Steady-state Flying Research Articles

Air Bearing Simulation of Discrete Track Recording Media

Sliders flying over patterned or discrete track media are exposed to an entirely different pressure field from the air bearing than in the case of present day "smooth" disks. In this first study, we investigate the influence of discrete track media parameters such as groove width, groove pitch, and groove depth on the steady-state flying characteristics of five different slider designs using a finite-element-based air bearing simulator

Slider vibration reduction using slider surface texture

Surface texture with a height of 4.5 nm was fabricated on two types of pico-sliders using argon plasma etching. The nominal flying height of the sliders was 5 and 7 nm, respectively. Laser Doppler vibrometry (LDV) was used to investigate the dynamics of the textured and untextured sliders during steady-state flying and during contact start/stop (CSS). During steady-state flying, the texture was found to significantly reduce both rigid body slider vibration modes and air-bearing modes. During CSS, the amplitude of both out-of-plane and in-plane vibrations was found to be reduced as a consequence of the texture on the slider surfaces.

Optimization of Air Bearing Contours for Shock Performance of a Hard Disk Drive

Hard disk drives must be designed to withstand shock during operation. Large movements of the slider during a shock impulse can cause reading and writing errors, track misregistration, or in extreme cases, damage to the magnetic material and loss of data. The design of the air bearing contour determines the steady-state flying conditions of the slider as well as dynamic flying conditions, including shock response. In this paper a finite element model of the hard disk drive mechanical components was developed to determine the time dependent forces and moments applied to the slider during a shock event. The time-dependent forces and moments are applied as external loads in a solution of the dynamic Reynolds equation to determine the slider response to a shock event. The genetic algorithm was then used to optimize the air bearing contour for optimum shock response while keeping the steady flying conditions constant. The results show substantial differences in the spacing modulation of the head-disk interface after a shock as a function of the design of the air bearing contour.

Dynamics for Micromachined Mother Ship Negative Pressure Slider Bearings With an Integrated Microsuspension Mechanism in Proximity Magnetic Recording

This paper describes head/disk interface dynamics for micromachined mother ship negative pressure slider bearings with an integrated microsuspension mechanism that we proposed, at steady-state flying in proximity magnetic recording. The authors first indicated the analytical model for air bearing dynamics of mother ship slider mechanisms, and the advantages of the mechanisms were discussed from the dynamics points of view, compared with conventional flying head slider mechanisms. Dynamic design considerations and optimization for micromachined mother ship negative pressure slider bearings with an integrated microsuspension mechanism were also investigated. Finite element simulation for the stiffness analysis of a microsuspension mechanism was carried out and the design optimization for low stiffness gimbals was studied. Furthermore, the effects of slider mass ratio and slider car film stiffness ratio of a secondary slider to a primary slider on mother shipslider dynamics were analyzed numerically. Considering those numerical simulationresults, system optimization for sliders as well as microsuspension gimbals was established to achieve head/disk interface reliability in high density proximity magnetic recording.

Tribology of Tri-Pad Sliders©

The tribology of tri-pad sliders is investigated for hydrogenated and nitrogenated carbon overcoated disks. Friction and stiction during contact-start-stop testing are measured for both types of disks and the acoustic emission signal is studied to investigate the modes of slider vibrations during steady-state flying. Finite element simulations of the steady-state slider vibrations are performed and the results are compared with experimental observations. The optical fluorescence spectra are studied for the aluminum oxide and aluminum oxide-titanium-carbide (Al2O3TiC) portions of the slider. In addition, wear of the rear pad of a tri-pad slider is determined for fixed-track testing using nanoindentations. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

A Numerical Scheme for Static and Dynamic Simulation of Subambient Pressure Shaped Rail Sliders

A numerical scheme based on the finite difference technique is developed to simulate the steady-state flying conditions and dynamic responses of subambient pressure sliders with shaped rails. In order to suppress numerical difficulties caused by the clearance discontinuities present in the subambient pressure sliders, the control volume formulation of the linearized generalized lubrication equation is utilized. For the shaped rail sliders, a method of averaging the mass flow across the rail boundaries is implemented. Furthermore, the power-law scheme by Patankar, is implemented in calculating the mass flows. The resulting equation is solved using the alternating direction implicit method. For the simulation of steady-state flying conditions, a variable time step algorithm is implemented for the purpose of reaching the steady-state values as quickly as possible. This numerical scheme is very efficient in that the coarse finite difference mesh is sufficient for numerical stability, and that the time step changer very much improves the convergence rate. The static flying heights of the Transverse Pressure Contour and the “Guppy” slider are calculated for different disk velocities and slider skew angles. For the Guppy slider, the dynamic responses of the slider to a cosine bump and disk runout are simulated.

Evaluation of capacitance displacement sensors used for slider-disk spacing measurements in magnetic disk drives

In a previous work, the authors (1991) compared head-disk spacing measurements in a magnetic hard disk drive that were made by a multichannel laser interferometer (MCLI) with those made simultaneously by capacitance probes (CP) embedded the air bearing surfaces of the slider. The flying height was determined through the contact-start-stop (CSS) process by averaging the spacing over one disk revolution during steady-state flying. In the present work, the authors show why a different calibration of the CP is needed for flying height and spacing variation measurements, and they derive an expression that gives the calibration factor as a function of the relative length of the CP to the slider's length. They also explain why the CP measurement appears to give an erroneous dependence of spacing variation on flying height.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Comparison of flying height measurement between multi-channel laser interferometer and the capacitance probe slider

The authors studied the dynamics of a capacitance probe slider by measuring the head-disk spacing during CSS (contact-start-stop) cycles and during steady-state flying. They measured the head-disk spacing with both the MCLI and the capacitance probe slider simultaneously and then attempted to correlate the spacing fluctuation results. They first determined the calibration factor by measuring the flying height and the change in the capacitance during the CSS cycle. As expected, it was observed that the change in the capacitance is a nonlinear function of the change in the spacing. However, it was also discovered that the same calibration factor determined by a CSS cycle cannot be applied to calibrate the spacing fluctuation measurements made during steady-state flying conditions. The disagreement is due to spacing averaging caused by the finite size of the capacitance pad. >

Modeling the Flying Characteristics of a Rough Magnetic Head Over a Rough Rigid-Disk Surface

The volumetric information storage density of rigid disk drives continues to increase through decreases in the slider-disk separation (i.e., the flying height). Reductions in slider-disk separations are achieved primarily through smoother surfaces on the magnetic media. The limiting factor in decreasing the slider-disk separation is the interactions that occur between the slider and the diminishing surface roughness and the impact that this roughness has on the transient and steady-state flying characteristics of the recording head. In this paper, we present a new finite element algorithm to solve the modified Reynolds equation that is specifically designed to utilize state of the art vector/parallel hardware. To the authors’ knowledge, this is the first numerical simulation of the flying characteristics of a finite width slider over a rigid disk surface which directly incorporates three-dimensional surface roughness. The effects that the magnitude, orientation, shape, and location (i.e., roughness on the disk or slider) of the surface roughness has on the steady-state slider flying characteristics are presented.