Evaluation of Variable-Temperature Cures

1928 ◽  
Vol 1 (3) ◽  
pp. 423-440
Author(s):  
J. R. Sheppard ◽  
W. B. Wiegand
Keyword(s):  
Temperature Gradient ◽  
Initial Temperature ◽  
Variable Temperature ◽  
Practical Importance ◽  
Direct Reading ◽  
Time Curve ◽  
Constant Temperature Gradient ◽  
Several Variables ◽  
Exact Evaluation ◽  
Effect Time

Abstract Employing the generally accepted empirical rule that intensity of curing action doubles with a rise of 15° F., relations are developed between the several variables of a cure segment with a constant temperature gradient—viz., “intensity of curing action,” “curing effect,” time, and temperature—and the constants of such a cure, initial temperature and temperature gradient. Exact evaluation of cures is extended to schedules involving variable temperatures by the equations showing curing effect as a function of the other properties of a cure. These are the equations of chief practical importance. Curing effect, the measure of the net value of a schedule in effecting vulcanization, may be determined for a given schedule either by calculation from one of the “effect” equations, by direct reading from one of the several herein displayed graphs of effect vs. other properties, or by estimation of the area under an intensity-time curve.

Phase changes and convection in the Earth’s mantle

1965 ◽  
Vol 258 (1088) ◽  
pp. 276-283 ◽  
Keyword(s):  
Temperature Gradient ◽  
Phase Change ◽  
Initial Temperature ◽  
Phase Changes ◽  
Homogeneous Layer ◽  
Transformation Zone ◽  
Earth’S Mantle ◽  
Transition Level ◽  
Transformation Rates

A phase change may hinder or enhance convection, depending on its characteristics. Univariant transformations such as may occur in the mantle constitute a barrier to convection unless the motion starts at some distance above or below the transition level; an initial temperature gradient in excess of the adiabatic value is also required. Multivariant transformations only require, in the transformation zone, an initial gradient slightly greater than the adiabatic value for a homogeneous layer. The effect on convection of transformation rates is not likely to be serious.

Analytical Solutions and Derivation of Relative Permeabilities for Water-Heavy Oil Displacement and Gas-Heavy Oil Gravity Drainage Under Non-Isothermal Conditions

2016 ◽  
Vol 19 (01) ◽  
pp. 181-191 ◽  
Author(s):  
F. J. Argüelles-Vivas ◽  
T.. Babadagli
Keyword(s):  
Temperature Gradient ◽  
Relative Permeability ◽  
Heavy Oil ◽  
Variable Temperature ◽  
Spontaneous Imbibition ◽  
Analytical Models ◽  
Gravity Drainage ◽  
Positive Temperature ◽  
Relative Permeability Curves ◽  
Isothermal Gas

Summary Analytical models were developed for non-isothermal gas/heavy-oil gravity drainage and water-heavy oil displacements in round capillary tubes including the effects of a temperature gradient throughout the system. By use of the model solution for a bundle of capillaries, relative permeability curves were generated at different temperature conditions. The results showed that water/gas-heavy oil interface location, oil-drainage velocity, and production rate depend on the change of oil properties with temperature. The displacement of heavy oil by water or gas was accelerated under a positive temperature gradient, including the spontaneous imbibition of water. Relative permeability curves were greatly affected by temperature gradient and showed significant changes compared with the curves at constant temperature. Clarifications were made as to the effect of variable temperature compared with the constant (but high) temperatures throughout the bundle of capillaries.

Thermal-Mechanical Study of 3D Printing Technology for Rail Repair

2018 ◽  
Author(s):  
Ershad Mortazavian ◽  
Zhiyong Wang ◽  
Hualiang Teng
Keyword(s):  
Thermal Analysis ◽  
Thermal Expansion ◽  
3D Printing ◽  
Stress Distribution ◽  
Temperature Gradient ◽  
Initial Temperature ◽  
Mechanical Analysis ◽  
Von Mises Stress ◽  
Additive Materials ◽  
Von Mises

The complicated steel wheel and rail interaction on curve causes side wear on rail head. Thus, the cost of maintenance for the track on curve is significantly higher than that for track on a tangent. The objective of this research is to develop 3D printing technology for repairing the side wear. In this paper, the study examines induced residual thermal stresses on a rail during the cooling down process after 3D printing procedure using the coupled finite volume and finite element method for thermal and mechanical analysis respectively. The interface of the railhead and additive materials should conserve high stresses to prevent any crack initiation. Otherwise, the additive layer would likely shear off the rail due to crack propagation at the rail/additive interface. In the numerical analysis, a cut of 75-lb ASCE (American Society of Civil Engineers) worn rail is used as a specimen, for which a three-dimensional model is developed. The applied residual stresses, as a result of temperature gradient and thermal expansion coefficient mismatch between additive and rail materials, are investigated. At the beginning, the worn rail is at room temperature while the additive part is at a high initial temperature. Then, additive materials start to flow thermal energy into the worn rail and the ambient. The thermal distribution results from thermal analysis are then employed as thermal loads in the mechanical analysis to determine the von-Mises stress distribution as the decisive component. Then, the effect of preheating on residual stress distribution is studied. In this way, the thermo-mechanical analysis is repeated with an increase in railhead’s initial temperature. In thermal analysis, the temperature contours at different time steps for both the non-preheated and preheated cases indicate that preheating presents remarkably lower temperature gradient between rail and additive part and also represents a more gradual cooling down process to allow enough time for thermal expansion mismatch alignment. In mechanical analysis, the transversal von-Mises stress distribution at rail/additive interface is developed for all cases for comparison purposes. It is shown that preheating is a key factor to significantly reduce residual stresses by about 40% at all points along transversal direction of interface.

Fractionation of polyolefins in a column with a variable temperature gradient

1972 ◽  
Vol 14 (3) ◽  
pp. 808-812 ◽  
Author(s):  
A.A. Buniyat-Zade ◽  
Ye.A. Osipov ◽  
A.B. Azimova
Keyword(s):  
Temperature Gradient ◽  
Variable Temperature

Solid-State Carbon-13 NMR Studies of Vulcanized Elastomers. VI. Relaxation in Sulfur-Vulcanized Natural Rubber

1989 ◽  
Vol 62 (1) ◽  
pp. 82-97 ◽  
Author(s):  
Mladen Andreis ◽  
Juwhan Liu ◽  
Jack L. Koenig
Keyword(s):  
Experimental Data ◽  
Solid State ◽  
Variable Temperature ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Techniques ◽  
Nmr Studies ◽  
Time Curve ◽  
Correlation Times ◽  
Spin Lattice

Abstract Molecular motions in sulfur-vulcanized NR are investigated by solid state 13C NMR relaxation techniques. Since the high-resolution spectra of crosslinked samples exhibit overlapping in the aliphatic region, a combined application of variable temperature spin-lattice relaxation measurements and the computer simulation of the overlapped spectral region is used in order to detect resonance signals. Motional restrictions introduced by crosslinks are investigated from the temperature dependence of nT1 relaxation times for individual carbons. The V-curves for all polyisoprene signals and for the detectable signals arising from the network units exhibit a similar general trend with increased curing time: curve broadening, shift of the minima to higher temperatures, and increase of the T1 min values. All the backbone carbons show quantitatively similar effects of vulcanization on the spin-lattice relaxation. At shorter curing times, motional restrictions for the methyl side group are more pronounced compared to the main-chain carbons. The experimental data suggest that the isotropic motion is strongly affected by the crosslinking. Librational motion is less affected, while the change in rotational motion has no significant influence on the relaxation curve. Although experimental data cover a relatively narrow temperature range, not sufficiently wide for a more accurate quantitative analysis, the results indicate that concepts of plural correlation times and a distribution of correlation times are applicable.

Vortex dynamics during N–S and S–N transitions of Y–Ba–Cu–O superconductors under the effect of temperature gradient and thermal cycling

1997 ◽  
Vol 12 (11) ◽  
pp. 3090-3098 ◽  
Author(s):  
I. Kirschner ◽  
A. C. Bódi ◽  
R. Laiho ◽  
L. Lähderanta
Keyword(s):  
Temperature Gradient ◽  
Physical Environment ◽  
Variable Temperature ◽  
Ac Susceptibility ◽  
Vortex Motion ◽  
Effect Of Temperature ◽  
One Dimensional ◽  
Nonequilibrium Temperature ◽  
The One ◽  
Flux Expulsion

AC susceptibility of ac has been measured simultaneously in three different ranges of Y–Ba–Cu –O ceramic samples in the presence of a large and variable temperature gradient. The results obtained for normal-superconducting or superconducting-normal transitions under the effect of the one-dimensional nonequilibrium temperature distribution reveal the vortex motion to consist of not only conventional flux expulsion (or flux penetration), but flux exchange too, appearing between different ranges of samples and between samples and their close physical environment. The thermal cycles are shown to represent a supplementary heat treatment, increasing the homogeneity of the sample and decreasing the pinning, which accelerate the process of vortex motion.

A New Model System for the Study of Complex Dynamical Enzyme Reactions. II. Oscillations in a Reaction-Diffusion-Convection System

1988 ◽  
Vol 43 (11) ◽  
pp. 995-1001
Author(s):  
Gerold Baier ◽  
Peter Urban ◽  
Klaus Wegmann
Keyword(s):  
Temperature Gradient ◽  
Complete System ◽  
Convective Motion ◽  
Enzyme Reaction ◽  
Reaction Diffusion ◽  
Model System ◽  
Chemical Gradient ◽  
Constant Temperature Gradient ◽  
Enzyme Reactions ◽  
Diffusion Convection

Abstract A nonlinear enzyme reaction in a chemical gradient with an artificial feed-back loop is modified by the application of a constant temperature gradient leading to laminar convective motion of the fluid at an electrode. The complete system is shown to undergo a bifurcation into a limit cycle as a function of the applied temperature gradient. The effect of other parameters on the oscillation is described. More complicated types of behavior are expected in parameter space.

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