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

1991 ◽  
Vol 113 (4) ◽  
pp. 739-749 ◽  
Author(s):  
R. M. Crone ◽  
M. S. Jhon ◽  
B. Bhushan ◽  
T. E. Karis
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Three Dimensional ◽  
Disk Surface ◽  
Information Storage ◽  
Flying Height ◽  
Limiting Factor ◽  
Finite Width ◽  
Rigid Disk ◽  
The Impact

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.

scholarly journals Biomechanical evaluation between orthodontic attachment and three different materials after various surface treatments: A three-dimensional optical profilometry analysis

2019 ◽  
Vol 89 (5) ◽  
pp. 742-750
Author(s):  
İrem Kurt ◽  
Zafer Cavit Çehreli ◽  
Ayça Arman Özçırpıcı ◽  
Çağla Şar
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Material Surface ◽  
Original Material ◽  
Average Surface Roughness ◽  
Average Surface ◽  
Diamond Bur ◽  
Monolithic Zirconia ◽  
Feldspathic Porcelain ◽  
The Impact

ABSTRACT Objectives: To determine the best bonding method of orthodontic attachment among monolithic zirconia, feldspathic porcelain, hybrid porcelain, and the impact of surface-conditioning methods using a three-dimensional optical profilometer after debonding. Materials and Methods: 56 feldspathic porcelain, 56 monolithic zirconia, and 56 hybrid porcelain samples were divided into four surface treatment subgroups: (1) hydrofluoric (HF) acid etch + silane, (2) Al2O3 sandblasting + silane, (3) silicoating (SiO2), and (4) diamond bur + silane. The specimens were tested to evaluate shear bond strength (SBS). Residual composite was removed after debonding. Three-dimensional white-light interferometry was used to obtain quantitative measurements on surface roughness. Results: The highest SBS value was found for the HF acid–etched feldspathic porcelain group. The average surface roughness values were significantly higher in all material groups in which diamond bur was applied, while roughening with Cojet provided average surface roughness values closer to the original material surface. Conclusions: Variations in structures of the materials and roughening techniques affected the SBS and surface roughness findings.

A Quasi-Static Mechanics Analysis of Three-Dimensional Nanoscale Surface Polishing

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
H. Xu ◽  
K. Komvopoulos
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Three Dimensional ◽  
Polished Surface ◽  
Elastic Plastic ◽  
Surface Polishing ◽  
Mechanics Analysis

A quasi-static mechanics analysis of nanoscale surface polishing that provides insight into the surface topography evolution and the removal of material at the asperity level is presented. The analysis is based on a three-dimensional stochastic model that accounts for multiscale (fractal) surface roughness and elastic, elastic-plastic, and fully plastic asperity deformation by hard abrasive nanoparticles embedded in the soft surface layer of a rigid polishing plate. Numerical results of the steady-state roughness of the polished surface, material removal rate, and wear coefficient are presented in terms of the apparent contact pressure, polishing speed, original topography and mechanical properties of the polished surface, average size and density of nanoparticles, and surface roughness of the polishing plate. Simulation trends are associated with elastic-plastic and fully plastic asperity contacts, responsible for irreversible topography changes (roughening effect) and material removal (smoothening effect), respectively. Analytical trends and predictions of the steady-state roughness of the polished surface and material removal rate are shown to be in good agreement with experimental results of nanoscale surface polishing (lapping) of magnetic recording ceramic heads.

Numerical Investigations on Influence of Uniform Blade Surface Roughness on the Performance Characteristics of a Transonic Axial Flow Compressor Stage

2017 ◽  
Author(s):  
Ravi J. Chotalia ◽  
Dilipkumar Bhanudasji Alone
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Axial Flow ◽  
Performance Degradation ◽  
Aviation Industry ◽  
Compressor Stage ◽  
Blade Surface ◽  
Axial Flow Compressor ◽  
Flow Compressor ◽  
The Impact

