting conditions are also addressed for different lubricant types and thicknesses. By integrating the observations from slider dynamics and lubricant modulations, we can establish an insightful understanding towards the transition from flying to the onset of contact. Head wear is also a concern when an erroneous contact detection occurs or imperfections from disk surface exists. Typically a protective diamond-like carbon (DLC) layer of thickness 1-2 nm is coated over the area of the reader/writer shields, and this film loss poses a threat to long term reliability. In this dissertation, in-situ methods of monitoring head wear is proposed in two ways. One method is to evaluate the touchdown power variations as a measure of spacing increase by DLC wear, which was verified by using Auger Electron Spectroscopy, and the other method studies the temperature contact sensor response to gauge mechanical wear. The later possesses the advantage of detecting wear without going into actual contact, but it may be affected by the location difference between the touchdown sensor and wear area.

Download or read book Tribological Study of Contact Interfaces in Hard Disk Drives written by Youyi Fu and published by . This book was released on 2016 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: To achieve an areal density of 1 terabits per square inch (1.55 gigabits/mm2) in hard disk drives, the size of magnetic grains in hard disks has been reduced to approximately 7 nm and the spacing between the magnetic head and the disk has been minimized to 1 to 2 nm. At a spacing on the order of 1 to 2 nm between the head and the disk, it is likely that contacts between the magnetic head and the disk occur during reading and writing, causing erasure of data or even failure of the head/disk interface. Wear particles can be generated as a consequence of contacts between slider and disk, and if particles enter the head/disk interface, catastrophic failure of the head/disk interface can occur. To reduce the generation of wear particles and avoid failure of the head/disk interface, it is important to investigate how the tribological performance of all contact interfaces in hard disk drives can be improved. In this dissertation, the tribological performance of the most important contact interfaces in a hard disk drive are investigated with a focus on the generation of wear particles and lubricant migration. First, fretting wear is investigated to study the effect of a diamond-like carbon (DLC) overcoat on wear of the dimple/gimbal interface. A numerical simulation model based on finite element analysis was developed to explain the experimental results. Then, lubricant migration on the air bearing surface and its effect on the head medium spacing (HMS) was investigated as a function of temperature, slider position, and "parking time" of the slider on the ramp. Thereafter, the thermal response of a thermal sensor during contact with asperities on the disk surface was analyzed. The effects of experimental and environmental conditions on the resistance change of the sensor were studied. Finally, experimental and numerical investigations were performed to analyze contact between the suspension lift tab and the ramp in hard disk drives. The voice coil motor current was used to characterize the change of the friction force and the generation of wear debris at the lift tab/ramp interface during load/unload testing. Numerical simulations were performed to analyze how to reduce contact stress between the lift-tab and the ramp. The results of this dissertation will be helpful in improving the tribological performance of hard disk drives.

Download or read book Tribological Investigations of the Head disk Interface of Hard Disk Drives written by Qing Zhao and published by . This book was released on 1999 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tribological Investigations of the Head disk Interface written by Min Yang and published by . This book was released on 1995 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tribological Performance of the Head Disk Interface in Perpendicular Magnetic Recording and Heat Assisted Magnetic Recording written by Tan Duy Trinh and published by . This book was released on 2019 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: International Data Corporation (IDC) estimates that hard disk drives will still be the main storage device for storing digital data in the next 10 years, holding approximately 80% of the data inside data centers. To increase the areal density of hard disk drives, the mechanical spacing between the head and disk surface has decreased to approximately 1nm. At such a small spacing, tribology of the head-disk interface, including head-disk contacts, wear, material buildup, and lubricant transfer, become increasingly more important for the reliability of hard disk drives. In addition to small spacing, heat-assisted magnetic recording (HAMR) technology aims to deliver higher areal density recording by heating up the media surface to a few hundred Celsius degrees, facilitating the writing process. High temperature at the head and disk surfaces cause serious reliability issues for the head-disk interface (HDI). Therefore, understanding of the main factors that affect the reliability of the head-disk interface is an essential task. In this dissertation, the effect of bias voltage and helium environment on the tribological performance of the head-disk interface is investigated. To do this, we first simulated the flying characteristics of the slider as a function of bias voltage in air and helium environment. Thereafter, an experimental study was performed using custom built tester located inside a sealed environmental chamber to study the effect of air and helium on wear and lubricant redistribution at the head-disk interface during load-unload. We investigated the effect of bias voltage and relative humidity on wear, material buildup, and nano-corrosion on the slider surface. Finally, we have studied laser current and laser optical power in heat-assisted magnetic recording as a function of operating radius, head-disk clearance, media design, and their effects on the life-time of the head-disk interface. The results of this dissertation provide guidance for the effect of bias voltage, relative humidity, and helium environment on wear, material buildup, corrosion, and lubricant transfer at the head-disk interface. More importantly, our experimental study in heat-assisted magnetic recording leads to a better understanding of the main factors that cause failure of the HAMR head-disk interface. Our results are important for the improvement of the tribological performance and reliability of perpendicular magnetic recording (PMR) and heat-assisted magnetic recording (HAMR) head-disk interface.

