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Physical And Chemical Characteristics Of Commercially Available Brake Shoe Lining Materials: A Comparative Study Nov 2004

Physical And Chemical Characteristics Of Commercially Available Brake Shoe Lining Materials: A Comparative Study

A.S. Md Abdul Haseeb

The physical and chemical characteristics of four commercial automotive brake shoe lining materials used in heavy vehicles have been investigated and compared. Relevant physical properties viz. density, water absorption and swelling characteristics were determined using standard test methods. X-ray diffraction, infrared spectroscopy and optical microscopic techniques were used to identify the constituents. It has been observed that all of the four friction materials contain phenol formaldehyde resin as the matrix. Other major ingredients were also the same in all the samples but their amount and size varied. These include asbestos as fibre reinforcement, barium sulphate as filler and brass particles ...


Physical And Chemical Characteristics Of Commercially Available Brake Shoe Lining Materials: A Comparative Study Nov 2004

Physical And Chemical Characteristics Of Commercially Available Brake Shoe Lining Materials: A Comparative Study

A.S. Md Abdul Haseeb

The physical and chemical characteristics of four commercial automotive brake shoe lining materials used in heavy vehicles have been investigated and compared. Relevant physical properties viz. density, water absorption and swelling characteristics were determined using standard test methods. X-ray diffraction, infrared spectroscopy and optical microscopic techniques were used to identify the constituents. It has been observed that all of the four friction materials contain phenol formaldehyde resin as the matrix. Other major ingredients were also the same in all the samples but their amount and size varied. These include asbestos as fibre reinforcement, barium sulphate as filler and brass particles ...


Strain-Induced Disorder And Phase Transformation In Hexagonal Boron Nitride Under Quasi-Homogeneous Pressure: In Situ X-Ray Study In A Rotational Diamond Anvil Cell, Valery I. Levitas, J. Hashemi, Y. Z. Ma Nov 2004

Strain-Induced Disorder And Phase Transformation In Hexagonal Boron Nitride Under Quasi-Homogeneous Pressure: In Situ X-Ray Study In A Rotational Diamond Anvil Cell, Valery I. Levitas, J. Hashemi, Y. Z. Ma

Valery I. Levitas

One of the challenges in characterization of strain-induced transformations is to create uniform pressure. In this letter, conditions for nearly homogeneous pressure distribution are predicted and achieved experimentally. Compared to hydrostatic loading, plastic shear generally reduces the transformation pressure significantly. We observed, however, an unexpected phenomenon: the transformation of hexagonal to superhard wurtzitic BN under pressure and shear initiated at a pressure comparable to that in hydrostatic compression ($\sim 10$ \ensuremath{{\rm ~GPa}}). In situ X-ray diffraction revealed that plastic shear increases the disorder, while hydrostatic compression does not. This increase neutralizes the transition pressure reduction caused by shear. For ...


Trapezoidal Phase-Shifting Method For 3d Shape Measurement, Peisen S. Huang, Song Zhang, Fu-Pen Chiang Oct 2004

Trapezoidal Phase-Shifting Method For 3d Shape Measurement, Peisen S. Huang, Song Zhang, Fu-Pen Chiang

Song Zhang

We propose a novel structured light method, namely trapezoidal phase-shifting method, for 3-D shape measurement. This method uses three patterns coded with phase-shifted, trapezoidal-shaped gray levels. The 3-D information of the object is extracted by direct calculation of an intensity ratio. Theoretical analysis showed that this new method was significantly less sensitive to the defocusing effect of the captured images when compared to the traditional intensity-ratio based methods. This important advantage makes large-depth 3-D shape measurement possible. If compared to the sinusoidal phase-shifting method, the resolution is similar, but the processing speed is at least 4.5 times faster. The ...


On The Equilibrium States Predicted By Second Moment Models In Rotating, Stably Stratified Homogeneous Shear Flow, Minsuk Ji, Paul A. Durbin Oct 2004

On The Equilibrium States Predicted By Second Moment Models In Rotating, Stably Stratified Homogeneous Shear Flow, Minsuk Ji, Paul A. Durbin

Paul A. Durbin

The structural equilibrium behavior of the general linear second-moment closure model in a stably stratified, spanwise rotating homogeneous shear flow is considered with the aid of bifurcation analysis. A closed form equilibrium solution for the anisotropy tensor aij, dispersion tensor Kij, dimensionless scalar variance q2/k (S/Sθ)2, and the ratio of mean to turbulent time scale ε/Sk is found. The variable of particular interest to bifurcation analysis, ε/Sk is shown as a function of the parameters characterizing the body forces: Ω/S (the ratio of the rotation rate to the mean shear rate) for rotation and ...


