scholarly journals Viscoelastic Behaviour from Complementary Forced-Oscillation and Microcreep Tests

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 721
Author(s):  
Ian Jackson
Keyword(s):  
Forced Oscillation ◽  
Relaxation Times ◽  
Experimental Methods ◽  
Creep Function ◽  
Relaxation Strength ◽  
Composite Modulus ◽  
Frequency Domains ◽  
New Strategy ◽  
Function Models ◽  
Transient And Steady State

There is an important complementarity between experimental methods for the study of high-temperature viscoelasticity in the time and frequency domains that has not always been fully exploited. Here, we show that the parallel processing of forced-oscillation data and microcreep records, involving the consistent use of either Andrade or extended Burgers creep function models, yields a robust composite modulus-dissipation dataset spanning a broader range of periods than either technique alone. In fitting this dataset, the alternative Andrade and extended Burgers models differ in their partitioning of strain between the anelastic and viscous contributions. The extended Burgers model is preferred because it involves a finite range of anelastic relaxation times and, accordingly, a well-defined anelastic relaxation strength. The new strategy offers the prospect of better constraining the transition between transient and steady-state creep or, equivalently, between anelastic and viscous behaviour.

scholarly journals Linearity and time-scale invariance of the creep function in living cells

2004 ◽  
Vol 1 (1) ◽  
pp. 91-97 ◽  
Author(s):  
Guillaume Lenormand ◽  
Emil Millet ◽  
Ben Fabry ◽  
James P. Butler ◽  
Jeffrey J. Fredberg
Keyword(s):  
Power Law ◽  
Time Scale ◽  
Relaxation Times ◽  
Cell Types ◽  
Creep Function ◽  
Scale Invariant ◽  
Time Constants ◽  
Frequency Domains ◽  
Power Law Exponent ◽  
The Matrix

We report here the creep function measured in three cell types, after a variety of interventions, and over three time decades (from 3ms to 3.2 s). In each case the response conformed to a power law, implying that no distinct molecular relaxation times or time constants could characterize the response. These results add to a growing body of evidence that stands in contrast to widely used viscoelastic models featuring at most a few time constants. We show instead that the ability of the matrix to deform is time-scale invariant and characterized by only one parameter: the power law exponent that controls the transition between solid-like and liquid-like behaviour. Moreover, we validate linearity by comparison of measurements in the time and frequency domains.

Investigation of Rotational Relaxation by Double Resonance and Stark Switch Techniques

1980 ◽  
Vol 35 (8) ◽  
pp. 832-840
Author(s):  
W. Schrepp ◽  
H. Dreizler ◽  
A. Guarnieri
Keyword(s):  
Double Resonance ◽  
Relaxation Times ◽  
Experimental Methods ◽  
Rotational Relaxation ◽  
Triple Resonance ◽  
Static Electric Field ◽  
First Order ◽  
Four Levels ◽  
Relative Change

Abstract For the four rotational levels JK₋K₊ = 101, 110,212 and 221 of ethylene oxide all possible four level double resonance experiments for dipole allowed transitions have been performed to investigate collisional effects and to determine the relative change of signal intensity, η = ⊿I/I, due to high power pump radiation. The T1 and T2-relaxation times have been measured for all dipole allowed transitions within these four levels. A combination of the data obtained from both experimental methods allows the determination of rate and bath constants taking into account only first order dipolar transitions. No further restrictions have been used. This approximation is supported by a triple resonance experiment. In addition to the pure gas investigation in the absence of external fields, rotational relaxation has been studied in the presence of a static electric field and in a mixture with hydrogen.

MACROSCOPIC BEHAVIOR OF ELECTRORHEOLOGICAL FLUIDS: TECHNIQUES FOR MEASURING RESPONSE TIME

1992 ◽  
Vol 06 (15n16) ◽  
pp. 2609-2623 ◽  
Author(s):  
KEITH D. WEISS ◽  
J. DAVID CARLSON
Keyword(s):  
Response Time ◽  
Channel Flow ◽  
Relaxation Times ◽  
Experimental Methods ◽  
Spectroscopic Technique ◽  
Electrorheological Fluids ◽  
Dielectric Data ◽  
Er Fluid ◽  
Measured Response ◽  
Good Agreement

Two experimental methods, a dielectric spectroscopic technique and a channel flow technique, have been found to provide reasonable estimates of an ER fluid's response time. The dielectric data obtained for an ER fluid was adequately modeled using a well established Cole-Cole relationship for a symmetric distribution of relaxation times. A calculation of the particle's conductivity in the ER fluid also was found to be possible using the measured dielectric data. The response time obtained with the channel flow technique was in good agreement with the measured response time of a working ER fluid device.

