Transverse Wave Speed Research Articles

Interior and Edge Elastic Waves in Graphene

Elastic waves propagating in graphene nanoribbons were studied using both continuum modeling and molecular dynamics simulations. The Mindlin's plate model was employed to model the propagation of interior waves of graphene, and a continuum beam model was proposed to model the propagation of edge waves in graphene. The molecular dynamics results demonstrated that the interior longitudinal and transverse wave speeds of graphene are about 18,450 m/s and 5640 m/s, respectively, in good agreement with the Mindlin's plate model. The molecular dynamics simulations also revealed the existence of elastic edge waves, which may be described by the proposed continuum beam model.

Acoustic manifestations of frozen bubbles

The hydrocarbon seeps emitting buoyant bubble plumes from seafloor vents have been actively investigated in different regions of the World Ocean. In winter, rising bubbles, which have reached the sea surface, freeze in ice. These clouds of the frozen bubbles are observed in Arctic seas and represent a common element of an ice cover of lakes. Deposits of gas hydrates were discovered in many marginal seas of the World Ocean. The nature of the relationship between the acoustic and physical properties of gas hydrates is still under debate for both saturated sediments and sediment containing free-gas bubbles. Acoustic manifestations of bubbles frozen in ice and gas hydrate are the subjects of the current study. On the basis of the general solution of the elastic wave scattering problem for the sphere, the scattering cross section for a bubble frozen in an ice has been found. The derived expressions coincide in the limiting cases with known results: a bubble in a rubber-like media, where the longitudinal wave speed is significantly faster than the transverse wave speed and an empty cavity in the elastic media. The structure of low-frequency resonances of bubbles clouds of the simplest geometry has been investigated.

Lithographically fabricated gratings for the interferometric measurement of material shear moduli under extreme conditions

Electron beam lithography and photolithography were used to fabricate diffraction gratings on targets for laser-driven shock-wave experiments. This target design was used with an optical interferometric system to measure transverse wave motion of the target during dynamic (shock-wave) compression. A wedged-shaped diamond substrate and reflective grating on the sample's surface allowed detection of transverse motion. Proof of principle tests on single-crystal 〈100〉 Si samples gave a transverse wave speed of 5.9 km/s at 5 GPa and a shear modulus of 81 GPa. This experimental design has tremendous potential, including the possibility of measuring the shear properties of pure iron at Earth core conditions.

Transverse Impact Response of a Linear Elastic Ballistic Fiber Yarn

Transverse impact response of a linear elastic Kevlar® KM2 fiber yarn was determined at various striking speeds from Hopkinson bar and gas gun experiments incorporated with high-speed photography techniques. Upon transverse impact, a triangle shape was formed in the fiber yarn. Both longitudinal and transverse waves were produced and propagated outwards the fiber yarn. Both the angle of the triangle and Euler transverse wave speed vary with striking speeds. The relationship between the Euler transverse wave speed and the striking speed was determined. The transverse impact response of the fiber yarn was also analyzed with a model, which agrees well with the experimental results. The model shows that the longitudinal wave speed is critical in the ballistic performance of the fiber yarn. At a certain striking speed, a higher longitudinal wave speed produces a higher Euler transverse wave speed, enabling us to spread the load and dissipate the impact energy faster, such that the ballistic performance of the fiber yarn is improved.

Improved low-frequency performance of a composite sound absorption coating

In order to improve the low-frequency acoustic performance, a composite sound absorption coating made by embedding another viscoelastic material into the viscoelastic substrate of the traditional sound absorption coating, has been developed. Compared to the substrate, the transverse wave speed of the embedded-layer is lower. Accounting for the symmetry, the unit cell of the traditional sound absorption coating or the composite sound absorption coating could be approximately regarded as a viscoelastic single-layer cylindrical tube or a viscoelastic double-layer cylindrical tube, respectively. The plane wave normally impinging on the sound absorption coating only excites the axisymmetric wave propagating in the axial direction of the viscoelastic cylindrical tube. If the complex axisymmetric wave number and the effective impedance of the viscoelastic cylindrical tube are obtained, the acoustic performance of the sound absorption coating could be evaluated by using the transfer matrix method, which is suitable for both the single-layer cylindrical tube and the double-layer cylindrical tube. Numerical results show that the peak frequency of the sound absorption coefficient is shifted to the lower location as the proportion of the embedded-layer increases, or the transverse wave speed of the embedded-layer decreases.