Asymptotic Accuracy Of Geoacoustic Inversions, Michele Zanolin, Ian Ingram, Aaron Thode, Nicholas C. Makris Sep 2004

Asymptotic Accuracy Of Geoacoustic Inversions, Michele Zanolin, Ian Ingram, Aaron Thode, Nicholas C. Makris

Michele Zanolin

Criteria necessary to accurately estimate a set of unknown geoacoustic parameters from remote acoustic measurements are developed in order to aid the design of geoacoustic experiments. The approach is to have estimation error fall within a specified design threshold by adjusting controllable quantities such as experimental sample size or signal-to-noise ratio (SNR). This is done by computing conditions on sample size and SNR necessary for any estimate to have a variance that (1) asymptotically attains the Cramer–Rao lower bound (CRLB) and (2) has a CRLB that falls within the specified design error threshold. Applications to narrow band deterministic signals ...


Microscale Simulation Of Martensitic Microstructure Evolution, Valery I. Levitas, Alexander V. Idesman, Dean L. Preston Sep 2004

Microscale Simulation Of Martensitic Microstructure Evolution, Valery I. Levitas, Alexander V. Idesman, Dean L. Preston

Valery I. Levitas

A new model for the evolution of multivariant martensitic microstructure in single crystals and polycrystals is developed. In contrast with Landau-Ginzburg models, which are limited in practice to nanoscale specimens, this new scale-free model is valid for length scales greater than 100 nm and without an upper bound. It is based on a thermodynamic potential in the volume fractions of the martensitic variants that exhibits an instability resulting in microstructure formation. Simulated microstructures in elastic single crystals and polycrystals under uniaxial loading are in qualitative agreement with those observed experimentally.


Contribution Of Support Means To Stresses Developed In Sheet Metal Coils, Jonathan A. Wickert, Y.M. Lee Aug 2004

Contribution Of Support Means To Stresses Developed In Sheet Metal Coils, Jonathan A. Wickert, Y.M. Lee

Jonathan A. Wickert

Sheet metal is often stored in large wound coils and processed through such manufacturing stages as cleaning, coating, and slitting in a finishing plant or thickness reduction in a rolling mill. During winding and unwinding operations, as well as during storage and transportation, a coil can be supported in a variety of methods. The coil can be formed on a relatively compliant fiber core, or it can be mounted with the core onto a drive shaft or a pair of core chucks. The stresses within the coil develop in response to the sheet metal's material properties, the process tension ...


Dual-Pump Dual-Broadband Coherent Anti-Stokes Raman Scattering In Reacting Flows, Sukesh Roy, Terrence R. Meyer, Robert P. Lucht, Mikael Afzelius, Per-Erik Bengtsson, James R. Gord Jul 2004

Dual-Pump Dual-Broadband Coherent Anti-Stokes Raman Scattering In Reacting Flows, Sukesh Roy, Terrence R. Meyer, Robert P. Lucht, Mikael Afzelius, Per-Erik Bengtsson, James R. Gord

Terrence R Meyer

A dual-pump, dual-broadband coherent anti-Stokes Raman scattering system for simultaneous measurements of temperature and concentrations of N2, O2, and CO2 in reacting f lows is demonstrated. In this system pure rotational transitions of N2 O2 and rovibrational transitions of N2 CO2 are probed simultaneously with two narrowband pump beams, a broadband pump beam, and a broadband Stokes beam. The main advantage of this technique is that it permits accurate temperature measurements at both low and high temperatures as well as concentration measurements of three molecules.


Velocity Effects On The Wear, Friction And Tribochemistry Of Aluminum Mmc Sliding Against Phenolic Brake Pad Jun 2004

Velocity Effects On The Wear, Friction And Tribochemistry Of Aluminum Mmc Sliding Against Phenolic Brake Pad

A.S. Md Abdul Haseeb

Two aluminum metal matrix composites (MMC) reinforced with 13 vol.% of SiC or B4C particles were made by stir casting followed by hot extrusion. Effects of sliding velocity on the wear, friction and tribochemistry of the worn surfaces of both composites sliding against a commercial phenolic brake pad have been investigated under dry condition. The wear tests were carried out using a pin-on-disc type apparatus at two linear sliding speeds: 1.62 and 4.17 m s-1 under a constant contact pressure of 0.75 MPa for a sliding distance of 5832 m. The coefficient of friction was recorded and ...


Solid-Solid Phase Transformation Via Virtual Melting Significantly Below The Melting Temperature, Valery I. Levitas, Bryan F. Henson, Laura B. Smilowitz, Blaine W. Asay Jun 2004

Solid-Solid Phase Transformation Via Virtual Melting Significantly Below The Melting Temperature, Valery I. Levitas, Bryan F. Henson, Laura B. Smilowitz, Blaine W. Asay

Valery I. Levitas

A new phenomenon is theoretically predicted, namely, that solid-solid transformation with a relatively large transformation strain can occur through virtual melting along the interface at temperatures significantly (more than 100 K) below the melting temperature. The energy of elastic stresses, induced by transformation strain, increases the driving force for melting and reduces the melting temperature. Immediately after melting, the stresses relax and the unstable melt solidifies. Fast solidification in a thin layer leads to nanoscale cracking, which does not affect the thermodynamics and kinetics of solid-solid transformation. Seven theoretical predictions are in quantitative agreement with experiments conducted on the β ...


