Magnetic Head-Media Interface Temperatures: Part 2—Application to Magnetic Tapes

1987 ◽  
Vol 109 (2) ◽  
pp. 252-256 ◽  
Author(s):  
B. Bhushan
Keyword(s):  
Analytical Model ◽  
Magnetic Particles ◽  
Temperature Drop ◽  
Interface Temperature ◽  
Thermal Gradients ◽  
Asperity Contact ◽  
Sliding Surface ◽  
Magnetic Head ◽  
Head Surface ◽  
Radiometric Technique

An analytical model has been used to predict the interface temperature of a typical magnetic head-tape contact and of isolated (exposed) magnetic particles in contact with the head. Average and maximum interface temperatures for the assumed head-tape interface are about 7° and 10° C, respectively. If the exposed magnetic particles contact the head surface, the average and maximum temperture rises could be about 600° and 900° C, respectively. The duration of an asperity contact is about 2 to 4 μs and the thermal gradients perpendicular to the sliding surface are very large (a temperature drop of 90 percent in a depth of less than the radius of an asperity contact or a few micrometers). The predicted temperatures are compared with the temperatures previously measured using an infrared radiometric technique.

Magnetic Head-Media Interface Temperatures—Part 3: Application to Rigid Disks

1992 ◽  
Vol 114 (3) ◽  
pp. 420-430 ◽  
Author(s):  
B. Bhushan
Keyword(s):  
Thin Film ◽  
Contact Area ◽  
Magnetic Particles ◽  
Temperature Drop ◽  
Transient Temperature ◽  
Thermal Gradients ◽  
Asperity Contact ◽  
Disk Interface ◽  
Zn Ferrite ◽  
Rigid Disks

A thermal analysis has been used to predict transient temperature rises at a typical head-particulate-disk interface and a head-thin-film-disk interface. Thermal properties of the various thin-films used in the construction of magnetic rigid disks are measured. Average and maximum transient temperature rises for the assumed head-particulate-disk interface over the contact area are 34 and 44°C, respectively for an Al2O3-TiC slider. If the exposed magnetic particles or alumina particles contact the slider surface, the transient temperature rise could be more than 1000°C. Average and maximum transient temperature rises for the assumed head-thin-film-disk interface over the contact area are 56 and 81°C, respectively for an Al2O3-TiC slider and 77 and 110°C, respectively for an Mn-Zn ferrite slider. The durations of asperity contact generally are less than 100 ns. The thermal gradients perpendicular to the sliding surfaces are very large (a temperature drop of 90 percent in a depth of typically less than a contact diameter or less than a micron).

Sliding Surface Interface Temperatures

1973 ◽  
Vol 95 (1) ◽  
pp. 59-64 ◽  
Author(s):  
N. H. Cook ◽  
B. Bhushan
Keyword(s):  
Surface Topography ◽  
Temperature Rise ◽  
Surface Hardness ◽  
Thermal Parameters ◽  
Interface Temperature ◽  
Sliding Surface ◽  
Effective Surface ◽  
Basic Model

An analysis is proposed for estimating the average interface temperature rise during sliding of two surfaces. The basic model includes surface topography statistics, frictional conditions, the effective surface hardness, and thermal parameters. In 75 percent of the material pairs studied, the analysis gives fairly good results. It appears applicable to either dry or lubricated surfaces.

Deriving an Analytical Model for Hydro-Magnetic Micro Flow Controller

2008 ◽  
Author(s):  
Mahdi Esmaily Moghadam ◽  
Mohammad Behshad Shafii
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Magnetic Particles ◽  
Switching Time ◽  
Critical Factor ◽  
Pressure Head ◽  
Experimental Results ◽  
Working Fluid ◽  
Effective Parameters ◽  
Flow Controller

