Measured temperature and pressure dependence of compressional (Vp) and shear (Vs) wave speeds in compacted, polycrystalline ice Ih

2003 ◽  
Vol 81 (1-2) ◽  
pp. 81-87 ◽  
Author(s):  
M B Helgerud ◽  
W F Waite ◽  
S H Kirby ◽  
A Nur
Keyword(s):  
Shear Wave ◽  
Compressional Wave ◽  
Measured Temperature ◽  
Shear Moduli ◽  
Wave Speeds ◽  
Shear Wave Speed ◽  
Polycrystalline Ice ◽  
Small Grains ◽  
Fixed End ◽  
Fraction Porosity

We report on laboratory measurements of compressional- and shear-wave speeds in a compacted, polycrystalline ice-Ih sample. The sample was made from triply distilled water that had been frozen into single crystal ice, ground into small grains, and sieved to extract the 180–250 µm diameter fraction. Porosity was eliminated from the sample by compacting the granular ice between a hydraulically driven piston and a fixed end plug, both containing shear-wave transducers. Based on simultaneous compressional- and shear-wave-speed measurements, we calculated Poisson's ratio and compressional-wave, bulk, and shear moduli from –20 to –5°C and 22 to 33 MPa. PACS Nos.: 91.60Lj

Measured temperature and pressure dependence of Vp and Vs in compacted, polycrystalline sI methane and sII methane–ethane hydrate

2003 ◽  
Vol 81 (1-2) ◽  
pp. 47-53 ◽  
Author(s):  
M B Helgerud ◽  
W F Waite ◽  
S H Kirby ◽  
A Nur
Keyword(s):  
High Pressure ◽  
Shear Wave ◽  
Pressure Dependence ◽  
Gas Hydrate ◽  
Pressure Vessel ◽  
Wave Speed ◽  
Measured Temperature ◽  
Shear Wave Speed ◽  
Temperature And Pressure ◽  
Fixed End

We report on compressional- and shear-wave-speed measurements made on compacted polycrystalline sI methane and sII methane–ethane hydrate. The gas hydrate samples are synthesized directly in the measurement apparatus by warming granulated ice to 17°C in the presence of a clathrate-forming gas at high pressure (methane for sI, 90.2% methane, 9.8% ethane for sII). Porosity is eliminated after hydrate synthesis by compacting the sample in the synthesis pressure vessel between a hydraulic ram and a fixed end-plug, both containing shear-wave transducers. Wave-speed measurements are made between –20 and 15°C and 0 to 105 MPa applied piston pressure. PACS No.: 61.60Lj

Sensitivity of the Shear Wave Speed-Stress Relationship to Soft Tissue Material Properties and Fiber Alignment

2021 ◽  
Author(s):  
Jonathon Blank ◽  
Darryl Thelen ◽  
Matthew S. Allen ◽  
Joshua Roth
Keyword(s):  
Wave Propagation ◽  
Shear Modulus ◽  
Shear Wave ◽  
Wave Speed ◽  
Axial Stress ◽  
Beam Model ◽  
Fiber Alignment ◽  
Wave Speeds ◽  
Shear Wave Speed ◽  
Constitutive Properties