A Microscale Model For Strain-Induced Phase Transformations And Chemical Reactions Under High Pressure, Valery I. Levitas Jun 2004

A Microscale Model For Strain-Induced Phase Transformations And Chemical Reactions Under High Pressure, Valery I. Levitas

Valery I. Levitas

A simple strain-controlled kinetic equation for strain-induced phase transformations and chemical reactions is thermodynamically derived. This model is applied to explain various mechanochemical phenomena observed under compression and shear of materials in diamond or Bridgman anvils. In particular, it explains zero-pressure hysteresis and the appearance of new phases, especially strong phases, which were not obtained without shear. Also an explanation was obtained as to why a nonreacting matrix with a yield stress higher (lower) than that for reagents significantly accelerates (slows down) the reactions. Some methods to characterize and control strain-induced transformations and reactions are suggested.


Velocity Effects On The Wear, Friction And Tribochemistry Of Aluminum Mmc Sliding Against Phenolic Brake Pad May 2004

Velocity Effects On The Wear, Friction And Tribochemistry Of Aluminum Mmc Sliding Against Phenolic Brake Pad

A.S. Md Abdul Haseeb

Two aluminum metal matrix composites (MMC) reinforced with 13 vol.% of SiC or B4C particles were made by stir casting followed by hot extrusion. Effects of sliding velocity on the wear, friction and tribochemistry of the worn surfaces of both composites sliding against a commercial phenolic brake pad have been investigated under dry condition. The wear tests were carried out using a pin-on-disc type apparatus at two linear sliding speeds: 1.62 and 4.17 m s-1 under a constant contact pressure of 0.75 MPa for a sliding distance of 5832 m. The coefficient of friction was recorded and ...


Food Based Approaches For A Healthy Nutrition In Africa, Mamoudou Hama Dicko May 2004

Food Based Approaches For A Healthy Nutrition In Africa, Mamoudou Hama Dicko

Pr. Mamoudou H. DICKO, PhD

The latest estimates of the FAO demonstrate the problems of the fight against hunger. These problems are manifested by the ever-increasing number of chronically undernourished people worldwide. Their numbers during the 1999-2001 period were estimated at about 840 million of which 798 million live in developing countries. Sub-Saharan Africa alone represented 198 million of those. In this part of Africa the prevalence of undernourishment ranges from 5-34%, causing growth retardation and insufficient weight gain among one third of the children under five years of age and resulting in a mortality of 5-15% among these children. Malnutrition resulting from undernourishment is ...


مقاومت مصالح گیر ویرایش ششم زبان اصلی, Gere Jan 2004

مقاومت مصالح گیر ویرایش ششم زبان اصلی, Gere

mehdi raghebi

No abstract provided.


High-Pressure Mechanochemistry: Conceptual Multiscale Theory And Interpretation Of Experiments, Valery I. Levitas Jan 2004

High-Pressure Mechanochemistry: Conceptual Multiscale Theory And Interpretation Of Experiments, Valery I. Levitas

Valery I. Levitas

Fifteen mechanochemical phenomena observed under compression and plastic shear of materials in a rotational diamond anvil cell (RDAC) are systematized. They are related to strain-induced structural changes (SCs) under high pressure, including phase transformations (PTs) and chemical reactions. A simple, three-scale continuum thermodynamic theory and closed-form solutions are developed which explain these phenomena. At the nanoscale, a model for strain-induced nucleation at the tip of a dislocation pile-up is suggested and studied. At the microscale, a simple strain-controlled kinetic equation for the strain-induced SCs is thermodynamically derived. A macroscale model for plastic flow and strain-induced SCs in RDAC is developed ...


Three-Dimensional Simulations Of Self-Assembly Of Hut Shaped Si-Ge Quantum Dots, Ashwin Ramasubramaniam, V. B. Shenoy Dec 2003

Three-Dimensional Simulations Of Self-Assembly Of Hut Shaped Si-Ge Quantum Dots, Ashwin Ramasubramaniam, V. B. Shenoy

Ashwin Ramasubramaniam

This article presents the results of three-dimensional modeling of heteroepitaxial thin film growth with the objective of understanding recent experiments on the early stages of quantum dot formation in SiGe/Si systems. We use a continuum model, based on the underlying physics of crystallographic surface steps, to study the growth of quantum dots, their spatial ordering and coarsening behavior. Using appropriate parameters, obtained from atomistic calculations, the (100) orientation is found to be unstable under compressive strains. The surface energy now develops a minimum at an orientation that may be interpreted as the (105) facet observed in SiGe/Si systems ...