Analysis of the Dynamic Stress Relaxometer Test Geometry and Conversion of Relaxing-Torque Data to Frequency-Dependent Viscoelastic Properties

Abstract The test geometry of the DSR has been mathematically modeled to provide an adequate description of the strain (and stress) distribution within a test specimen. The consideration of three separate deformation regions were required. Two of these regions, not considered in previous models, contribute 27% to 59% (depending upon the user-selectable closure height) of the total measured torque exerted on the DSR rotor. The utility of this model has been demonstrated by the agreement between the stress relaxation data obtained by converting the DSR relaxing torque measurements, using the modeled form factor, and data obtained with a uniform-strain-deformation instrument (RMS with cone and plate fixture) for four elastomer samples. Furthermore, the transformation of the converted DSR stress relaxation data to the frequency domain revealed good agreement with the frequency-dependent shear loss and storage moduli and complex viscosity obtained from RMS oscillatory experiments.

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Drift and Relaxation of Rubber

Rubber Chemistry and Technology ◽

10.5254/1.3546677 ◽

1944 ◽

Vol 17 (3) ◽

pp. 576-596

Author(s):

M. Mooney ◽

W. E. Wolstenholme ◽

D. S. Villars

Keyword(s):

Stress Relaxation ◽

Initial Stress ◽

New Method ◽

Controlled Atmosphere ◽

Relaxation Data ◽

Additional Advantage ◽

Vulcanized Rubber ◽

Eyring Theory ◽

Modified Theory ◽

Good Agreement

Abstract Numerous studies have been published on the relaxation and drift, or creep, of soft vulcanized rubber. In the present work, tests of this kind have been extended considerably beyond previously published work, both as to duration of the test and range of the initial stress or elongation. Some compression drift tests have now been in progress for eight years. A new method of measuring stress relaxation at fixed elongation has been developed, particularly with the purpose of conserving space. This method has made it possible and practical to carry out a large number of tests, many of them lasting for many months. An additional advantage of the test is that the samples can be kept in a controlled atmosphere as well as at a controlled temperature. Some of the more extensive relaxation data have been used to test the Tobolsky-Eyring theory of relaxation. Good agreement is obtained by assuming two relaxation mechanisms. An alternative or modified theory of relaxation is presented.

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Reloading Stress Relaxation Behavior Analysis Based on a Creep Model for High Temperature Bolting Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.328.950 ◽

2013 ◽

Vol 328 ◽

pp. 950-954

Author(s):

Wei Wei Zhang ◽

Hong Xu ◽

Hong Yuan Li

Keyword(s):

High Temperature ◽

Stress Relaxation ◽

Steady State Creep ◽

Relaxation Behavior ◽

Creep Model ◽

National Research Institute ◽

Time Intervals ◽

Stress Relaxation Behavior ◽

Proposed Model ◽

Good Agreement

An analytical method based on a creep model is being developed to investigate the effect of retightening on stress relaxation behavior for high-temperature turbine and valve studs/bolts. In order to validate the approach, the calculated results are compared to the results of uniaxial reloading stress relaxation testing, which were performed by the National Research Institute for Metals of Japan (NRIM) for 12Cr-1Mo-1W-1/4V stainless steel bolting material at 550°C. It was shown that the proposed model based on Altenbach-Gorash-Naumenko creep model for the primary and steady state creep could be applied for the present data. The calculated residual stresses versus time curves were in good agreement with the measured for initial stress level of 273.6MPa at 550°C and for specific reloading time intervals of 24, 72, 240, and 720 hours.

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Visual Observations and Torque Measurements in the Taylor Vortex Regime Between Eccentric Rotating Cylinders

Journal of Lubrication Technology ◽

10.1115/1.3451499 ◽

1971 ◽

Vol 93 (1) ◽

pp. 121-129 ◽

Cited By ~ 12

Author(s):

P. Castle ◽

F. R. Mobbs ◽

P. H. Markho

Keyword(s):

Outer Cylinder ◽

Taylor Vortex ◽

Rotating Cylinders ◽

Taylor Vortices ◽

Torque Measurements ◽

Good Agreement ◽

Visual Observations

The instability of Taylor vortices in the flow between a stationary outer cylinder and an eccentric rotating inner cylinder has been investigated by visual observations and by torque measurements. It is shown that both a “weak” and “strong” wavy mode of instability can be detected by torque measurements, giving critical Taylor numbers in good agreement with visual observations.

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Isothermal Crystallization and Rheology Properties of Isotactic Polypropylene/Bacterial Cellulose Composite

Polymers ◽

10.3390/polym10111284 ◽

2018 ◽

Vol 10 (11) ◽

pp. 1284 ◽

Cited By ~ 3

Author(s):

Bo Wang ◽

Fu-hua Lin ◽

Xiang-yang Li ◽

Zhong-wei Zhang ◽

Xiao-rong Xue ◽

...