The use of shear wave propagation to noninvasively gauge material properties and loading in tendons and ligaments is a growing area of interest in biomechanics. Prior models and experiments suggest that shear wave speed primarily depends on the apparent shear modulus (i.e., shear modulus accounting for contributions from all constituents) at low loads, and then increases with axial stress when axially loaded. However, differences in the magnitudes of shear wave speeds between ligaments and tendons, which have different substructures, suggest that the tissue’s composition and fiber alignment may also affect shear wave propagation. Accordingly, the objectives of this study were to (1) characterize changes in the apparent shear modulus induced by variations in constitutive properties and fiber alignment, and (2) determine the sensitivity of the shear wave speed-stress relationship to variations in constitutive properties and fiber alignment. To enable systematic variations of both constitutive properties and fiber alignment, we developed a finite element model that represented an isotropic ground matrix with an embedded fiber distribution. Using this model, we performed dynamic simulations of shear wave propagation at axial strains from 0% to 10%. We characterized the shear wave speed-stress relationship using a simple linear regression between shear wave speed squared and axial stress, which is based on an analytical relationship derived from a tensioned beam model. We found that predicted shear wave speeds were both in-range with shear wave speeds in previous in vivo and ex vivo studies, and strongly correlated with the axial stress (R2 = 0.99). The slope of the squared shear wave speed-axial stress relationship was highly sensitive to changes in tissue density. Both the intercept of this relationship and the apparent shear modulus were sensitive to both the shear modulus of the ground matrix and the stiffness of the fibers’ toe-region when the fibers were less well-aligned to the loading direction. We also determined that the tensioned beam model overpredicted the axial tissue stress with increasing load when the model had less well-aligned fibers. This indicates that the shear wave speed increases likely in response to a load-dependent increase in the apparent shear modulus. Our findings suggest that researchers may need to consider both the material and structural properties (i.e., fiber alignment) of tendon and ligament when measuring shear wave speeds in pathological tissues or tissues with less well-aligned fibers.

Shear Wave Speeds Track Axial Stress in Porcine Collateral Ligaments

2019 ◽  
Author(s):  
Jonathon Blank ◽  
Darryl Thelen ◽  
Joshua Roth
Keyword(s):  
Shear Wave ◽  
Wave Speed ◽  
Ex Vivo ◽  
Axial Stress ◽  
Axial Loading ◽  
Orthopedic Procedures ◽  
Stress Distributions ◽  
Collateral Ligaments ◽  
Wave Speeds ◽  
Shear Wave Speed

Ligament tension is an important factor that can affect the success of total knee arthroplasty (TKA) procedures. However, surgeons currently lack objective approaches for assessing tension in a particular ligament intraoperatively. The purpose of this study was to investigate the use of noninvasive shear wave tensiometry to characterize stress in medial and lateral collateral ligaments (MCLs and LCLs) ex vivo. Nine porcine MCL and LCL specimens were subjected to cyclic axial loading while wave speeds were measured using laser vibrometry. We found that squared shear wave speed increased linearly with stress in both the MCL (r2avg = 0.94) and LCL (r2avg = 0.98). Wave speeds were slightly lower in the MCL than the LCL when subjected to comparable axial stress (p < 0.001). Ligament-specific wave speeds may arise from differences in geometry and stress distributions between ligaments. These observations suggest it may be feasible to use noninvasive shear wave speed measures as a proxy of ligament loading during orthopedic procedures such as TKA.

PRECISION CORRELATIONS BETWEEN THE GEOACOUSTIC PARAMETERS OF AN UNCONSOLIDATED, SANDY MARINE SEDIMENT

2001 ◽  
Vol 09 (01) ◽  
pp. 101-123 ◽  
Author(s):  
MICHAEL J. BUCKINGHAM
Keyword(s):  
Shear Wave ◽  
Marine Sediment ◽  
Wave Speed ◽  
Wave Attenuation ◽  
Compressional Wave ◽  
Sandy Sediment ◽  
Shear Wave Speed ◽  
Causal Connections ◽  
Highly Correlated ◽  
Wave Properties

A recently introduced theoretical model of wave propagation in an unconsolidated, sandy marine sediment is discussed in this article. Essentially, the model consists of four analytical expressions, which specify four wave properties of the sediment, namely the speed and attenuation of the compressional and the shear wave. These expressions contain just three unknown constants, which must be evaluated from data. A technique is described in which these constants are determined from measured values of the compressional wave speed, the shear wave speed, and the shear wave attenuation. This technique is applied to preliminary data from O.N.R.s SAX'99 recent experiment on a sandy sediment in the Gulf of Mexico. From the fully specified equations, the fourth wave property, the attenuation of the compressional wave, is computed and found to lie within 0.5 dB/m of the measured value. Based on this limited evidence, it appears that the wave properties of an unconsolidated sediment are highly correlated and predictable. According to the theory, the causal connections between the wave properties originate in the sliding of one micro/asperity against another on the surfaces of contact between contiguous grains in the medium.

