scholarly journals Universal G′ ∼ L–3 Law for the Low-Frequency Shear Modulus of Confined Liquids

2021 ◽  
pp. 650-657
Author(s):  
Alessio Zaccone ◽  
Laurence Noirez
Keyword(s):  
Shear Modulus ◽  
Low Frequency ◽  
Confined Liquids

scholarly journals Moduli and modes in the Mikado model

Soft Matter ◽  
2021 ◽  
Author(s):  
Brian Tighe ◽  
Karsten Baumgarten
Keyword(s):  
Shear Modulus ◽  
Mechanical Model ◽  
Low Frequency ◽  
Vibrational Modes ◽  
Prior Work ◽  
Fiber Networks ◽  
Elastic Shear Modulus ◽  
Flexible Fiber ◽  
Elastic Shear

We determine how low frequency vibrational modes control the elastic shear modulus of Mikado networks, a minimal mechanical model for semi-flexible fiber networks. From prior work it is known that...

scholarly journals Low frequency shear modulus of bcc3He below 1 K

2009 ◽  
Vol 150 (3) ◽  
pp. 032100 ◽  
Author(s):  
O Syshchenko ◽  
J Beamish
Keyword(s):  
Shear Modulus ◽  
Low Frequency

Low-frequency seismic properties of thermally cracked and argon-saturated granite

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. F147-F159 ◽  
Author(s):  
Cao Lu ◽  
Ian Jackson
Keyword(s):  
Shear Modulus ◽  
Transient Flow ◽  
Crack Density ◽  
Fluid Pressure ◽  
Low Frequency ◽  
Confining Pressure ◽  
Seismic Properties ◽  
Aspect Ratios ◽  
In Situ Permeability

Torsional forced-oscillation techniques have been used to measure the shear modulus and strain-energy dissipation on cylindrical specimens of a fine-grained granite, Delegate aplite. The specimens were subjected to thermal cycling and associated microcracking under varying conditions of confining pressure [Formula: see text] and argon pore-fluid pressure [Formula: see text] within the low-frequency saturated isobaric regime. Complementary transient-flow studies of in-situ permeability and volumetric measurements of connected crack porosity allowed the modulus measurements to be interpreted in terms of the density and interconnectivity of the thermally generated cracks. The modulus measurements indicate that newly generated thermal cracks are closed by a differential pressure, [Formula: see text], which ranges from [Formula: see text] for temperatures of [Formula: see text]. This suggests crack aspect ratios on the order of [Formula: see text]. The covariation of in-situ permeability [Formula: see text] and thermal crack density [Formula: see text] that we infer from the modulus deficit is consistent with percolation theory. There is a well-defined threshold at [Formula: see text], beyond which [Formula: see text] increases markedly as [Formula: see text], with [Formula: see text]. At lower crack densities, it is difficult to measure the sensitivity of shear modulus to variations of confining and pore pressures because pore-pressure equilibrium is approached so sluggishly. At temperatures beyond the percolation threshold, the modulus variation is a function of the effective pressure, [Formula: see text], with the value of [Formula: see text] increasing toward one with increasing crack connectivity.

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>

scholarly journals Experimental development of low-frequency shear modulus and attenuation measurements in mated rock fractures: Shear mechanics due to asperity contact area changes with normal stress

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. M19-M36 ◽  
Author(s):  
Seth Saltiel ◽  
Paul A. Selvadurai ◽  
Brian P. Bonner ◽  
Steven D. Glaser ◽  
Jonathan B. Ajo-Franklin
Keyword(s):  
Shear Modulus ◽  
Normal Stress ◽  
Contact Area ◽  
Fractured Reservoirs ◽  
Low Frequency ◽  
Real Contact Area ◽  
Rock Fractures ◽  
Asperity Contact ◽  
Experimental Development ◽  
Real Contact

Reservoir core measurements can help guide seismic monitoring of fluid-induced pressure variations in tight fractured reservoirs, including those targeted for supercritical [Formula: see text] injection. We have developed the first seismic-frequency “room-dry” measurements of fracture-specific shear stiffness, using artificially fractured standard granite samples with different degrees of mating, a well-mated tensile fracture from a dolomite reservoir core, as well as simple roughened polymethyl methacrylate (PMMA) surfaces. We have adapted a low-frequency (0.01–100 Hz) shear modulus and attenuation apparatus to explore the seismic signature of fractures and understand the mechanics of asperity contacts under a range of normal stress conditions. Our instrument is unique in its ability to measure at low-normal stresses (0.5–20 MPa), simulating “open” fractures in shallow or high-fluid-pressure reservoirs. The accuracy of our instrument is demonstrated by calibration and comparison with ultrasonic measurements and low-frequency direct shear measurements of intact samples from the literature. Pressure-sensitive film was used to measure real contact area of the fracture surfaces. The fractured shear modulus for most of the samples shows an exponential dependence on the real contact area. A simple numerical model, with one bonded circular asperity, predicts this behavior and matches the data for the simple PMMA surfaces. The rock surfaces reach their intact moduli at lower contact area than the model predicts, likely due to more complex geometry. Finally, we apply our results to a linear-slip interface model to estimate reflection coefficients and calculate S-wave time delays due to the lower-wave velocities through the fractured zone. We find that cross-well surveys could detect even well-mated hard-rock fractures, assuming the availability of high-repeatability acquisition systems.

