The Creep of Natural and Snythetic Rubber Compounds in Shear

1941 ◽  
Vol 14 (2) ◽  
pp. 433-443 ◽  
Author(s):  
Stuart H. Hahn ◽  
Ivan Gazdik
Keyword(s):  
Processing Technique ◽  
Creep Tests ◽  
Time Service ◽  
Wide Range ◽  
Recent Developments ◽  
Long Time ◽  
The Many ◽  
Short Time ◽  
Relative Creep ◽  
Rubberlike Materials

Abstract Creep tests, extending in some cases as long as 900 days, indicate that both natural and synthetic rubbers such as Neoprene and butadiene copolymer can be compounded to give satisfactory service in shear mountings. At 140° F, creep is from two to nine times greater than at 80° F, depending on the compound. Tests at room temperature do not indicate either the amount of creep or the life to be expected at higher temperatures. Actual creep (measured in inches) increases with stress, but when expressed at percentage of initial deflection, it may be independent of stress. Creep curves are linear over a considerable range of time when plotted on log-log scales. However, extrapolation of such curves to predict results after very long times is not justified, because the curves may not continue to be linear, or failure of the mountings may occur, particularly at high temperatures. Short time tests of any sort are not necessarily indicative of the relative creep or life of compounds in long-time service. The tests reported here are a small portion of a large number which is being continued and augmented. It is hoped that these and other investigations now under way may contribute to clearing the picture of the complex interrelations between the many physical properties of compounds of rubberlike materials. The rubber technologist uses his specialized knowledge to develop a wide variety of compounds, making use of several types of basic rubberlike materials. He chooses whichever fits service requirements best from performance and economic viewpoints. Modern materials and recent developments in processing technique have made possible compounds suitable for a wide range of service conditions.

A Comparison of Some Carbon Molybdenum Steels on the Basis of Various Creep Limits

1948 ◽  
Vol 159 (1) ◽  
pp. 165-172 ◽  
Author(s):  
A. E. Johnson ◽  
H. J. Tapsell
Keyword(s):  
Experimental Study ◽  
Experimental Work ◽  
Carbon Steels ◽  
Prolonged Heating ◽  
Time Service ◽  
Long Time ◽  
Engineering Materials ◽  
Short Time ◽  
The Relationship ◽  
Creep Limits

A previous report gave the results of an experimental study of the relationship between short-time and long-time creep limits of a number of carbon steels. Certain conclusions were drawn which it was realized were not necessarily applicable to other types of steel. Similar experimental work has since been carried out on six carbon molybdenum steels, and the results obtained indicate similar limitations in the applicability of short-time creep limits to estimation of design stresses for long-time service, as were disclosed by the prior tests on carbon steels. There is not, at first sight, any reason why short-time and long-time creep limits should correlate, since with most engineering materials metallurgical changes occur during prolonged heating.

scholarly journals Social and Economic Security in the System of State Protectedness

2019 ◽  
Vol 5 (4) ◽  
pp. 280-287
Author(s):  
D. Shvaiba
Keyword(s):  
Social Policy ◽  
Financial Economic ◽  
Economic Security ◽  
Political Preferences ◽  
Wide Range ◽  
Deformation Processes ◽  
The Many ◽  
Short Time ◽  
The Impact ◽  
State Protection

Taking as a basis the scientific study of different concepts in the theory of security, it is necessary to assume that the inaccessibility of the threat in the absolute sense is impossible. In fact, there may not be a certain type of threat to a particular object in a specific period of time (if there is not yet or there is no longer a corresponding danger factor). It is necessary to take into account that interests are only a small part of a wide range of objects of state protection. This share differs subjectively and interacts with the implemented financial, economic and social policy, the productivity of which is largely dependent on the impact of individual groups of people and parties (based on socio–political preferences). In addition — it is quite a mobile category, which has the ability to change qualitatively. It is obvious that the danger is one of the many destructive moments of security, along with those of which have already been discussed, for example threat, challenge, risk, decline, crisis, cataclysm, destruction, deformation processes, etc. It is necessary to clarify that the danger in the context of the ‘security triad’ is always modified: in a short time, they have all chances to transform from the present into the probable and vice versa.

scholarly journals Spatial and temporal variations of the high-altitude cusp precipitation