scholarly journals Shear wave cardiovascular MR elastography using intrinsic cardiac motion for transducer-free non-invasive evaluation of myocardial shear wave velocity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marian Amber Troelstra ◽  
Jurgen Henk Runge ◽  
Emma Burnhope ◽  
Alessandro Polcaro ◽  
Christian Guenthner ◽  
...  
Keyword(s):  
Healthy Volunteers ◽  
Shear Wave ◽  
Wave Speed ◽  
Shear Waves ◽  
Valve Closure ◽  
Limits Of Agreement ◽  
Wave Speeds ◽  
Shear Wave Speed ◽  
Non Invasive ◽  
Aortic Valve Closure

AbstractChanges in myocardial stiffness may represent a valuable biomarker for early tissue injury or adverse remodeling. In this study, we developed and validated a novel transducer-free magnetic resonance elastography (MRE) approach for quantifying myocardial biomechanics using aortic valve closure-induced shear waves. Using motion-sensitized two-dimensional pencil beams, septal shear waves were imaged at high temporal resolution. Shear wave speed was measured using time-of-flight of waves travelling between two pencil beams and corrected for geometrical biases. After validation in phantoms, results from twelve healthy volunteers and five cardiac patients (two left ventricular hypertrophy, two myocardial infarcts, and one without confirmed pathology) were obtained. Torsional shear wave speed in the phantom was 3.0 ± 0.1 m/s, corresponding with reference speeds of 2.8 ± 0.1 m/s. Geometrically-biased flexural shear wave speed was 1.9 ± 0.1 m/s, corresponding with simulation values of 2.0 m/s. Corrected septal shear wave speeds were significantly higher in patients than healthy volunteers [14.1 (11.0–15.8) m/s versus 3.6 (2.7–4.3) m/s, p = 0.001]. The interobserver 95%-limits-of-agreement in healthy volunteers were ± 1.3 m/s and interstudy 95%-limits-of-agreement − 0.7 to 1.2 m/s. In conclusion, myocardial shear wave speed can be measured using aortic valve closure-induced shear waves, with cardiac patients showing significantly higher shear wave speeds than healthy volunteers. This non-invasive measure may provide valuable insights into the pathophysiology of heart failure.

Reconciling elasticity tensor constraints from mineral physics and seismological observations: applications to the Earth’s inner core

2020 ◽  
Vol 222 (2) ◽  
pp. 1135-1145
Author(s):  
Brent G Delbridge ◽  
Miaki Ishii
Keyword(s):  
Shear Wave ◽  
Elastic Constants ◽  
Wave Speed ◽  
Inner Core ◽  
Body Wave ◽  
Elasticity Tensor ◽  
The Body ◽  
Wave Speeds ◽  
Mineral Physics ◽  
Shear Wave Speed