scholarly journals Low-frequency (105 Hz) shear modulus of nanosuspension

2021 ◽  
Vol 1198 (1) ◽  
pp. 012001
Author(s):  
B B Badmaev ◽  
T S Dembelova ◽  
D N Makarova ◽  
S A Balzhinov ◽  
E D Vershinina
Keyword(s):  
Wave Propagation ◽  
Shear Modulus ◽  
Silica Nanoparticles ◽  
Shear Wave ◽  
Colloidal Suspension ◽  
Wave Length ◽  
Low Frequency ◽  
Resonance Method ◽  
Acoustic Resonance ◽  
Ultrasonic Interferometer

Abstract The low-frequency shear wave propagation in a suspension of silica nanoparticles in a polyethylsiloxane liquid was studied. The shear wave length was measured on ultrasonic interferometer, and it is equal to 55 μm. The value of the tangent of the mechanical losses angle is determined to be 0.18. These parameters were used to calculate the shear modulus of the investigated colloidal suspension; its value is 0.15‒105 Pa. The results obtained are in quite agreement with the data obtained by another way of the acoustic resonance method.

Local Viscoelasticity of Biopolymer Solutions

1996 ◽  
Vol 463 ◽  
Author(s):  
B. Schnurr ◽  
F. Gittes ◽  
P. D. Olmsted ◽  
C. F. Schmidt ◽  
F. C. Mackintosh
Keyword(s):  
Shear Modulus ◽  
Low Frequency ◽  
Thermal Fluctuations ◽  
High Frequency Power ◽  
Scaling Exponents ◽  
Complex Shear ◽  
High Resolution Technique ◽  
Micrometer Scale ◽  
The Relationship ◽  
Frequency Power

AbstractWe describe a new, high-resolution technique for determining the local viscoelastic response of polymer gels on a micrometer scale. This is done by monitoring thermal fluctuations of embedded probe particles. We derive the relationship between the amplitude of fluctuations and the low-frequency storage modulus G′, as well as the relationship between the fluctuation power spectrum, measured between 0.1 Hz and 25kHz, and the complex shear modulus G((ω). For both, semiflexible F-actin solutions and flexible polyacrylamide (PAAm) gels we observe high-frequency power-law dependence in the spectra, which reflects the behavior of the shear modulus. However, we observe distinctly different scaling exponents for G((ω) in F-actin and PAAm gels—presumably due to the semiflexible nature of the actin filaments.

scholarly journals Random Dynamic Response Characteristics of Pipeline Subjected to Blasting Cylindrical SH Waves

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Shiwei Lu ◽  
Heng Zhang ◽  
Ling Ji
Keyword(s):  
Shear Modulus ◽  
Plane Wave ◽  
Dynamic Response ◽  
Low Frequency ◽  
Simulation Method ◽  
Dominant Frequency ◽  
Sh Wave ◽  
Frequency Wave ◽  
Response Characteristics ◽  
Dynamic Response Characteristics

It is essential to investigate the influence of blasting vibrations on pipelines, and the dynamic response is the crux in the safety issues. At present, the blasting seismic wave is usually regarded as a plane wave. However, there is little research about the dynamic response characteristics of underground structures subjected to nonplane waves. The analytical solution to dynamic stress concentration factor (DSCF) of pipelines subjected to cylindrical SH wave was derived. Besides, the randomness of the shear modulus of soil was considered, and the statistical analysis of DSCF was carried out by the Monte Carlo simulation method. Results show that the variability of the shear modulus of soil has a significant influence on the probability distribution of DSCF. The larger the variation coefficient of the shear modulus is, the more obvious the skewness of DSCF is. The influence of low-frequency wave on pipeline increases with the reducing normalized distance r∗, while the influence of high-frequency wave reduces and the variation amplitude of DSCF increases. Compared with the DSCF of pipe subjected to a plane wave, a lower dominant frequency or larger normalized distance for the cylindrical SH wave will generate a more similar statistical characteristic of DSCF.

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