Fluid control, namely pumping and valving, is a critical factor in the performance of micro-fluidic systems. In recent years a variety of micro-fluidic systems are developed for the purpose of miniaturizing fluid handling, and chemical analysis to develop Lab On a Chip (LOC) technology. The mentioned facts resulted in design and fabrication of a novel hydro-magnetic flow controller. The idea behind this device is that magnetic particles, mixed and dispersed in a carrier liquid, can be accumulated in the form of a piston. Depending upon dragging speed of these pistons, which itself is a function of switching time, this device can be used to either increase (pumping) or decrease (valving) the flow rate. The valving characteristic of the setup, which occurs at higher switching times, was concurrent with regular forming of pistons in micro-tube. Experimental results in this part show a meaningful trend for the flow rate changes versus effective parameters of the flow. Considering this fact, lead us to propose a mathematical (analytical) model, which is a function of concerning parameters. Pressure head difference, concentration, material of particles, switching time, working fluid and, switching mode, depending on their complexity, have been introduced into the mathematical model, completely theoretically or semi-experimentally. The equations were derived based on the recognition of the leakage flow through the formed pistons and the pumped flow after each switching. The model was validated by the experimental results for nickel particles of less than 10μ in diameter and 0.5 gNi/100ccH2O concentration in water for a defined pressure head in a pressure driven flow setup.

Analytical model of microfluidic transport of non-magnetic particles in ferrofluids under the influence of a permanent magnet

2011 ◽  
Vol 10 (6) ◽  
pp. 1233-1245 ◽  
Author(s):  
Taotao Zhu ◽  
Darcy J. Lichlyter ◽  
Mark A. Haidekker ◽  
Leidong Mao
Keyword(s):  
Permanent Magnet ◽  
Analytical Model ◽  
Magnetic Particles

Silicon Temperature and Thermal Gradients Measurements in a Rapid Thermal Processor Operating at Atmospheric Pressure or in Vacuum

1987 ◽  
Vol 92 ◽  
Author(s):  
J-M. Dilhac ◽  
C. Ganibal ◽  
A. Martinez
Keyword(s):  
Thermal Radiation ◽  
Experimental Evidence ◽  
Thermal History ◽  
Atmospheric Pressure ◽  
Temperature Drop ◽  
Gas Pressure ◽  
Optical Pyrometer ◽  
Thermal Gradients ◽  
Time Profiles ◽  
Temperature Time

ABSTRACTTemperature-time profiles obtained by an optical pyrometer and a mechanically contacted thermocouple are first presented it appears that the thermocouple response is sensitive to the pressure in the processing chamber. The authors suggest that, in vacuum, the thermocouple is thermally isolated from the wafer, until the temperature is high enough for thermal radiation exchanges to occur. Experimental evidence of the influence of thermal history, and of gas pressure and flow, on temperature drop at periphery of the wafer is then given.

Interphase matter transfer: an experimental study of condensation of mercury

1981 ◽  
Vol 378 (1774) ◽  
pp. 305-327 ◽  
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Vapour Pressure ◽  
Temperature Drop ◽  
Vertical Plane ◽  
Film Condensation ◽  
Interface Temperature ◽  
Condensation Coefficient ◽  
Condensation Rate ◽  
Matter Transfer

Comparisons between interphase matter-transfer theory and measurements have, in the past, been hindered by uncertainties about the ‘condensation coefficient’. Large experimental errors have often been misinterpreted as indicating low values of the condensation coefficient. Condensation experiments with metals are convenient for the study of interphase matter transfer since, owing to the high thermal conductivity of the liquid, the temperature drop across the condensate film is small and, particularly at low pressures and high condensation rates, the temperature discontinuity at the vapour-liquid interface is of measurable magnitude. Condensation rate, and vapour and condenser surface temperature measurements have been made during film condensation of mercury on a vertical, plane, square (side 40 mm), nickel-plated, copper surface. Thermocouples, accurately located and spaced through the copper condenser block, served to measure, by extrapolation, the temperature of the copper-nickel interface and, from the temperature gradient, the heat flux from which the condensation mass flux was determined. Special care was taken to ensure that the results were not vitiated by the presence in the vapour of noncondensing gases. The observations cover wider ranges of vapour pressure (temperature) and condensation rate (heat flux) than hitherto studied, i.e. 50-4300 Pa (378-493 K) and 0.2- 3.6 kgm ~2 s- 1 (56-1062 kW m -2 ) respectively. The results are considered to have enhanced accuracy. In particular, after the accuracy of calibration and positioning of the thermocouples, and th at of the thermoelectric measurements has been considered, it is estimated that the condenser surface temperature was measured to within around ± 0.1 K. Interface temperature discontinuities up to around 70 K have been observed at low vapour pressure and high condensation rate. The results lend support to recent theoretical studies and indicate that the condensation coefficient exceeds 0.9.

