Download or read book Investigation of the Effect of Shock Vibration Surface Texture and Surface Pattern on the Dynamics of the Head Disk Interface written by Aravind N. Murthy and published by . This book was released on 2007 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical methods were used to study the effect of shock and vibrations on hard disk drives. Finite element models of the hard disk drive were developed for the operational and non-operational state of the drive for three different form factors. The numerical results were compared and validated with experimental data. A commercially available non-linear finite element solver was used to obtain the structural response of the hard disk drive components subject to external shock and vibration inputs. A finite element solution of the Reynolds equation was used to investigate the air bearing response of the head disk interface. The inclusion of surface texture and surface pattern on the slider air bearing surface and its effect on slider flying characteristics were studied.

Download or read book Numerical Investigation of the Effects of Operational Shock and Disk Surface Pattern on the Dynamics of Head Disk Interface in Hard Disk Drives written by Liping Li and published by . This book was released on 2013 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation investigates the effects of shock and the disk surface pattern on the head disk interface (HDI) response in hard disk drives (HDDs). A new local adaptive mesh method is proposed at the end to improve the accuracy and efficiency of the algorithm to simulate the sliders' steady flying attitudes. Over the past decades, there has been an increase in the demand of HDDs used in portable devices. In such applications, the work performance of a HDD mainly depends on its ability to withstand external disturbances. Studies of the HDD's responses and failures during external shocks can be very beneficial for improving the HDD's design. A multi-body operational shock (op-shock) model is developed for this purpose in this thesis. The Guyan reduction method is used to model all the components considered in the op-shock model (a disk, a spindle motor, a base plate, a pivot and a head actuator assembly (HAA)). A fluid dynamic bearing (FDB), between the rotating and stationary units in the spindle motor, is simplified as a spring-dashpot system to save computation efforts. The same simplification is applied to a ball bearing (BB) system between the rotating and stationary units in the actuator pivot. Then the reduced models for all the components are assembled to obtain a complete multi-body op-shock model. Four models which include different components are introduced in this thesis to investigate various components' effects on the HDD's operating performance. The HDDs' failure mechanisms are also studied. It is found that different components influence the HDI responses in different ways. The ramp load/unload (LUL) technology has been proved to be a better alternative to the contact start-stop (CSS) approach due to the advantages of increasing areal density and greater durability. However, the application of the LUL ramps in the HDDs increases the possibility of collisions between the disk and the ramps since the ramps sit closely to the disk's outer radius. Therefore, it is important to study the ramp effects on the HDD's response during a shock. A reduced model of a deformable ramp is developed and implemented to the multi-body op-shock model. Numerical analyses using three ramp models (no-ramp model, rigid ramp model and deformable ramp model) are carried out to study the HDD's failure dependence on different ramp models. Bit patterned media (BPM) recording is one of the promising techniques for future disk drives in order to increase the areal density above 4 Tbit/in2. In patterned media, an individual recorded bit is stored in a distinct magnetic island. Thus, the BPM can change the topography of the disk surface and has an effect on the flying characteristics of the air bearing sliders. Proper designs of sliders and disks in the HDDs are required in order to achieve a stable work performance. So a simulator to model a slider's flying condition over a BPM disk is particularly important. Three methods (the averaging method, the Homogenization method and the Taylor expansion Homogenization methods) are implemented to simulate a slider's flying attitude, and finally an economical accurate method is chosen (the Taylor expansion Homogenization method) to investigate the slider's dynamics on partially planarized patterned media. In modern HDDs, the requirement of small and steady head disk spacing leads to more complicated air bearing surface designs. Thus it is challenging for an air bearing simulator to accurately capture the pressure under a slider's surface. A new local adaptive grid-generating algorithm is developed and is used to simulate the sliders' steady flying attitude. Local finer meshes (mesh's dimension decreases to half) are created on the nodes of the current grids, which have pressure gradients or geometry gradients larger than a pre-defined tolerance. Two sliders are used to demonstrate the applicability of this method. It is found that this new local adaptive grid-generating method improves the stability and efficiency of the simulation scheme.