2004 ◽  
Vol 22 (7) ◽  
pp. 2441-2450 ◽  
Author(s):  
Z. Němeček ◽  
J. Šimůnek ◽  
J. Šafránková ◽  
L. Přech
Keyword(s):  
Magnetic Field ◽  
High Altitude ◽  
Spatial Dispersion ◽  
Temporal Variations ◽  
Temporal Features ◽  
Spatial Changes ◽  
Wide Range ◽  
Long Time ◽  
Field Lines ◽  
Short Time

Abstract. Structured dispersion patterns of the ion precipitation in low- and mid-altitude cusp regions have been reported by many authors. These patterns are interpreted either as temporal features in terms of the pulsed reconnection model or as spatial changes caused by a combination of the particle velocity with the convection of magnetic field lines. It is generally expected that the spatial dispersion is predominantly observed in lower altitudes where the spacecraft crosses a wide range of geomagnetic coordinates in a short time, whereas the high-altitude spacecraft observes temporal changes because it stays nearly on the same field line for a long time. We have analyzed one pass of the INTERBALL-1/MAGION-4 satellite pair through the high-altitude cusp and found that both temporal and spatial dispersion effects are important even in the magnetopause vicinity. The analysis of the present event shows a spatial nature of the observed dispersion in the LLBL and in the plasma mantle. We have identified two sources of a mantle precipitation operating simultaneously. Our investigations suggest that besides already reported latitudinal dispersion, the longitudinal dispersion can be observed during intervals of sufficiently high east-west interplanetary magnetic field component.

scholarly journals A Combined Exponential-Power-Law Method for Interconversion between Viscoelastic Functions of Polymers and Polymer-Based Materials

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3001
Author(s):  
Vitor Dacol ◽  
Elsa Caetano ◽  
João R. Correia
Keyword(s):  
Mechanical Response ◽  
Creep Compliance ◽  
Viscoelastic Behavior ◽  
Relaxation Modulus ◽  
Creep Tests ◽  
General Applicability ◽  
Wide Range ◽  
Long Time ◽  
Linear Viscoelastic ◽  
The Time Domain

Understanding and modeling the viscoelastic behavior of polymers and polymer-based materials for a wide range of quasistatic and high strain rates is of great interest for applications in which they are subjected to mechanical loads over a long time of operation, such as the self-weight or other static loads. The creep compliance and relaxation functions used in the characterization of the mechanical response of linear viscoelastic solids are traditionally determined by conducting two separate experiments—creep tests and relaxation tests. This paper first reviews the steps involved in conducting the interconversion between creep compliance and relaxation modulus in the time domain, illustrating that the relaxation modulus can be obtained from the creep compliance. This enables the determination of the relaxation modulus from the results of creep tests, which can be easily performed in pneumatic equipment or simple compression devices and are less costly than direct relaxation tests. Some existing methods of interconversion between the creep compliance and the relaxation modulus for linear viscoelastic materials are also presented. Then, a new approximate interconversion scheme is introduced using a convenient Laplace transform and an approximated Gamma function to convert the measured creep compliance to the relaxation modulus. To demonstrate the accuracy of the fittings obtained with the method proposed, as well as its ease of implementation and general applicability, different experimental data from the literature are used.

scholarly journals Creep Life Assessment of USC Boiler Tubes

2018 ◽  
Author(s):  
Keiji Kubushiro
Keyword(s):  
Life Assessment ◽  
Austenitic Steels ◽  
Ferritic Steels ◽  
Creep Life ◽  
Creep Tests ◽  
Life Evaluation ◽  
Boiler Tubes ◽  
Long Time ◽  
Creep Life Assessment ◽  
Short Time

CSEF (creep strength enhanced ferritic) steels and austenitic steels are widely used for USC boiler tubes. It is important to evaluate creep life of these parts because metal temperature is indeterminable in superheater and reheater tubes. Almost investigations were conducted under higher stress, short time creep tests, but the pressure for the boiler pipe and tube at actual plant were very low. It is therefore necessary to establish creep life method under long time region time test at various stresses. The purpose of this work is to establish creep life evaluation in high Cr ferritic steels and austenitic steels with long time creep ruptured data. The creep life evaluation methods are based on hardness and microstructure changes.