Application of surface roughness to rotating mechanical bodies will result into performance degradation. In Aviation Industry, one of the most affecting causes for performance or efficiency degradation of gas turbine engine is the blade surface roughness. The aerosols which are very small particles in the atmosphere having diameters in the microns, impinges to the compressor blade inside the aircraft engine at higher altitudes. The aerosols damages surfaces of the compressor blades. Despite of having small dimensions, due to higher velocity of the aircraft, aerosol’s impinging creates roughened surfaces and fouling. This paper is an attempt to numerically evaluate the performance degradation of the single stage transonic axial flow compressor due to uniform roughness created by the aerosols. Various cases with different roughness on various sections of the blades are analyzed to study and identify which section of the blade is more influenced by roughness. The transonic axial flow compressor has a capability of producing 1.36 stage total pressure ratio, swallowing air mass flow rate of 23 kg/s at rated design speed of 12930 rpm is used for the steady state numerical analysis. A systematic steady state 3-dimensional numerical study using solver with SST k-ω turbulence model has been carried out to evaluate the impact of blade surface roughness on the performance of compressor stage. Moreover, cases with the aerosols having different dimensions and their resulting effect is also studied to find out how performance varies when the aircraft enters into atmosphere having big aerosols from the atmosphere having smaller one and vice-e-versa.

Role of disk surface roughness on slider flying height and air-bearing frequency

1990 ◽  
Vol 26 (5) ◽  
pp. 2493-2495 ◽  
Author(s):  
M. Suk ◽  
B. Bhushan ◽  
D.B. Bogy
Keyword(s):  
Surface Roughness ◽  
Disk Surface ◽  
Flying Height ◽  
Air Bearing

Three-Dimensional Measurement of Head Flying Height and Attitude Using Image Processing of Fringe Patterns Formed by Michelson Laser Interferometry

1996 ◽  
Vol 118 (3) ◽  
pp. 564-570 ◽  
Author(s):  
Yasunaga Mitsuya ◽  
Akihito Mitsui ◽  
Yasuyuki Kawabe ◽  
Lars Lunde
Keyword(s):  
Image Processing ◽  
High Speed ◽  
Contact Region ◽  
Three Dimensional ◽  
Ccd Camera ◽  
Laser Interferometry ◽  
Disk Surface ◽  
Flying Height ◽  
Back Surface ◽  
Fringe Patterns

In-situ measurement of head flying height and attitude using image processing of fringe patterns formed by Michelson interferometry is studied. A wide laser beam is applied to illuminate the slider back surface and disk surface simultaneously to create interferometric fringe patterns. Employing the relationships arising between the two fringe patterns, the calculation procedure is formulated to yield the slider’s parallel, pitch and roll displacements. Experimental fringe patterns are captured in a single visual field by a high-speed CCD camera. Image processing for a higher signal-to-noise ratio, such as smoothing, filtering, amplification and ridge line extraction is then applied to the image data. Additionally, average processing with respect to multiple fringe lines to produce higher accuracy is successfully applied. Measured values of flying height and pitch and roll displacements are confirmed to be in good accordance with the calculation results, demonstrating excellent applicability of the present method down to the near-contact region.

Virtual Valve Design for Three Dimensional Numerical Simulations of a Large-Bore Natural Gas Engine

2003 ◽  
Author(s):  
Gi-Heon Kim ◽  
Allan T. Kirkpatrick ◽  
Charles E. Mitchell
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Numerical Models ◽  
Three Dimensional ◽  
Injection System ◽  
Limiting Factor ◽  
Mixing Enhancement ◽  
Length Scales ◽  
Poppet Valve ◽  
The Impact

One of the promising mixing enhancement technologies for natural gas engines currently used is high pressure fuel injection. Three dimensional computational simulations that can examine the entire injection and mixing process in engines using high pressure injection and determine the impact of injector design on engine performance are consequently of considerable interest. However, the cost of three dimensional engine simulations including a moving piston and the kinetics of combustion and pollutants production quickly becomes considerable in terms of simulation time requirements. The limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be two orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a compatible virtual valve which can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated. Downstream flow characteristics of the jets from an actual valve and a virtual valve were compared. Various mixing parameters were evaluated in moving piston simulations that include the effect of the jet-piston interaction. Comparison of the results indicated that it is possible to design a simple converging-diverging fuel nozzle that will produce the same jet and subsequently the same large and turbulent scale mixing patterns as a real poppet valve.