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 Numerical and Experimental Investigations of a Hard Disk Drive Subject to Shock and Vibration written by Eric Michael Jayson and published by . This book was released on 2003 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Investigation of Operational Shocks and Vibrations in Mobile Hard Disk Drives written by Rahul Rai and published by . This book was released on 2011 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last decade, there has been a continuous increase in the demand of hard disk drives (HDDs) for the mobile applications. In such devices, HDDs are often subjected to mechanical shocks and vibrations. Such external disturbances can degrade the read/write (R/W) performance of mobile drives and in extreme cases it can even cause the loss of stored magnetic information. Hence the ability of the head-disk interface (HDI) to withstand such excitation becomes critical in determining the reliability of a mobile disk drive. This dissertation presents a simulation method to accurately model the response of a mobile HDD to external disturbances which can aid the design process. A numerical investigation was conducted on a 2.5 inch form factor laptop drive to understand the dynamics of the HDI during dynamic events such as operational shocks. A detailed model for the mobile disk drive was developed which includes a spinning disk, a fluid dynamic bearing (FDB) based spindle motor, a base plate and an actuator. The behavior of the HDI subjected to various disturbances was determined by solving a fluid-structure interaction problem in which a spinning disk and a head (slider) were coupled through an air bearing. Case studies were conducted to determine the effect of parameters like shock pulse width, HDD orientation, parking ramp contact and FDB dynamic coefficients on the performance of a HDD during the excitation. It was observed that the proximity of the pulse to the HDD component's natural frequencies has an adverse effect on the shock resistance of the HDI. Furthermore, the orientation of the HDD during the shock can also affect the stability of the HDI. In the case of planar excitations, the FDB dynamics becomes critical in determining the slider's vibration amplitude. This knowledge about the HDI failure mechanism and its vibration characteristics can be helpful in designing a mobile HDD with a better shock performance.

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1992 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Numerical and Experimental Investigation of the Head disk Interface written by Michael H. Wahl and published by . This book was released on 1994 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Study of Dynamics and Nanoscale Heat Transfer of Head Disk Interface in Hard Disk Drives written by Yuan Ma and published by . This book was released on 2018 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its introduction in 1956, hard disk drives have become one of the dominant products in the industry of data storage. The capacity of the hard disk drives must keep evolving to store the exploding data generated in the era of big data. This demand pushes the development of technologies including heat assisted magnetic recording (HAMR), microwave assisted magnetic recording (MAMR) and bit-patterned media (BPM) to increase the areal density beyond 1Tb/in2. In the development of these technologies, it is essential to have a clear understanding of the dynamics and nanoscale heat transfer behavior across the head-disk interface. In this dissertation, dynamics and nano-scale heat transfer in the head disk interface are discussed. Experimental study of nano-scale heat transfer is conducted with the specifically designed static touchdown experiment. Simulation strategy that incorporates the wave-based phonon conduction theory was also developed. In the flying condition, correlation between the temperature and head disk spacing was found at both passive flying stage and modulation stage. When the flying height increases due to either disk surface microwaviness or contact induced modulation, head temperature will increase, with a slight time delay, indicating the existence of a cooling effect as the head approaches the disk. The static touchdown experiment, which decouples the complicated air bearing from the nano-scale interface was further designed and performed. The heat transfer behavior across a closing nano-scale gap between head and disk was observed and measured. Experimental and simulation results showed general agreement with the theoretical predictions of the wave based theory for radiation and phonon conduction. The effect of different factors including humidity, air pressure, lubricant layer and disk substrate in the static touchdown experiment were also studied separately. Furthermore, the dynamics of HAMR condition was studied with waveguide heads. The laser induced protrusion was found to be around 1~2 nm in height. The findings of this dissertation could be applied to future HAMR head/media design, and the static touchdown experiment could be potentially improved to be a new approach to measure material conduction coefficient and emissivity with high special resolution.