Keyword(s):

Bacterial Cellulose ◽

Storage Modulus ◽

Isotactic Polypropylene ◽

Crystallization Temperature ◽

Isothermal Crystallization ◽

Complex Viscosity ◽

Isothermal Crystallization Kinetics ◽

Interfacial Compatibility ◽

And Storage ◽

Better Than

Bacterial cellulose (BC) is a new kind of cellulose with great potential in enhancing preparation of isotactic Polypropylene (iPP) composites, which have been found with excellent performance. However, the interface compatibility between BC and iPP is poor. In this study, iPP/BC composites were prepared by solution mixing. Esterification modified BC (CO) and Maleic anhydride grafted polypropylene (MAPP) added as a compatibilizer was both used to improve the interfacial compatibility of the iPP/BC composites. The rheology and isothermal crystallization behavior of the composites was tested and discussed. The result shows that the complex viscosity and storage modulus of the composite significantly increase in the rule iPP, iPP/BC2, iPP/CO2, and M-iPP/BC3, which indicates that the compatibility of the composite increases as this rule. According to the isothermal crystallization kinetics result, the crystal growth mode of iPP was not affected by the addition of BC and the interfacial compatibility. The spherulite growth rate of the iPP/BC composite increases with increasing crystallization temperature. Especially, the value decreases as the same rule with the complex viscosity and storage modulus of the composite at the same isothermal crystallization temperature. These results suggest that the interface compatibility of iPP/BC composites is greatly improved and the interface compatibility of the M-iPP/BC3 is better than the iPP/CO2.

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Modeling the Effect of Water Activity, pH, and Temperature on the Probability of Enterotoxin A Production by Staphylococcus aureus

Journal of Food Protection ◽

10.4315/0362-028x.jfp-15-161 ◽

2016 ◽

Vol 79 (1) ◽

pp. 148-152 ◽

Cited By ~ 5

Author(s):

TIAN DING ◽

YAN-YAN YU ◽

CHENG-AN HWANG ◽

QING-LI DONG ◽

SHI-GUO CHEN ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Water Activity ◽

Storage Temperature ◽

Probability Model ◽

Toxin Production ◽

Factors Affecting ◽

Model Predictions ◽

And Storage ◽

Storage Temperatures ◽

Good Agreement

ABSTRACT The objectives of this study were to develop a probability model of Staphylococcus aureus enterotoxin A (SEA) production as affected by water activity (aw), pH, and temperature in broth and assess its applicability for milk. The probability of SEA production was assessed in tryptic soy broth using 24 combinations of aw (0.86 to 0.99), pH (5.0 to 7.0), and storage temperature (10 to 30°C). The observed probabilities were fitted with a logistic regression to develop a probability model. The model had a concordant value of 97.5% and concordant index of 0.98, indicating that the model satisfactorily describes the probability of SEA production. The model showed that aw, pH, and temperature were significant factors affecting the probability of toxin production. The model predictions were in good agreement with the observed values obtained from milk. The model may help manufacturers in selecting product pH and aw and storage temperatures to prevent SEA production.

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Including poroelastic effects in the linear slip theory

Geophysics ◽

10.1190/geo2014-0409.1 ◽

2015 ◽

Vol 80 (2) ◽

pp. A51-A56 ◽

Cited By ~ 11

Author(s):

J. Germán Rubino ◽

Gabriel A. Castromán ◽

Tobias M. Müller ◽

Leonardo B. Monachesi ◽

Fabio I. Zyserman ◽

...

Keyword(s):

Viscous Friction ◽

Seismic Wave Propagation ◽

Seismic Attenuation ◽

Porous Rocks ◽

Compliance Matrix ◽

Frequency Dependent ◽

Attenuation Mechanism ◽

Wave Induced ◽

Complex Valued ◽

Good Agreement

Numerical simulations of seismic wave propagation in fractured media are often performed in the framework of the linear slip theory (LST). Therein, fractures are represented as interfaces and their mechanical properties are characterized through a compliance matrix. This theory has been extended to account for energy dissipation due to viscous friction within fluid-filled fractures by using complex-valued frequency-dependent compliances. This is, however, not fully adequate for fractured porous rocks in which wave-induced fluid flow (WIFF) between fractures and host rock constitutes a predominant seismic attenuation mechanism. In this letter, we develop an approach to incorporate WIFF effects directly into the LST for a 1D system via a complex-valued, frequency-dependent fracture compliance. The methodology is validated for a medium permeated by regularly distributed planar fractures, for which an analytical expression for the complex-valued normal compliance is determined in the framework of quasistatic poroelasticity. There is good agreement between synthetic seismograms generated using the proposed recipe and those obtained from comprehensive, but computationally demanding, poroelastic simulations.

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Bulk Moduli from Physical Aging and Stress Relaxation Data

Progress and Trends in Rheology V ◽

10.1007/978-3-642-51062-5_216 ◽

1998 ◽

pp. 447-448

Author(s):

J. Vernel ◽

M. J. Kubát ◽

R. W. Rychwalski ◽

J. Kubat

Keyword(s):

Stress Relaxation ◽

Physical Aging ◽

Relaxation Data

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The Frequency Response of Electrochemical Wall Shear Probes in Pulsatile Flow

Journal of Biomechanical Engineering ◽

10.1115/1.3138643 ◽

1987 ◽

Vol 109 (1) ◽

pp. 60-64 ◽

Cited By ~ 9

Author(s):

L. Talbot ◽

J. J. Steinert

Keyword(s):

Mass Transfer ◽

Frequency Response ◽

Pulsatile Flow ◽

Straight Tube ◽

Asymptotic Results ◽

Frequency Dependent ◽

Shear Rates ◽

Pulsatile Flows ◽

Wall Shear ◽

Good Agreement

The frequency response of surface-mounted electrochemical mass transfer probes used to deduce wall shear rates has been investigated experimentally for the case of fully developed laminar pulsatile flow in a straight tube. Generally good agreement is found with the asymptotic results obtained by Lighthill’s methods. The significance of the results with regard to the investigation of models of pulsatile flows of physiological interest is discussed. It is concluded that the frequency-dependent phase and amplitude corrections required to obtain accurate wall shear measurements are of such magnitudes as to render impractical the use of electrochemical probes to determine wall shear rates in these flows.

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