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 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 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 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 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 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 Thinning Films and Tribological Interfaces written by D. Dowson and published by Elsevier. This book was released on 2000-09-01 with total page 857 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection of fully peer-reviewed papers were presented at the 26th Leeds-Lyon Tribology Symposium which was held in Leeds, UK, 14-17 September, 1999. The Leeds-Lyon Symposia on Tribology were launched in 1974, and the large number of references to original work published in the Proceedings over many years confirms the quality of the published papers. It also indicates that the volumes have served their purpose and become a recognised feature of the tribological literature. This year's title is 'Thinning Films and Tribological Interfaces', and the papers cover practical applications of tribological solutions in a wide range of situations. The evolution of a full peer review process has been evident for a number of years. An important feature of the Leeds-Lyon Symposia is the presentation of current research findings. This remains an essential feature of the meetings, but for the 26th Symposium authors were invited to submit their papers for review a few weeks in advance of the Symposium. This provided an opportunity to discuss recommendations for modifications with the authors.

Download or read book Tribochemical Study of Hydrogenated and Nitrogenated Carbon Overcoats at the Head Disk Interface in Magnetic Hard Drives written by Xiaohan Yun and published by . This book was released on 1996 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Frontiers of Magnetic Hard Disk Drive Tribology and Technology written by and published by . This book was released on 2003 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Proceedings of Malaysian International Tribology Conference 2015 written by Mariyam Jameelah Binti Ghazali and published by Malaysian Tribology Society. This book was released on 2015-11-16 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: This ebook is a compilation of papers presented at the Malaysian International Tribology Conference 2015 (MITC2015) - Penang, Malaysia on 16 ~ 17 November 2015.

Download or read book Tribological Research and Design for Engineering Systems written by D. Dowson and published by Elsevier. This book was released on 2003-07-17 with total page 941 pages. Available in PDF, EPUB and Kindle. Book excerpt: These papers represent the proceedings from the 29th Leeds-Lyon Symposium on Tribology, 'Tribological Research and Design for Engineering Systems' which was held in September 2002. Over 130 delegates from 18 countries attended the symposium, and the extensive discussions generated over 150 written questions and responses, which are documented at the end of this proceedings volume. There have been many advances in the field of tribology in recent years, with progress being made in the engineering and interaction of surfaces; micro and nano-tribology; elastohydrodynamics; surface films; surface texture; tribochemistry; wear and life prediction; with both experimental and theoretical contributions. These advances were reviewed, and the impact of this understanding on the fundamentals upon total engineering activity in design, manufacture and machine operation were considered. Readership: Scientists and researchers in the field of tribology.

Download or read book Tribology on the Small Scale written by C. Mathew Mate and published by Oxford University Press. This book was released on 2019-08-30 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: Friction, lubrication, adhesion, and wear are prevalent physical phenomena in everyday life and in many key technologies. This book incorporates a bottom-up approach to friction, lubrication, and wear into a versatile textbook on tribology. This is done by focusing on how these tribological phenomena occur on the small scale — the atomic to the micrometer scale — a field often called nanotribology. The book covers the microscopic origins of the common tribological concepts of roughness, elasticity, plasticity, friction coefficients, and wear coefficients. Some macroscale concepts (like elasticity) scale down well to the micro- and atomic-scale, while other macroscale concepts (like hydrodynamic lubrication) do not. In addition, this book also has chapters on topics not typically found in tribology texts: surface energy, surface forces, lubrication in confined spaces, and the atomistic origins of friction and wear. These chapters cover tribological concepts that become increasingly important at the small scale: capillary condensation, disjoining pressure, contact electrification, molecular slippage at interfaces, atomic scale stick-slip, and atomic bond breaking. Throughout the book, numerous examples are provided that show how a nanoscale understanding of tribological phenomena is essential to the proper engineering of important modern technologies such as MEMS, disk drives, and nanoimprinting. For the second edition, all the chapters have been revised and updated to incorporate the most recent advancements in nanoscale tribology. Another important enhancement to the second edition is the addition of problem sets at the end of each chapter.

Download or read book Modern Tribology Handbook Two Volume Set written by Bharat Bhushan and published by CRC Press. This book was released on 2000-12-28 with total page 1760 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent research has led to a deeper understanding of the nature and consequences of interactions between materials on an atomic scale. The results have resonated throughout the field of tribology. For example, new applications require detailed understanding of the tribological process on macro- and microscales and new knowledge guides the rational

Download or read book Principles and Applications of Tribology written by Desmond F. Moore and published by Elsevier. This book was released on 2013-10-22 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: Principles and Applications of Tribology provides a mechanical engineering perspective of the fundamental understanding and applications of tribology. This book is organized into two parts encompassing 16 chapters that cover the principles of friction and different types of lubrication. Chapter 1 deals with the immense scope of tribology and the range of applications in the existing technology, and Chapter 2 is devoted entirely to the evaluation and measurement of surface texture. Chapters 3 to 5 present the fundamental concepts underlying the friction of metals, elastomers, and other materials. The principles of hydrodynamic lubrication are briefly discussed in Chapter 6, and the mechanisms of boundary and elastohydrodynamic lubrication are examined in Chapters 7 and 8. Chapter 9 is a generalized treatise on wear and abrasion phenomena in metals and elastomers, whereas Chapter 10 deals with the internal friction in solids, liquids, and gases. Chapter 11 is an abbreviated yet thorough treatment of experimental methods used in tribological studies. The remaining five chapters in this book are devoted to specific applications, including manufacturing processes, automotive applications, transportation, locomotion, bearing design, and miscellaneous. This book is an ideal source for mechanical engineering students.

Download or read book Proceedings of the Symposium on Interface Tribology Towards 100 Gbit in2 written by C. Singh Bhatia and published by . This book was released on 1999 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1989 with total page 1518 pages. Available in PDF, EPUB and Kindle. Book excerpt: