A Study of Stiffness Testing of Elastomers at Low Temperatures

1955 ◽  
Vol 28 (1) ◽  
pp. 335-347
Author(s):  
F. S. Conant
Keyword(s):  
Low Temperature ◽  
Temperature Region ◽  
Low Temperatures ◽  
Temperature Limit ◽  
Test Methods ◽  
Beam Method ◽  
Stiff Material ◽  
Rubberlike Materials ◽  
Good Agreement

Abstract In light of the above discussion, it does not appear logical to choose a “best” test for determining low-temperature moduli. A study of the data as a whole indicates that the correlation between the two sets of values from the simple beam-method (laboratories C-1 and C-2) are closest, but there is nothing to show that they are the most valid. It should be emphasized that, in the temperature region of greatest technical importance, that is, where the rubber is changing from its ordinary flexible state to a hard stiff material, the different tests show good agreement. A low-temperature limit of serviceability would be close to −80° F for the Hevea gum and −60° F for the GR-S by each of the methods studied. Another conclusion that might well be reached by a study of the test methods and data presented is that the term “modulus”, as applied to rubberlike materials, is rather vague unless the method of obtaining that modulus is also given.

Fractography and Fracture Toughness Measurement

2009 ◽  
Vol 409 ◽  
pp. 17-27 ◽  
Author(s):  
Roger Morrell
Keyword(s):  
Fracture Toughness ◽  
Surface Crack ◽  
Ceramic Materials ◽  
Test Methods ◽  
Fracture Toughness Test ◽  
Single Edge ◽  
Fracture Toughness Measurement ◽  
Beam Method ◽  
Toughness Measurement ◽  
Good Agreement

Using a variety of advanced ceramic materials, a comparison has been conducted of fracture toughness test methods using the single edge vee-notch beam method and the surface crack in flexure method, the latter restricted to optical fractography. Good agreement has been found between the two methods on materials which were amenable to the SCF method. It has further been shown that the SEVNB method can produce reliable results on materials to which the SCF method is not readily applicable.

ESR Linewidths of Vanadyl β-Diketonate Complexes in Liquid Solutions

1975 ◽  
Vol 53 (15) ◽  
pp. 1492-1498
Author(s):  
T. E. Eagles ◽  
R. E. D. McClung
Keyword(s):  
Electron Spin Resonance ◽  
Low Temperature ◽  
Temperature Region ◽  
Low Temperatures ◽  
Esr Spectra ◽  
Simple Description ◽  
Solvent Viscosity ◽  
Spin Resonance ◽  
Liquid Solutions ◽  
Rotational Interaction

The electron spin resonance (ESR) spectra of a series of vanadyl β-diketonate complexes in dilute solutions in several inert solvents have been investigated. The widths of the lines in these spectra have been interpreted in terms of the Kivelson linewidth theory. Significant discrepancies between the experimental linewidths and those predicted by the theory were found at low temperatures and high solvent viscosities. It is concluded that the Stokes–Einstein relationship, which relates the reorientational correlation time to the solvent viscosity, is not valid in the low temperature region and that the simple description of spin relaxation by the spin–rotational interaction given by Atkins and Kivelson is inadequate.

scholarly journals Эффект модификации вклада термоэмиссии локализованных зарядов в релаксацию фотоотклика монокристалла TlGaSe-=SUB=-2-=/SUB=-

2020 ◽  
Vol 62 (4) ◽  
pp. 596
Author(s):  
А.П. Одринский
Keyword(s):  
Low Temperature ◽  
Temperature Region ◽  
Ferroelectric State ◽  
Charge Localization ◽  
Good Agreement

The studing of thermoemission process peculiarities from the of charge localization centers in electrically non-uniform TlGaSe2 crystal are presented. Heterogeneity was formed by preliminary polarization of a sample at low temperature of ferroelectric state of the crystal. The results are good agreement with peculiarities of the localized charges thermoemission registration on TlInS2 in the temperature region of ferroelectric state of the crystal.

SPIN FLUCTUATIONS IN TCo2 STUDIED BY RESISTIVITY AND THERMOPOWER EXPERIMENTS (T = Y, Lu, Sc, Hf, Zr, Ce)

1993 ◽  
Vol 07 (01n03) ◽  
pp. 370-373 ◽  
Author(s):  
N. BARANOV ◽  
E. BAUER ◽  
E. GRATZ ◽  
R. HAUSER ◽  
A. MARKOSYAN ◽  
...  
Keyword(s):  
Low Temperature ◽  
Specific Heat ◽  
Temperature Dependence ◽  
Temperature Region ◽  
Low Temperatures ◽  
Spin Fluctuations ◽  
General Tendency ◽  
Electronic Specific Heat ◽  
Temperature Dependent

The temperature dependence of the resistivity and the thermopower in the region from 4.2K up to 1000K for the six isostructural paramagnetic compounds TCo 2 (T=Y, Lu, Sc, Hf, Zr, Ce) is studied. The resistivity ρ (T) follows a T 2 dependence at low temperatures in all these compounds. Plotting the A values into an A vs. γ2 diagram shows that YCo 2, LuCo 2, and ScCo 2 are spinfluctuation systems (A and γ denote the coefficients in ρ (T) = ρ0 + AT 2 and that of the electronic specific heat, respectively) HfCo 2 and ZrCo 2 do not fit into this general tendency in the ( A , γ2)-diagram. The temperature dependent thermopower S(T) in YCo 2, LuCo 2 and ScCo 2 exhibits a pronounced minimum in the low temperature region. These minima are obviously connected with the existence of spin fluctuations (paramagnon-drag). Spin fluctuations in HfCo 2 and ZrCo 2 are less important. This we conclude also from the ten times smaller A-values and the missing minimum in the thermopower at low temperatures.

Heat Conductivity of Rubber at Low Temperatures

1940 ◽  
Vol 13 (4) ◽  
pp. 830-830
Author(s):  
Adolf Schallamach
Keyword(s):  
Low Temperature ◽  
Physical Properties ◽  
Temperature Region ◽  
Heat Conductivity ◽  
Low Temperatures ◽  
Room Temperature ◽  
Tire Rubber ◽  
Order Of Magnitude ◽  
Temperature Work

Abstract While examining the possibilities of applying rubber in low temperature work, we were hampered by the lack of available data on its physical properties at low temperatures. We were aware of the difficulties to be expected in making accurate measurements in that temperature region, and this applied especially to the heat conductivity, in which we were particularly interested. To obtain at least an estimate of the order of magnitude, we carried out some measurements of the heat conductivity of commercial rubber (North British tire rubber) at room temperature and at the temperature of liquid air.

The gaseous oxidation of acetone - II. The low-temperature reaction

1964 ◽  
Vol 279 (1377) ◽  
pp. 248-259 ◽  
Keyword(s):  
Low Temperature ◽  
Temperature Region ◽  
Low Temperatures ◽  
Peroxy Radical ◽  
Reaction Scheme ◽  
Methyl Radical ◽  
High Temperature Region ◽  
Region I ◽  
Methyl Hydroperoxide ◽  
Kinetics Of

The kinetics of the oxidation of acetone in the 'low-temperature’ region (i. e. below 320°C) have been carefully investigated. In contrast to the high-temperature region, the products include no methane, but appreciable quantities of methyl hydroperoxide as well as water, carbon monoxide and dioxide. A reaction scheme is suggested which involves degenerate chain branching by the homo­geneous decomposition of methyl hydroperoxide. The transition from the low-temperature mechanism to that prevailing at high tempera­tures is due to the changing importance of the alternative reactions of the methyl radical. At low temperatures, the formation of methyl hydroperoxide is favoured CH 3 + O 2 + M = CH 3 O 2 + M , CH 3 O 2 + R H = CH 3 O 2 H + R , whereas at high temperatures the methyl peroxy radical is too unstable to abstract hydro­gen and instead the reaction yields formaldehyde CH 3 + O 2 = HCHO + OH.

Evaluation of the Physical Properties of Rubber Vulcanizates at Low Temperatures

1946 ◽  
Vol 19 (4) ◽  
pp. 915-932
Author(s):  
L. Mullins
Keyword(s):  
Low Temperature ◽  
Physical Properties ◽  
Low Temperatures ◽  
Limited Range ◽  
Test Methods ◽  
Standard Test ◽  
Convenient Means ◽  
The Individual ◽  
Simple Character ◽  
Initial Results

Abstract The technical importance of rubber vulcanizates in fields where they are likely to be subjected to temperatures lower than normal requires no emphasis, and has resulted in considerable activity being directed to the evaluation of the physical properties of rubber vulcanizates at such temperatures. The purpose of these investigations has been to compare the low temperature serviceability of various rubbers, and to study of the behavior of the materials at these temperatures in order that the data obtained may be used to assist design. Such extension of knowledge is of great importance since rubber vulcanizates exhibit considerably increased stiffness and become brittle at low temperatures. Several good summaries of the work exist in the literature; these show that there is a considerable lack of uniformity in the methods of testing and representation. As a result of this wide diversity of test methods, there is no generally accepted index of low-temperature serviceability. Many of the tests which have been used involve the extension of the usual technical tests to lower temperatures, whereas others involve a study of the performance of rubber components in conditions of service. The results of such tests generally have been quoted as a temperature below which a particular property fails to fulfil a given requirement. The endeavor to obtain one temperature or one parameter which characterizes the resistance to low temperatures has been only partially successful, since the interdependence of stress, strain, time and temperature make it impossible to formulate relations of a simple character which describe the behavior of rubber vulcanizates over even a limited range of conditions. First, there is the need for an accepted standard test (or tests) ; secondly there is the need for a convenient method of expressing the resistance to low temperatures, and lastly, there is the need for the development of the ideas of the processes leading to the changes in physical properties at low temperatures. In this paper it is intended to review the various methods which have been suggested for low-temperature testing, to indicate the sources of the inadequacy of the individual tests, and to describe the initial results of an investigation, as yet incomplete, into a convenient means of testing and representing the mechanical properties at low temperatures.

Calculation of the Partition Function of a Double Minimum Oscillator from a Modified Variation Perturbation Method

1996 ◽  
Vol 51 (4) ◽  
pp. 249-256 ◽  
Author(s):  
Gerhard Taubmann
Keyword(s):  
Perturbation Theory ◽  
High Temperature ◽  
Partition Function ◽  
Low Temperature ◽  
Perturbation Method ◽  
Temperature Region ◽  
Low Temperatures ◽  
Reference Oscillator ◽  
Minimum Potential

Abstract The partition function of a double minimum oscillator is evaluated by means of variation perturbation theory. For low temperatures, the method cannot be applied in the usual way. Even for a symmetric double minimum potential VDM(x), the shift of the harmonic reference oscillator is not always zero as expected, but its minimum is near one of the minima of VDM(x) at low temperatures. The partition function thus calculated is only half the correct value. For sufficiently high temperature, the method works normally. The anomaly in the low temperature region is investigated in detail, and a modification of the variation perturbation method is suggested which eliminates most of the problems.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

Low-temperature limit of the rate of propagation of chains in the hydrobromination of ethylene

1979 ◽  
Vol 76 ◽  
pp. 1013-1015 ◽  
Author(s):  
D.P. Kiryukhin ◽  
I.M. Barkalov ◽  
V.l. Goldanskii
Keyword(s):  
Low Temperature ◽  
Temperature Limit
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