Download or read book Journal of Lubrication Technology written by and published by . This book was released on 1996 with total page 946 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of the Head Disk Interface in Heat Assisted Magnetic Recording Energy and Mass Transfer in Nanoscale written by Haoyu Wu and published by . This book was released on 2018 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hard disk drive (HDD) is still the dominant technology in digital data storage due to its cost efficiency and long term reliability compared with other forms of data storage devices. The HDDs are widely used in personal computing, gaming devices, cloud services, data centers, surveillance, etc. Because the superparamagnetic limit of perpendicular magnetic recording (PMR) has been reached at the data density of about 1 Tb/in^2 , heat assisted magnetic recording (HAMR) is being pursued and is expected to help increase the areal density to over 10 Tb/in^2 in HDDs in order to fulfill the future worldwide data storage demands. In HAMR, the magnetic media is heated locally (~50nm x 50nm) and momentarily (~10ns) to its Curie temperature (~750K) by a laser beam. The laser beam is generated by a laser diode (LD) and focused by a near field transducer (NFT). But the energy and mass transfer at high temperature from the laser heating can cause potential reliability issues. The design temperature of the NFT is much lower than the media’s Curie temperature. However, the distance between the NFT and the media is less than 10nm. As a result, the heat can flow back from the media to the NFT, which is called the back-heating effect. This can cause undesired additional temperature increase on the NFT, shortening its lifetime. Additionally, depletion, evaporation and degradation can happen on the lubricant and the carbon overcoat (COC) layer of the media. The material can transfer from the media to the head at high temperature and cause solid contamination on the head, adversely affecting its reliability. Since the laser heating in HAMR happens at nanoscale spatially and temporally, it is difficult to measure experimentally. In this dissertation, a comprehensive experimental stage, called the Computer Mechanics Laboratory (CML)-HAMR stage, was built to study different aspects of HAMR systems, including the heat and mass transfer in the head-disk interface during laser heating. The CML-HAMR stage includes an optical module, a spinstand module and a signal generation/acquisition module. And it can emulate the HAMR scenario. The head’s temperature was measured during the laser heating using the stage and heads with an embedded contact sensor (ECS). It was estimated, based on a linear extrapolation, that the ECS temperature rise is 139K, 132K, 127K and 122K when the disk is heated to the Curie temperature (~750K) and the head-disk clearance is 0nm, 1nm, 2nm and 3nm, respectively. The heating effect of the ECS was also studied and a related heat transfer experiment was performed. The normalized ECS self heating temperature rise, an indicator of the heat transfer in the head-disk interface (HDI), was measured. It was concluded that the heat transfer coefficient across the HDI strongly depends on the width of the gap size, especially when the gap size is smaller than 1nm. The head disk interaction during the laser heating was studied using a waveguide head, i.e., a HAMR head without the NFT. It showed that the laser heating can cause head surface protrusion. This lowers the fly-height (FH) and results in early touchdown (TD). It was shown that the ratio of touchdown power (TDP) change to the laser current is 0.3mW/mA. The dynamics of the head also changes during the laser heating. It was found that the magnitude of the 1st-pitch-mode vibration on the head increases over time both in short term and long term. The accumulation of material transferred to the head was also investigated. It was found that the solid contamination caused by the laser heating forms in the center of the waveguide. The round-shaped contamination formed on the head surface after laser heating. Finally the disk lubricant reflow after laser heating was studied. In the experiment, a beam of free space laser shines on the rotating disk at different laser powers, disk rotating speeds and repetitions. Then the disk was examined by an optical surface analyzer (OSA). It was found that 80% of the displaced lubricant recovers within 20 minutes. A simulation was also performed. The experiments and the simulation are in good agreement.

Download or read book Effects of Shock on the Head disk Interface written by A. Miller Allen and published by . This book was released on 1995 with total page 44 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 Dynamic Load Head disk Interactions and Interface Durability in Magnetic Disk Drives written by Ta-Chang Fu and published by . This book was released on 1995 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Shock and Vibration Digest written by and published by . This book was released on 1989 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electrical Electronics Abstracts written by and published by . This book was released on 1997 with total page 2240 pages. Available in PDF, EPUB and Kindle. Book excerpt: