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We report on large eddy simulations of the turbulent flow of air in hard disk drives (HDDs) using a commercial CFD code. In particular, we focus on HDD casings in which flow-induced vibrations are reportedly reduced by small geometrical modifications. The modifications investigated are M I: a blocking plate situated between the disks, M2: a spoiler (or deflector) located behind (downstream of) the actuator arm, and M3: a similar deflector upstream of the arm. We observed that M1, M2, and M3 significantly modify the mean flow patterns in the drives. M1 reduces velocity magnitudes in most parts of the drive, the modification of M2 causes flow reversal in regions close to the hub, while M3 causes the shedding of vortices upstream of the actuator arm. Our analysis points to M1 as the best candidate for mitigating the effects of turbulent airflow. This is because M1 is more effective in reducing the root-mean-square velocity fluctuations near the suspension. M1 is also more effective in reducing the pressure fluctuations near the base-plate and suspension region. This reduction, however, is at the cost of approximately 20% higher windage. Finally, we note that M3 has the adverse effects of increasing velocity and pressure fluctuations and hence is not the ideal candidate for mitigating airflow effects, among the modifications considered here.

We apply the dynamic simulation and modal analysis method to analyze the dynamic properties of slider-air bearings. First, the theoretical background and proposed methods are described. Then, five basic types, one of which is first proposed in this paper, of the air bearing surfaces (ABS) are briefly discussed. The dynamic properties of the sliders are investigated, and compared with each other. It is found that a negative pressure slider has the highest stiffness and lowest damping, the TPC and two newly proposed sliders demonstrate higher damping. Finally, the general ABS design problem is briefly discussed. A new advanced slider is designed, analyzed, and compared with the other sliders. The air bearing of the new slider design has larger stiffness and the highest damping of those studied.

Presents information on a study that examined the production of carbon dioxide from the sliding interface of a carbon-coated thin-film magnetic recording disk. Methodology of the study; Results and discussion on the study.

Focuses on a study which investigated diamond nucleation on unscratched silicon substrates using a conventional microwave plasma-enhanced chemical vapor deposition system. Effect of pretreatment process parameters on diamond nucleation; Methodology of the study; Results and discussion.

Investigates diamond nucleation on very smooth (100) silicon substrates coated with thin films of a colloidal graphite suspension with a microwave-plasma-enhanced chemical-vapor-deposition system. Experimental procedures; Results and discussion.

Deals with a study which investigated the effects of substrate temperature on chemical structure of amorphous carbon films. Background to the study; Experimental procedure; Structure of the microcrystallites.

The air bearing forces of 'pico negative pressure' (1.25 x 1.0 mm subambient pressure) sliders during the unload process were investigated experimentally. A high speed vertical load/unload mechanism with a sensitive force transducer was developed to measure the air bearing forces. Force histories were measured at various disk rpm and unload velocities. The force histories showed that the suspension load dimple separated from the load beam during the lifting. This separation was held to an acceptable amount by flexure limitors built into the suspension. Force-displacement curves show the need for control of the gap between the limitor and load beam. A technique was developed to determine critical suspension parameters for use in the CML Dynamic Load/Unload Simulator. Simulation of the force history was then in excellent agreement with experimental results. Both simulation and experimental results showed that the lift-off force decreases with increasing disk rpm. Experimental results also showed that higher unload speeds lead to larger lift-off forces. By selecting the correct disk rpm and unload speed, the lift-off force could be minimized. [S0742-4787(00)00103-X]

Unstructured adaptive triangular mesh generation techniques and vertex based finite volume schemes that suit slider air bearing simulation of hard disk drives are constructed and implemented. Different refinement and adaptation techniques are used to generate several levels of good quality mesh over sliders with complex rail shapes. At each level either one geometrical or one physical property of the problem is captured. A group of implicit vertex based finite volume schemes is first constructed. The resulting simultaneous linear algebraic equations are solved iteratively by the Gauss-Seidel method. Unconditional stability of the scheme is achieved. In addition, we present a non-nested full approximation storage (FAS) multi-grid algorithm that can significantly speed up the convergence rate of the implicit finite volume schemes. The steady state flying attitude is obtained by a quasi-Newton iteration method. [S0742-4787(00)01804-X]

The mathematical models are critical for accurate simulation of the dynamic load/unload (L/UL) process in disk drives. The air bearing slider and the suspension are the most important parts in the L/UL mechanism. The air bearing modeling has been well researched, but an adequate and efficient suspension model is not available. A simplified 4-DOF suspension model is proposed in this paper. In this model the slider' s pitch angle change due to the motion of the L/UL tab on the ramp is included in the simulation, and the forces applied by the ramp can be directly obtained. The effects of the suspension inertia are included in the effective inertia moments of the slider to improve the loading simulation. The model is implemented and applied to simulate the L/UL process of a pico slider that has been used in recent IBM mobile drives. The effects of the pitch static attitude (PSA), the roll static attitude (RSA), and some initial disturbances to the loading process are investigated. It is found that a positive PSA can significantly smoothen the loading process. The effects of the PSA, the disk rpm, and the unload velocity on the unloading process are also simulated, and it is found that a positive PSA can also greatly improve the unloading performance of the slider. The results show that the unloading process can be accurately simulated by using the proposed model and the loading process can be more accurately simulated by using this 4-DOF model than the 3-DOF model.

Three different mesh refinement and adaptation techniques based on the Delaunay method are used to generate quality unstructured triangular meshes over air-bearing sliders with complicated rail systems. A fully implicit finite volume scheme is formulated to locally integrate the generalized Reynolds equation. The resulting simultaneous equations are solved by point Gauss-Seidel iterations. The scheme is unconditionally stable. The efficiency of the scheme is greatly improved by the implementation of a non-nested multi-grid technique. Index Terms--Air bearing simulation, Delaunay method, finite volume scheme, mesh refinement and adaptation, non-nested multi-grid technique.

Contacts between sliders and disks occur during normal operation in almost all current disk drives, and they can result in undesirable head crash, wear failure, power consumption, or disturbance of the MR read-back signal. The acoustic emission (AE) method has been extensively utilized in the industry to detect these contacts and even to measure the contact force, but a suitable calibration for the AE measurement channel is lacking. Here, we propose two methods for obtaining an in-situ calibration of the AE channel based on simultaneous Laser Doppler Vibrometer (LDV) measurements. One is the force identification method, from which one can obtain the impact force after the AE channel is calibrated. Another is the filter method, from which one can obtain the velocity responses of the slider from AE. The two methods are successfully applied to quantitatively evaluate contact force. Index Terms--Acoustic Emission (AE), calibration method, contact detection, head-disk interface.