SUMMARY This study establishes the proper framework in which to compare seismic observations with mineral physics constraints for studies of the inner core by determining how the elements of the elasticity tensor are sampled by the normal modes of the Earth. The obtained mapping between the elements of the elasticity tensor and the seismic wave speeds shows that the choice of averaging scheme used to calculate isotropic properties is crucial to understand the composition of the inner core, especially for comparison with the shear wave speed such as that provided in PREM. For example, the appropriate shear wave speed calculated for an Fe-Ni-Si hcp alloy at inner-core conditions differs from the shear wave speed obtained by taking a Reuss average by as much as $27\, {\rm per\, cent}$. It is also shown for the first time that by combining the isotropic observations based upon normal-mode characteristic frequencies and anisotropic parameters from their splitting, the five independent elastic parameters (A, C, F, L and N) that fully describe a transversely isotropic inner core can be uniquely constrained. The elastic values based upon a variety of mode-splitting studies are reported, and the differences between models from various research groups are shown to be relatively small ($\lt 10\, {\rm per\, cent}$). Additionally, an analogous body-wave methodology is developed to approximately estimate the five independent elastic constants from observations of compressional wave traveltime anomalies. The body-wave observations are utilized to consider the depth dependence of inner-core anisotropy, in particular, the structure of the innermost inner core. Finally, we demonstrate that substantial errors may result when attempting to relate seismically observed P and S wave speeds from Debye velocities obtained through nuclear resonant inelastic X-ray scattering. The results of these experiments should be compared directly with the Debye velocity calculated from seismically constrained elastic constants. This manuscript provides a new set of formulae and values of seismic observations of the inner core that can be easily compared against mineral physics constraints for better understanding of the inner-core composition.

Antiplane Slip and Bonded Contact Waves at a Planar Interface Between Two Elastic Layers

2017 ◽  
Vol 84 (10) ◽  
Author(s):  
K. Ranjith
Keyword(s):  
Phase Velocity ◽  
Shear Wave ◽  
Wave Speed ◽  
Planar Interface ◽  
Interfacial Wave ◽  
Wave Speeds ◽  
Shear Wave Speed ◽  
Antiplane Elasticity ◽  
Elasticity Solutions ◽  
Elastic Layers

Interfacial wave solutions for a planar interface between two finite layers have been obtained within the framework of antiplane elasticity. Solutions are found to exist both for slipping contact and for bonded contact at the interface. Both the slip and bonded contact waves are found to be dispersive and multivalued. One family of slip and bonded contact waves is found with phase velocity in between the shear wave speeds of the two solids. It is also found that two families of slip and bonded contact waves exist with phase velocity greater than the shear wave speed of both solids.

scholarly journals Fluid effects on shear waves in finely layered porous media

Geophysics ◽  
2005 ◽  
Vol 70 (2) ◽  
pp. N1-N15 ◽  
Author(s):  
James G. Berryman
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Speed ◽  
Shear Waves ◽  
Ultrasonic Waves ◽  
Layered System ◽  
Pore Fluids ◽  
Shear Moduli ◽  
Shear Wave Speed ◽  
Shear Energy

Although there are five effective shear moduli for any layered transversely isotropic with a vertical symmetry axis (VTI) medium, one and only one effective shear modulus of the layered system (namely, the uniaxial shear) contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude of shear energy stored in this modulus by an amount that ranges from the smallest to the largest effective shear moduli of the VTI system. But since there are five shear moduli in play, the overall increase in shear energy due to fluids is reduced by a factor of about five in general. We can, therefore, give definite bounds on the maximum increase of overall shear modulus — about 20% of the allowed range as liquid is fully substituted for gas. An attendant increase of density (depending on porosity and fluid density) by approximately 5–10% decreases the shear-wave speed and thereby partially offsets the effect of this shear modulus increase. The final result is an increase of shear-wave speed on the order of 5–10%. This increase is shown to be possible under most favorable circumstances, that is, when the shear modulus fluctuations are large (resulting in strong anisotropy) and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well logging or laboratory experiments), resulting short response times also produce the requisite undrained behavior; therefore, fluids also affect shear waves at high frequencies by increasing rigidity.

Determination of compressional wave and shear wave speed profiles in sea ice by crosshole tomography—Theory and experiment

1993 ◽  
Vol 93 (2) ◽  
pp. 721-738 ◽  
Author(s):  
Subramaniam D. Rajan ◽  
George V. Frisk ◽  
James A. Doutt ◽  
Cynthia J. Sellers
Keyword(s):  
Sea Ice ◽  
Shear Wave ◽  
Wave Speed ◽  
Compressional Wave ◽  
Shear Wave Speed ◽  
Theory And Experiment
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