Extrapolation Errors in Thermal Contact Resistance Measurements

1975 ◽  
Vol 97 (2) ◽  
pp. 305-307 ◽  
Author(s):  
T. R. Thomas
Keyword(s):  
Temperature Gradient ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Temperature Drop ◽  
Interface Temperature ◽  
Better Than

In the classic split-bar determination of thermal contact resistance the temperature drop across the interface is estimated by extrapolating a temperature gradient measured remotely. It is shown that this can give rise to substantial errors which cannot greatly be reduced by increasing the number of measurements. It is suggested that due to extrapolation errors few interface temperature drops have ever been determined to better than 1/2 °K, and that this may account for some of the discrepancies between published contact resistances, particularly those measured at high loads.

scholarly journals Modeling and design of tuned mass dampers using sliding variable friction pendulum bearings

2020 ◽  
Vol 231 (12) ◽  
pp. 5021-5046
Author(s):  
Emiliano Matta ◽  
Rita Greco
Keyword(s):  
Friction Coefficient ◽  
Pressure Distribution ◽  
Analytical Model ◽  
Seismic Isolation ◽  
Outer Region ◽  
Design Parameters ◽  
Sliding Surface ◽  
Restoring Force ◽  
Variable Friction ◽  
Friction Pendulum

Abstract An effective vibration control device, the pendulum tuned mass damper (P-TMD), can be easily realized as a mass supported on rolling or sliding pendulum bearings. While the bearings’ concavity provides the desired gravitational restoring force, the necessary dissipative force can be obtained either from additional dampers installed in parallel with the bearings or from the same friction resistance developing within each bearing between the roller/slider and the rolling/sliding surface. The latter solution may prove cheaper and more compact but implies that the P-TMD effectiveness will be amplitude dependent if the friction coefficient is kept uniform along the rolling/sliding surface, as in conventional friction bearings. In this case, the friction P-TMD will be as efficient as a viscous P-TMD only at a given vibration level, with large performance reductions at other levels. To avoid this inconvenience, this paper proposes a new type of sliding variable friction pendulum (VFP) TMD, called the VFP-TMD, in which the sliding surface is divided into two concentric regions: a circular inner region, having the lowest possible friction coefficient and the same dimensions of the slider, and an annular outer region, having a friction coefficient set to an optimal value. A similar arrangement has been recently proposed to realize adaptive seismic isolation devices, but no specific application to TMDs is reported. To assess the VFP-TMD performance, first its analytical model is derived, rigorously accounting for geometric nonlinearities as well as for the variable (in time and space) pressure distribution along the contact area, and then, an optimal design methodology is presented. Finally, numerical simulations show the influence of the main design parameters on the device behavior and demonstrate that the VFP-TMD can achieve nearly the same effectiveness of viscous P-TMDs, while considerably outperforming conventional uniform-friction P-TMDs. The proposed analytical model can be used to enhance or validate existing models of VFP isolators that assume a constant and uniform contact pressure distribution.

Study on the cyclotriphosphazene film on magnetic head surface

2004 ◽  
Vol 37 (7) ◽  
pp. 585-590 ◽  
Author(s):  
Luo Jianbin ◽  
Yang Mingchu ◽  
Zhang Chaohui ◽  
Pan Guoshun ◽  
Wen Shizhu
Keyword(s):  
Magnetic Head ◽  
Head Surface

Magnetic Head-Media Interface Temperatures: Part 1—Analysis

1987 ◽  
Vol 109 (2) ◽  
pp. 243-251 ◽  
Author(s):  
B. Bhushan
Keyword(s):  
The Other ◽  
Temperature History ◽  
Asperity Contact ◽  
Thermal Interaction ◽  
Flash Temperature ◽  
Magnetic Head ◽  
Temperature Variations ◽  
Sliding Surfaces ◽  
Basic Model ◽  
Asperity Contacts

A “generalized” thermal analysis is described to estimate the flash temperature during sliding when both surfaces are of more or less equal roughness or one surface is substantially smoother than the other. High- and low-speed cases are considered. The basic model includes surface-topography statistics, frictional conditions, and mechanical and thermal parameters. Temperature history during the life of an individual asperity contact is calculated, from which average temperatures of an asperity contact are calculated. Thermal interaction of neighboring asperity contacts is considered. Then, an analysis is presented to show how individual asperity temperatures should be averaged. Temperature variations perpendicular to the sliding surfaces are also analyzed. Throughout the analysis, closed-form equations are developed, which can be conveniently used in the design of any sliding interface.

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