Anomalies in the temperature dependence of the contribution to the speed of sound from hybridized electronic states of transition element impurities

The temperature dependence of the speed of sound in crystalline mercury selenide with low concentrations of iron impurities is studied. Experiments are conducted in the ranges of concentration and temperature where hybridized electronic states in iron impurities have been observed previously. It is found that at temperatures below 10 K the speed of slow transverse ultrasonic waves has an anomalous nonmonotonic segment of its temperature variation that is related to the influence of the impurities and reflects the existence of hybridized states. The observed anomalies in the sound speed are described in terms of a theory for the electron contribution to the elastic moduli that includes hybridization of impurity states and electron-electron interactions. Fits of the theoretical dependences to the experimental data yield quantitative information on the parameters of the hybridized states and of the Fermi-liquid interaction.

A simple method for fabricating artificial kidney stones of different physical properties

A simple method for preparing artificial kidney stones with varying physical properties is described. BegoStone was prepared with a powder-to-water ratio ranging from 15:3 to 15:6. The acoustic properties of the phantoms were characterized using an ultrasound transmission technique, from which the corresponding mechanical properties were calculated based on elastic wave theory. The measured parameters for BegoStone phantoms of different water contents are: longitudinal wave speed (3,148-4,159 m/s), transverse wave speed (1,813-2,319 m/s), density (1,563-1,995 kg/m(3)), longitudinal acoustic impedance (4.92-8.30 kg/m(2) s), transverse acoustic impedance (2.83-4.63 kg/m(2) s), Young's modulus (12.9-27.4 GPa), bulk modulus (8.6-20.2 GPa), and shear modulus (5.1-10.7 GPa), which cover the range of corresponding properties reported in natural kidney stones. In addition, diametral compression tests were carried out to determine tensile failure strength of the stone phantoms. BegoStone phantoms with varying water content at preparation have tensile failure strength from 6.9 to 16.3 MPa when tested dry and 3.2 to 7.1 MPa when tested in water-soaked condition. Overall, it is demonstrated that this new BegoStone preparation method can be used to fabricate artificial stones with physical properties matched with those of natural kidney stones of various chemical compositions.

1812 IMPROVED STONE PHANTOMS FOR SHOCK WAVE LITHOTRIPSY

You have accessJournal of UrologyStone Disease: SWL, Ureteroscopic or Percutaneous Stone Removal III1 Apr 20101812 IMPROVED STONE PHANTOMS FOR SHOCK WAVE LITHOTRIPSY Michael Lipkin, Dorit Zilberman, Neal Simmons, Eric Esch, Glenn Preminger, and Pei Zhong Michael LipkinMichael Lipkin More articles by this author , Dorit ZilbermanDorit Zilberman More articles by this author , Neal SimmonsNeal Simmons More articles by this author , Eric EschEric Esch More articles by this author , Glenn PremingerGlenn Preminger More articles by this author , and Pei ZhongPei Zhong More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.1737AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES BegoStone plaster has been used as a stone phantom material for shock-wave lithotripsy (SWL) research because of its physical similarity to calcium oxalate monohydrate. However, human stones vary in composition and physical properties. The purpose of this study was to develop a BegoStone phantom that would closely mimic the properties of other types of human stones. The ratio of BegoStone powder to water was varied and the tensile strength, longitudinal wave speed, and transverse wave speeds were measured for the resulting samples. METHODS BegoStone powder was mixed water in varying ratios (15:3, 15:4, 15:5, 15:6). The samples molded into 5mm x 10mm cylindrical stones and subsequently sectioned for either acoustic or tensile testing. Tensile strength was determined using a diametral compression fixture on a universal testing machine. Longitudinal and wave speeds were determined by measuring the propagation time of an ultrasound pulse in a sample of known thickness. RESULTS The phantom tensile strength decreased as the powder:water ratio decreased (15:3–7MPa, 15:4–5MPa, 15:5–3.8 MPa, 15:6–3.2MPa). Longitudinal wave speeds decreased with increased water (15:3-8.2•106Kg/m2s, 15:4-6.4•106Kg/m2s, 15:5-5.2•106Kg/m2s, 15:6-4.9•106Kg/m2s) with transverse wave speed following a similar trend (15:3-4.6•106Kg/m2s, 15:4-3.5•106Kg/m2s, 15:5-3.1•106Kg/m2s, 15:6-2.8•106Kg/m2s). CONCLUSIONS The range of physical properties produced with powder to water ratios of 15:3 to 15:6 matches those of human kidney stones. A stone phantom possessing the physical and acoustic properties similar human kidneys stones can be produced with different BegoStone powder to water ratios: 15:3 phantoms have properties similar to COM and brushite, 15:5 ratio possess properties similar to uric acid, while 15:6 has similar properties to struvite stones. Durham, NC© 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e703 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Michael Lipkin More articles by this author Dorit Zilberman More articles by this author Neal Simmons More articles by this author Eric Esch More articles by this author Glenn Preminger More articles by this author Pei Zhong More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