Download or read book Experimental Study of Head disk Interface Dynamics Under the Condition of Near contact Recording for Magnetic Hard Disk Drives written by Mark Joseph Donovan and published by . This book was released on 1995 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Head disk Interface Tribology in the Nanometer Regime written by Jianfeng Xu and published by . This book was released on 2008 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents experimental and theoretical studies of the characteristics of the head/disk interface at very low flying height. The study starts with a discussion of the tribological background of the head/disk interface and presents a review of the literature related to studies of the head/disk interface. Then, mechanical scaling laws for hard disk drives are discussed. Numerical results for failure inception of brittle and ductile hard disks due to high shock levels are presented. An experimental setup for measuring slider dynamics in five degrees-of-freedom (DOF) is presented. This is followed by experimental studies of slider vibrations due to slider/disk contacts. Thereafter, a study of slider vibrations due to write-head induced "thermal" pole-tip-protrusion is presented. Numerical simulations of slider vibrations are compared with experimental results. A method for measuring the magnetic spacing based on the read-back signal is presented. Finally, the results of this thesis are summarized and directions for future research are given.

Download or read book Experimental Studies of the Head disk Interface from a Tribological and Controls Point of View for Flying Heights Below 2 Nm written by Liane M. Matthes and published by . This book was released on 2016 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the introduction of the IBM 305 RAMAC system in 1956, performance and storage capacities of hard disk drives have improved tremendously. To reliably read and write data, the slider must follow the data stored on the magnetic disk closely enough while maintaining a near constant spacing. Currently, the spacing between the recording and the magnetic disk--the flying height--is on the order of 1-2 nm during reading and writing. At such low spacings, intermittent contacts are inevitable, giving rise to wear and degradation of the head-disk interface. Flying heights of 1-2 nm are achieved using thermal flying height control (TFC) technology. TFC recording heads, or TFC sliders, feature thin-film resistive heater elements near the read and write element. Actuating the heater element heats up the nearby material. The material expands due to the heat which causes the slider to (thermally) protrude towards the disk at the location of the read and write element. An increase in heater power increases this protrusion, thus locally reducing the slider flying height. In this dissertation, we focus on experimental investigations of the interface between a TFC slider and a magnetic disk from both a tribological and controls point of view. First, contact and temperature rise between thermal flying height control (TFC) sliders and magnetic disks are studied. Head-disk contact is established by gradually increasing the power input to the resistive heater element of a TFC slider. Laser Doppler vibrometry is employed for studying the dynamics of the vertical gimbal velocity. The gimbal is part of the suspension which the slider is attached to. The temperature rise upon head-disk contact is estimated from the resistance change at the read element via auxiliary calibration measurements. Next, wear of TFC sliders is studied. Head wear was determined by measuring the change in the heater touch-down power before and after wear testing. The touch-down power denotes the power input to the heater of a TFC slider at which the onset of slider-disk contact occurs. After wear testing, selected heads were examined using scanning electron microscopy to identify regions of wear on the write shields. Furthermore, atomic force microscopy images of worn and unworn recording heads were acquired to determine changes in surface roughness. The effect of bonded fraction of the lubricant, relative humidity, and temperature on head wear is investigated. In addition, we study head wear as a function of relative humidity and DC bias voltage applied across the head-disk interface. Wear tests were performed at

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1993 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Journal of Tribology written by and published by . This book was released on 2007 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fundamentals of Fluid Film Lubrication written by Bernard J. Hamrock and published by CRC Press. This book was released on 2004-03-15 with total page 794 pages. Available in PDF, EPUB and Kindle. Book excerpt: Specifically focusing on fluid film, hydrodynamic, and elastohydrodynamic lubrication, this edition studies the most important principles of fluid film lubrication for the correct design of bearings, gears, and rolling operations, and for the prevention of friction and wear in engineering designs. It explains various theories, procedures, and equations for improved solutions to machining challenges. Providing more than 1120 display equations and an introductory section in each chapter, Fundamentals of Fluid Film Lubrication, Second Edition facilitates the analysis of any machine element that uses fluid film lubrication and strengthens understanding of critical design concepts.