Evolution of Transferred Lubricant Distributions on the Slider Surface Under Ambient and Laser-Heating Conditions

2019 ◽  
Author(s):  
Ryan W. Hetzel ◽  
Shao Wang ◽  
Jonathon R. Lawry ◽  
Ahmed H. Alsafwani
Keyword(s):  
Differential Equation ◽  
Steady State ◽  
Laser Heating ◽  
Dynamic Equilibrium ◽  
Element Model ◽  
Disk Surface ◽  
Flying Height ◽  
Lubricant Thickness ◽  
Flux Boundary Conditions ◽  
Disk Lubricant

Abstract The dynamic equilibrium among the condensation, evaporation and shear flow of the lubricant on a slider has been modeled by solving a continuum-based partial differential equation, with temperatures obtained from a finite element model. Zero-flux and specified-flux boundary conditions were used to study the trailing pad of a slider. The results show that the average lubricant thickness on the trailing pad gradually approaches a steady state, and the steady-state value increases with increasing disk lubricant thickness. A reduction of the flying height leads to a reduced steady-state slider lubricant thickness. The temperature rise of the disk surface tends to promote the lubricant transfer to the slider in a region close to the trailing edge. However, this effect may be locally suppressed by the laser-induced local thinning of the lubricant film on the disk.

Supersonic Virtual Valve Design for Numerical Simulation of a Large-Bore Natural Gas Engine

2007 ◽  
Vol 129 (4) ◽  
pp. 1065-1071 ◽  
Author(s):  
Gi-Heon Kim ◽  
Allan Kirkpatrick ◽  
Charles Mitchell
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Large Scale ◽  
Numerical Models ◽  
Three Dimensional ◽  
Injection System ◽  
Limiting Factor ◽  
Length Scales ◽  
Poppet Valve ◽  
The Impact

In many applications of supersonic injection devices, three-dimensional computation that can model a complex supersonic jet has become critical. However, in spite of its increasing necessity, it is computationally costly to capture the details of supersonic structures in intricate three-dimensional geometries with moving boundaries. In large-bore stationary natural gas fueled engine research, one of the most promising mixing enhancement technologies currently used for natural gas engines is high-pressure fuel injection. Consequently, this creates considerable interest in three-dimensional computational simulations that can examine the entire injection and mixing process in engines using high-pressure injection and can determine the impact of injector design on engine performance. However, the cost of three-dimensional engine simulations—including a moving piston and the kinetics of combustion and pollutant production—quickly becomes considerable in terms of simulation time requirements. One limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be three orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a methodology for the design of a simple geometry supersonic virtual valve that can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated. Downstream flow characteristics of the jets from an actual valve and various virtual valves are compared. Relevant mixing parameters, such as local equivalent ratio and turbulence kinetic energy, are evaluated in full-scale moving piston simulations that include the effect of the jet-piston interaction. A comparison of the results has indicated that it is possible to design a simple converging-diverging fuel nozzle that will produce the same jet and, subsequently, the same large-scale and turbulent-scale mixing patterns in the engine cylinder as a real poppet valve.

Effect of the Intermolecular Forces on the Flying Attitude of Sub-5 NM Flying Height Air Bearing Sliders in Hard Disk Drives

2002 ◽  
Vol 124 (3) ◽  
pp. 562-567 ◽  
Author(s):  
Lin Wu ◽  
D. B. Bogy
Keyword(s):  
Hard Disk Drives ◽  
Three Dimensional ◽  
Disk Surface ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Positive Pressure ◽  
Vertical Force ◽  
Air Bearing ◽  
Triangular Cell ◽  
Flying Attitude

When the spacing between the slider and the disk is smaller than 10 nm, the effect of the intermolecular forces between the two solid surfaces can no longer be ignored. This effect on the flying attitude of practical slider designs is investigated here numerically. The three-dimensional slider surface is discretized into non-overlapping unstructured triangles. The intermolecular forces between each triangular cell of the slider and the disk surface are formulated, and their contributions to the total vertical force, as well as the pitch and roll moments, are included in a previously developed steady state air bearing design code based on a multi-grid finite volume method with unstructured triangular grids [3–5]. It is found that the van der Waals force has significant influence on the flying height and has non-negligible effect on the pitch angle for both positive pressure sliders and negative pressure sliders, when the flying height is below 5 nm. When the flying height is below 0.5 nm, the repulsive portion of the intermolecular force becomes important and also has to be included.

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