1811 PRELIMINARY EVALUATION OF BIOIMPEDANCE ANALYSIS (BIA) AS A NOVEL PREDICTOR OF EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY (ESWL) SUCCESS

24.7 (9.3-36) 34.9 (27.5-41.7) 0.041 Source of Funding: None ter (15:3-8.2•106Kg/m2s, 15:4-6.4•106Kg/m2s, 15:5-5.2•106Kg/m2s, 15: 6-4.9•106Kg/m2s) with transverse wave speed following a similar trend (15:3-4.6•106Kg/m2s, 15:4-3.5•106Kg/m2s, 15:5-3.1•106Kg/m2s, 15:6- 2.8•106Kg/m2s). CONCLUSIONS: The range of physical properties produced with powder to water ratios of 15:3 to 15:6 matches those of human kidney stones. A stone phantom possessing the physical and acoustic properties similar human kidneys stones can be produced with different BegoStone powder to water ratios: 15:3 phantoms have properties similar to COM and brushite, 15:5 ratio possess properties similar to uric acid, while 15:6 has similar properties to struvite stones.

Infinite periodic model of human lung

As described in a companion abstract, an investigation is underway to develop a bioacoustic model of human lung. In parallel with the numerical model described in the companion abstract, a semianalytic model is being developed. The basic unit cell, a truncated octahedron, is the same. In contrast here, the medium is assumed to be infinite in extent. The resulting lattice possesses cubic symmetry, and, for homogeneous deformation, all material properties are determined by a single unit cell. Deformation of the unit cell is determined by the 24 vertices of the polyhedron, only 6 of which are independent. In this presentation we discuss quasistatic deformation of the discretized medium, and thus ignore inertia and energy dissipation. An analytic model for the nonlinear elasticity of collagen and elastin is used to determine the stiffnesses of the springs connecting vertices of the polyhedra. Minimization of the potential energy for a given macroscopic deformation permits calculation of microscopic deformation within the unit cell, which in turn determines the stresses and therefore the elastic constants. Sample calculations will be presented, including the longitudinal and transverse wave speeds in the medium as functions of direction and orientation. [Work supported by ONR and ARL IR&D.]

Effects of initial stress on transverse wave propagation in carbon nanotubes based onTimoshenko laminated beam models

Based on Timoshenko laminated beam models, this paper investigates the influence ofinitial stress on the vibration and transverse wave propagation in individual multi-wallcarbon nanotubes (MWNTs) under ultrahigh frequency (above 1 THz), in which the initialstress in the MWNTs can occur due to thermal or lattice mismatch between differentmaterials. Considering van der Waals force interaction between two adjacent tubes andeffects of rotary inertia and shear deformation, results show that the initial stress inindividual multi-wall carbon nanotubes not only affects the number of transverse wavespeeds and the magnitude of transverse wave speeds, but also terahertz criticalfrequencies at which the number of wave speeds changes. When the initial stressin individual multi-wall carbon nanotubes is the compressive stress, transversewave speeds decrease and the vibration amplitude ratio of two adjacent tubesincreases. When the initial stress in individual multi-wall carbon nanotubes isthe tensile stress, transverse wave speeds increase and the vibration amplituderatio of two adjacent tubes decreases. The investigation of the effects of initialstress on transverse wave propagation in carbon nanotubes may be used as auseful reference for the application and the design of nanoelectronic and nanodrivedevices, nano-oscillators, and nanosensors, in which carbon nanotubes act as basicelements.