A Theory Relating Creep and Relaxation for Linear Materials With Memory

2010 ◽  
Vol 77 (3) ◽  
Author(s):  
R. C. Koeller
Keyword(s):  
Experimental Data ◽  
Fractional Calculus ◽  
Creep Compliance ◽  
Complex Modulus ◽  
Relaxation Times ◽  
Relaxation Modulus ◽  
Experimental Methods ◽  
Generalized Function ◽  
Materials With Memory ◽  
With Memory

The purpose of this paper is to suggest a linear theory of materials with memory, which gives a description for the similarities resulting when the various analytical and experimental methods used to reduce the creep and relaxation data are imposed on the observational changes in curvature that take place in both the creep compliance and relaxation modulus graphs. On a Log-Log graph both have one, two, or at most three pairs of changes in curvature depending on whether the material is a fluid or solid. These changes in curvature have been observed in many experiments and various regions have been discussed and classified. Section 1 gives a few of the many applications of fractional calculus to physical problems. In Sec. 2 an equation that contains both integration and differentiation is presented using geometrical observations about the relationship between the changes in curvature in the relaxation modulus and creep compliance based on published experiments. In Sec. 3 the generalized function approach to fractional calculus is given. In Sec. 4 a mechanical model is discussed. This model is able to share experimental data between the creep and relaxation functions, as well as the real and imaginary parts of the complex compliance or the complex modulus. This theory shares information among these three experimental methods into a unifying theory for solid materials when the loads are within the linear range. Under a limiting case, this theory can account for flow so that the material need not return to its original shape after the load is removed. The theory contains one physical parameter, which is related to the speed of sound and a group of phenomenological parameters that are functions of temperature and the composition of the material. These phenomenological parameters are relaxation times and creep times. This theory differs from the classical polynomial constitutive equations for linear viscoelasticity. It is a special case of Rabotnov’s equations and Torvik and Bagley’s fractional calculus polynomial equations, but it imposes symmetry conditions on the stress and strain when the material is a solid. Sections 56 are comments and conclusions, respectively. No experimental results are given at this time since this paper presents the foundations of materials with memory as related to experimental data. The introduction of experimental data to fit this theory will result in the breakdown of an important part of this research.

Dynamic Analysis for Rotors of a Twin-Screw Compressor with Gas-Induced Cyclic Loads

2015 ◽  
Vol 789-790 ◽  
pp. 220-225
Author(s):  
Yu Ren Wu ◽  
Van The Tran ◽  
Po Hua Hsu
Keyword(s):  
Multibody Dynamics ◽  
Noise Spectrum ◽  
Dynamics Simulation ◽  
Screw Compressor ◽  
Cyclic Loads ◽  
Frequency Domains ◽  
Dynamic Forces ◽  
New Strategy ◽  
Twin Screw ◽  
Screw Rotors

The effects of dynamic forces and elastic contacts in a pair of intermeshing rotors with the gas-induced cyclic loads based on the multibody dynamics simulation have not investigated yet. The comparison of numerical spectra of time and frequency domains of acceleration with the experimental noise spectrum of an oil-injected twin-screw compressor has not also considered. Therefore, this study proposes a new strategy, which combines the fluctuating torques and forces induced by cyclic gas pressure on the screw rotors to numerically predict vibration response in an oil-injected twin-screw compressor.

Low-frequency seismic properties of olivine-orthopyroxene mixtures

2020 ◽  
Author(s):  
Tongzhang Qu ◽  
Ian Jackson ◽  
Ulrich Faul
Keyword(s):  
Shear Modulus ◽  
Upper Mantle ◽  
Forced Oscillation ◽  
Low Frequency ◽  
Secondary Phase ◽  
Confining Pressure ◽  
Creep Function ◽  
Seismic Properties ◽  
New Findings

<p>Although the seismic properties of polycrystalline olivine have been the subject of systematic and comprehensive study at seismic frequencies, the role of orthopyroxene as the major secondary phase in the shallow parts of the Earth’s upper mantle has so far received little attention. Accordingly, we have newly prepared synthetic melt-free polycrystalline specimens containing different proportions of olivine (Ol, Fo<sub>90</sub>) and orthopyroxene (Opx, En<sub>90</sub>) by the solution-gelation method. The resulting specimens, ranging in composition between Ol<sub>95</sub>Opx<sub>5</sub> and Ol<sub>5</sub>Opx<sub>95</sub> composition, were mechanically tested by torsional forced oscillation at temperatures of 1200 ºC to 400 ºC accessed during staged cooling under a confining pressure of 200 MPa. The microstructures of tested specimens were evaluated by BSE, EBSD and TEM. The forced-oscillation data, i.e. shear modulus and associated strain-energy dissipation at 1-1000 s period, were closely fitted by a model based on an extended Burgers-type creep function. This model was also required to fit data from previous ultrasonic and Brillouin spectroscopic measurements at ns-µs periods. Within the observational window (1-1000 s), the shear modulus and dissipation vary monotonically with period and temperature for each of the tested specimens, which is broadly comparable with that previously reported for olivine-only samples. There is no evidence of the superimposed dissipation peak reported by Sundberg and Cooper (2010) for an Ol<sub>60</sub>Opx<sub>40</sub> specimen prepared from natural precursor materials and containing a melt fraction of 1.5%. The higher orthopyroxene concentrations are associated with systematically somewhat lower levels of dissipation and corresponding weaker modulus dispersion. The new findings suggest that the olivine-based model for high-temperature viscoelasticity in upper-mantle olivine requires only modest modification to accommodate the role of orthopyroxene, including appropriate compositional dependence of the unrelaxed modulus and its temperature derivative.</p>