Classical Nucleation Theory and Its Application to Condensing Steam Flow Calculations

2005 ◽  
Vol 219 (12) ◽  
pp. 1315-1333 ◽  
Author(s):  
F Bakhtar ◽  
J B Young ◽  
A J White ◽  
D A Simpson
Keyword(s):  
Predictive Accuracy ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Droplet Radius ◽  
Droplet Growth ◽  
Wide Range ◽  
Recent Developments ◽  
Judicious Choice ◽  
The Many ◽  
Low Pressures

The paper discusses the classical theory of the homogeneous nucleation of water droplets from supersaturated vapour and its application in predicting condensation in steam nozzles. The first part consists of a review of classical nucleation theory, focusing on the many modifications made to the original Becker-Döring theory and providing some new insights into recent developments. It is concluded that the predictive accuracy required for engineering calculations is not yet attainable with a theory derived from first principles. The areas that require most attention relate to the properties of small molecular clusters and the energy transfer processes in the non-isothermal theory. Experiments in converging-diverging nozzles provide the best means for validation at the very high nucleation rates of interest, but measurements of pressure distribution and the Sauter mean droplet radius are insufficient to provide independent checks on the separate theories of nucleation and droplet growth. Nevertheless, a judicious choice for the nucleation rate equation, in combination with a standard droplet growth model and a suitable equation of state for steam, can provide accurate predictions over a wide range of conditions. The exception is at very low pressures where there is evidence that the droplet growth rate in the nucleation zone is underestimated.

A Comparison of Some Carbon Steels on the Basis of Various Creep Limits

1945 ◽  
Vol 153 (1) ◽  
pp. 169-179 ◽  
Author(s):  
A. E. Johnson ◽  
H. J. Tapsell
Keyword(s):  
Present Report ◽  
Carbon Steels ◽  
Rational Basis ◽  
Creep Tests ◽  
Satisfactory Performance ◽  
Long Time ◽  
Short Time ◽  
Creep Limits

The present report has been prepared with a view to determining whether any relationship exists between the results of the various short-time and long-time creep tests, which will permit the use of short-time tests, not merely as a means of separating good from bad steels, but also as the basis of design stresses intended to give satisfactory performance of the steel over working periods of considerable duration. Indications are given of some of the difficulties and limitations concerned in the use of short-time creep results in the case of carbon steels, and suggestions are made for some rational basis for steps which might be taken to offset these difficulties and limitations in applying the results of short-time tests to estimation of design stresses.

A Comprehensive Bibliography Of Professional Journal Articles On Accounting Information Systems

2001 ◽  
Vol 5 (3) ◽  
pp. 87-100
Author(s):  
Andrew D. Schiff ◽  
Michael K. Lavine
Keyword(s):  
Instructional Material ◽  
Systems Design ◽  
Accounting System ◽  
Certified Public Accountants ◽  
Journal Articles ◽  
Accounting Systems ◽  
Accounting Information Systems ◽  
Wide Range ◽  
Recent Developments ◽  
The Many

This paper lists and organizes 280 articles on a wide range of contemporary accounting system trends, issues and technologies. The articles have been selected from issues of eight leading professional accounting journals that have been published during the past five years. They are listed alphabetically within publication, and are then grouped by topic. In addition, the articles are referenced to the top ten accounting system technolo-gies, applications and issues identified by the American Institute of Certified Public Accountants (AICPA, 2000). This bibliography should be of interest to accounting sys-tem professors who wish to update their instructional material, and to accounting sys-tem researchers and practitioners who are seeking current explanations and analyses of the many recent developments in accounting systems design, implementation and operation.

Short-Time Tests for Long-Time Endurance

1923 ◽  
Vol 128 (4) ◽  
pp. 264-264
Author(s):  
J. W. Harsch
Keyword(s):  
Long Time ◽  
Short Time

The Problem of Identifying and Modeling the Relationship between Monetary Factor and Inflation in the Russian Economy

2008 ◽  
pp. 61-76
Author(s):  
A. Porshakov ◽  
A. Ponomarenko
Keyword(s):  
Money Supply ◽  
Money Demand ◽  
Russian Economy ◽  
Long Run ◽  
Complex Approach ◽  
Wide Range ◽  
Long Time ◽  
The Relationship ◽  
Supply Side Factors

The role of monetary factor in generating inflationary processes in Russia has stimulated various debates in social and scientific circles for a relatively long time. The authors show that identification of the specificity of relationship between money and inflation requires a complex approach based on statistical modeling and involving a wide range of indicators relevant for the price changes in the economy. As a result a model of inflation for Russia implying the decomposition of inflation dynamics into demand-side and supply-side factors is suggested. The main conclusion drawn is that during the recent years the volume of inflationary pressures in the Russian economy has been determined by the deviation of money supply from money demand, rather than by money supply alone. At the same time, monetary factor has a long-run spread over time impact on inflation.

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