The Use of Chemical Treatments for Improved Comminution of Artificial Stones

The acoustic and mechanical properties of various stone compositions are significantly different and thus result in varying degrees of fragility. Consequently, results to shock wave lithotripsy (SWL) are influenced accordingly. We report the results of a study of fragility of various stone compositions, and the influence on each stone's baseline physical properties and fragility when exposed to various chemolytic solutions. Before SWL artificial stones of differing compositions were irrigated with various chemolytic solutions. Calcium oxalate monohydrate (COM) stones were treated with ethylenediaminetetraacetic acid (EDTA), stones composed of magnesium ammonium phosphate hydrogen were treated with hemiacidrin, and stones made of uric acid (UA) were treated with tromethamine. Synthetic urine served as a control for all stone groups. Using an ultrasound transmission technique, longitudinal wave propagation speed was measured in all groups of artificial stones. Stone density was also measured by using a pycnometer (based on Archimedes' principle). Based on these measurements transverse (shear) wave speed (assuming a constant Poisson's ratio), wave impedance and dynamic mechanical properties of the artificial stones were calculated. Moreover, the microhardness of these artificial stones was measured, and fragility testing using SWL with and without pretreatment with the previously mentioned chemolytic solutions, was performed. Wave speed, wave impedance, dynamic mechanical properties and microhardness of EDTA treated COM stones and tromethamine treated UA stones were found to decrease compared to untreated (synthetic urine) control groups. The suggestion that chemolytic pretreatment increases stone fragility was verified by the finding of increased stone comminution after SWL testing. Combining this medical pretreatment and SWL, the findings demonstrate a significant impact of various solvents on stone comminution, in particular EDTA treated COM stones, tromethamine treated UA stones and hemiacidrin treated magnesium ammonium phosphate hydrogen stones. These data suggest that by altering the chemical environment of the fluid surrounding the stones it is possible to increase the fragility of renal calculi in vitro. These results indicate that appropriate chemical treatments may provide a useful adjunctive modality for improving the efficacy of stone comminution during shock wave lithotripsy.

Timoshenko-beam effects on transverse wave propagation in carbon nanotubes

This paper studies effects of rotary inertia and shear deformation on transverse wave propagation in individual carbon nanotubes (CNTs) within terahertz range. Detailed results are demonstrated for transverse wave speeds of doublewall CNTs, based on Timoshenko-beam model and Euler-beam model, respectively. The present models predict some terahertz critical frequencies at which the number of wave speeds changes. The effects of rotary inertia and shear deformation are negligible and transverse wave propagation can be described satisfactorily by the existing single-Euler-beam model only when the frequency is far below the lowest critical frequency. When the frequency is below but close to the lowest critical frequency, rotary inertia and shear deformation come to significantly affect the wave speed. Furthermore, when the frequency is higher than the lowest critical frequency, more than one wave speed exists and transverse waves of given frequency could propagate at various speeds that are considerably different than the speed predicted by the single-Euler-beam model. In particular, rotary inertia and shear deformation have a significant effect on both the wave speeds and the critical frequencies especially for CNTs of larger radii. Hence, terahertz transverse wave propagation in CNTs should be better modeled by Timoshenko-beam model, instead of Euler-beam model.

Electrodynamics and elasticity

We consider a Lorenz-like gauge theory with a second speed parameter that differs from the speed of light. This theory extends electrodynamics so that it has two speeds corresponding to the speeds of transverse and longitudinal waves in vacuum. The two-parameter extension of electrodynamics can be formally mapped onto the linear theory of elasticity. Because the case of equal speeds is not realized in an elastic medium, a compressible medium cannot model electromagnetism. In the Coulomb gauge electrodynamics can be formally mapped onto incompressible elasticity, which suggests that a linear-elastic incompressible medium can serve as a model of electromagnetism.

REFLECTION OF PLANE WAVES BY THE FREE BOUNDARY OF A POROUS ELASTIC HALF-SPACE

In the present paper, we study reflection of inclined incident plane waves from a free boundary of the half-space in which the material is described by constitutive equations valid for elastic solids with voids. Both the cases of the transverse and longitudinal incident waves are considered, and it is shown that only the transverse one can propagate in the solid without attenuation, after having been reflected from the free boundary surface. The reflection coefficient and the amplitude of the surface oscillations are expressed in explicit form. The general results are demonstrated for several hypothetical porous materials, and it is shown that the reflection coefficient and the vibration amplitude are typically less than in classical media without voids. However, for relatively large transverse wave speed and high porosity, free boundary oscillation can exceed the classical one.