Energy transfer and dynamical structure

1976 ◽  
Vol 9 (1) ◽  
pp. 21-33 ◽  
Author(s):  
Josef Eisinger
Keyword(s):  
Energy Transfer ◽  
Relaxation Times ◽  
Experimental Methods ◽  
Rotational Relaxation ◽  
Biological Macromolecules ◽  
Dynamical Structure ◽  
Analytical Instrument ◽  
Fluorescence Depolarization ◽  
X Ray ◽  
Molecular Weights

It is only some 50 years ago that biophysicists obtained reliable experimental methods for estimating the molecular weights of biological macromolecules, chiefly as a result of Svedberg's work in developing the ultracentrifuge as an analytical instrument (Svedberg & Pedersen, 1940). Having gained some understanding of the size of proteins, interest soon thereafter turned to the shape and rotational relaxation times of these molecules, and Perrin's work on fluorescence depolarization helped to lay the foundations there (Perrin, 1929). Biophysics had to wait for the development of X-ray spectroscopy of proteins and nucleic acids to provide a picture of the interior structure of biological macromolecules.

scholarly journals Poroelastic relaxation in thermally cracked and fluid-saturated glass

2020 ◽  
Author(s):  
Abdulwaheed Ògúnsàmì ◽  
Jan Borgomano ◽  
Jérôme Fortin ◽  
Ian Jackson
Keyword(s):  
Forced Oscillation ◽  
Axial Strain ◽  
Ambient Pressure ◽  
Torsional Oscillation ◽  
Relaxation Times ◽  
Continuous Distribution ◽  
Theoretical Models ◽  
Confining Pressure ◽  
Supporting Evidence ◽  
Aspect Ratios

<p>To test theoretical models of modulus dispersion and dissipation in fluid-saturated rocks, we have investigated the broadband mechanical properties of four thermally cracked glass specimens of simple microstructure with complementary forced-oscillation (0.004 -100 Hz) and ultrasonic techniques (~1MHz). Strong pressure dependence of moduli (bulk, Young’s, and shear), axial strain, and ultrasonic wave speeds for dry conditions, attests to essentially complete crack closure at a confining pressure of 15 MPa – indicative of ambient-pressure crack aspect ratios mainly < 2 ´ 10<sup>-4</sup>.Oscillation of the confining pressure reveals bulk modulus dispersion and a corresponding dissipation peak, near 2 mHz only at the lowest effective pressure (2.5 MPa) – attributed to the transition with increasing frequency from the drained to saturated-isobaric regime. The observations are consistent with Biot-Gassmann theory, with dispersion and dissipation adequately represented by a Zener model.  Above the draining frequency, axial forced-oscillation tests show dispersion of Young’s modulus and Poisson’s ratio, and an associated broad dissipation peak centred near 0.3 Hz, thought to reflect local ‘squirt’ flow and adequately modelled with a continuous distribution of relaxation times over two decades. Observations of Young’s and shear modulus dispersion and dissipation from complementary flexural and torsional oscillation measurements for differential pressure ≤ 10 MPa provide supporting evidence of the transition with increasing frequency from the saturated-isobaric to the saturated-isolated regime – also probed by the ultrasonic technique. These findings validate predictions from theoretical models of dispersion in cracked media and emphasize need for caution in the seismological application of laboratory ultrasonic data for cracked media.</p>

Reversible Photo-Induced Currents in Epitaxial Pb(Zr0.52Ti0.48)O3 Thin Films

1993 ◽  
Vol 310 ◽  
Author(s):  
J. Lee ◽  
S. Esayan ◽  
J. Prohaska ◽  
A. Safari
Keyword(s):  
Thin Films ◽  
Relaxation Times ◽  
Ferroelectric Thin Films ◽  
Pzt Thin Films ◽  
Pzt Films ◽  
Ferroelectric Memory ◽  
Induced Currents ◽  
First Time ◽  
Non Destructive ◽  
Transient And Steady State

AbstractThe pyroelectric and photogalvanic effects have been studied extensively in epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin films. For the first time, photo-induced currents, which were completely reversible by electrical voltage, were observed in ferroelectric thin films. The photo-induced currents exhibited transient and steady state components. The transient component, in turn, consisted of two components with fast (<1 µs) and slow (∼hours) relaxation times. The mechanisms of the photo-induced currents in PZT films and their possible application in non-destructive readout ferroelectric memory are discussed.

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