Download or read book Thin Films in Tribology written by G. Dalmaz and published by Elsevier. This book was released on 1993-09-06 with total page 763 pages. Available in PDF, EPUB and Kindle. Book excerpt: The tribological properties of relatively moving surfaces are greatly influenced by thin surface films which are of considerable importance in the design of machine components. From Victorian days when working lubricant films were calculated in tens of micrometres, to today when molecular dynamics simulations and even experiments are beginning to look at nanometre, single molecule thick films, the study of surfaces which is the tribologists' challenge has moved to finer and finer scales. The 66 papers in this volume provide reviews across the tribological field with thin films as their theme, giving a comprehensive and concise description on topics ranging from coatings and surface modification to bio-tribology. The articles provide the reader with an outline of their most effective application and potential uses in new technologies. The volume will be of interest not only to research workers and design engineers in the fields of new machine developments and lubrication, but also to engineers and students specialising in tribology.

Download or read book The Tribology Handbook written by Michael J Neale and published by Elsevier. This book was released on 1995-12-15 with total page 577 pages. Available in PDF, EPUB and Kindle. Book excerpt: The renowned reference work is a practical guide to the selection and design of the components of machines and to their lubrication. It has been completely revised for this second edition by leading experts in the area.

Download or read book The Engineering Index Annual written by and published by . This book was released on 1993 with total page 2264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its creation in 1884, Engineering Index has covered virtually every major engineering innovation from around the world. It serves as the historical record of virtually every major engineering innovation of the 20th century. Recent content is a vital resource for current awareness, new production information, technological forecasting and competitive intelligence. The world?s most comprehensive interdisciplinary engineering database, Engineering Index contains over 10.7 million records. Each year, over 500,000 new abstracts are added from over 5,000 scholarly journals, trade magazines, and conference proceedings. Coverage spans over 175 engineering disciplines from over 80 countries. Updated weekly.

Download or read book Handbook of Contact Mechanics written by Valentin L. Popov and published by Springer. This book was released on 2019-04-26 with total page 357 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book contains a structured collection of the complete solutions of all essential axisymmetric contact problems. Based on a systematic distinction regarding the type of contact, the regime of friction and the contact geometry, a multitude of technically relevant contact problems from mechanical engineering, the automotive industry and medical engineering are discussed. In addition to contact problems between isotropic elastic and viscoelastic media, contact problems between transversal-isotropic elastic materials and functionally graded materials are addressed, too. The optimization of the latter is a focus of current research especially in the fields of actuator technology and biomechanics. The book takes into account adhesive effects which allow access to contact-mechanical questions about micro- and nano-electromechanical systems. Solutions of the contact problems include both the relationships between the macroscopic force, displacement and contact length, as well as the stress and displacement fields at the surface and, if appropriate, within the half-space medium. Solutions are always obtained with the simplest available method - usually with the method of dimensionality reduction (MDR) or approaches which use the solution of the non-adhesive normal contact problem to solve the respective contact problem.

Download or read book Liquid Crystals in Biotribology written by Sergey Ermakov and published by Springer. This book was released on 2015-07-11 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes the theoretical and experimental studies confirming the concept of the liquid-crystalline nature of boundary lubrication in synovial joints. It is shown that cholesteric liquid crystals in the synovial liquid play a significant role in the mechanism of intra-articular friction reduction. The results of structural, rheological and tribological research of the creation of artificial synovial liquids containing cholesteric liquid crystals in natural synovial liquids are described. These liquid crystals reproduce the lubrication properties of natural synovia and provide a high chondroprotective efficiency. They were tested in osteoarthritis models and in clinical practice.

Download or read book The Physics of Ultra High Density Magnetic Recording written by M.L. Plumer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: Application-oriented book on magnetic recording, focussing on the underlying physical mechanisms that play crucial roles in medium and transducer development for high areal density disk drives.