Wave motions in unbounded poroelastic solids infused with compressible fluids

Looking at rational solid-fluid mixture theories in the context of their biomechanical perspectives, this work aims at proposing a two-scale constitutive theory of a poroelastic solid infused with an inviscid compressible fluid. The propagation of steady-state harmonic plane waves in unbounded media is investigated in both cases of unconstrained solid-fluid mixtures and fluid-saturated poroelastic solids. Relevant effects on the resulting characteristic speed of longitudinal and transverse elastic waves, due to the constitutive parameters introduced, are finally highlighted and discussed.

Time resolved plastic deformations in rods subjected to transverse impact

This paper describes experiments to record deformation profiles versus time in metallic rods subjected to transverse ballistic impacts. Rod materials included a tungsten alloy, four alloys of steel, titanium, and copper. The deformation profiles were analyzed to determine time resolved transverse plastic deformation wave speeds in all the rod materials and to estimate effective fracture shear strains in some of the materials. These material parameters are key elements in an analytical model to estimate deformations and failure in long rod penetrators subjected to transverse loads arising from non-ideal plate penetration geometries (yaw and obliquity). The rod materials were also subjected to tensile tests and Taylor anvil impact tests to measure static tensile and dynamic compressive strengths and longitudinal plastic wave speeds. The Taylor anvil and transverse rod impact tests together furnish the required dynamic material properties for comparing the penetration effectiveness of candidate rod materials and geometries.

ACOUSTIC AND MECHANICAL PROPERTIES OF ARTIFICIAL STONES IN COMPARISON TO NATURAL KIDNEY STONES

Standardized and reproducible artificial kidney stone models are important for performing comparative studies of different lithotripsy modalities. The acoustic and mechanical properties of renal calculi dictate the manner by which stones interact with the mechanical stresses produced by shock wave lithotripsy (SWL) or intracorporeal lithotripsy modalities. We have developed a novel artificial kidney stone model that is made of natural substances found in real kidney stones. These stone models appear to be much closer in physical properties to natural kidney stones than previously used stone models. The acoustic and mechanical properties of six groups of artificial stone models were compared to corresponding natural stones of similar compositions. Moreover, three groups of artificial stone models made of plaster-of-Paris were compared to their natural counterparts. In terms of acoustic properties, stone density was measured using a pycnometer based on Archimedes' principle, whereas longitudinal and transverse (or shear) wave propagation speeds were measured using an ultrasound pulse transmission technique. These values were used to calculate wave impedance and dynamic mechanical properties (bulk modulus, Young's modulus, and shear modulus) of the stones. The microhardness of the stones was measured and the effect of composition on stone fragility was evaluated. Artificial stones, when compared to natural stones of similar composition, showed similar trends in longitudinal and transverse wave speeds, wave impedance, and dynamic elastic moduli. However, values for the artificial stones were uniformly low compared to those of natural stones, suggesting that these artificial stones may be more amenable to shock wave fragmentation. The results of SWL on stone fragmentation of artificial and natural stones also revealed similar trends with the exception of artificial cystine stones which were found to be the most resistant to shock wave fragmentation. The results indicate that the physical properties of artificial stones made of natural stone materials are comparable to renal calculi of the same chemical composition. The data suggests that these stone phantoms are suitable for performing standardized and reproducible in vitro investigations, especially with regards to fragility of kidney stones of different chemical compositions during SWL.

Existence and uniqueness of Stoneley waves

SUMMARY The basic existence-uniqueness theory for Stoneley waves propagating along a plane interface between different isotropic elastic media is re-examined, using a matrix formulation of the secular equation. The resulting development is appreciably simpler than previous treatments of the theory. The domain of existence of Stoneley waves and the limiting curves forming its outer boundary are characterized in terms of coordinates β21/β22 and μ2/μ1 where μ1, μ2 are the shear moduli and β1, β2 the speeds of transverse plane waves in the constituent media. The equations of the limiting curves are given explicitly and exemplified numerically.

49873 Numerical simulation of the instabilities associated to the recovery of elastic constants of anisotropic solids from quasi-longitudinal velocities alone : Castagnede, B.; Every, A.G.; Sachse, W. Comptes Rendus de R'Academie des Sciences, Series II, vol. 314, no. 9, pp. 865–871 (23 Apr. 1992)

The present Note describes instabilities observed in the use of numerical simulations for recovering the elastic constants of anisotropic solids when only bulk quasi-longitudinal (qL) velocities are taken into account. Both 2-D and 3-D versions of the simulation are discussed, and a number of numerical examples are presented. The influence of the angular range of the data, the density of the simulated data, as well as the addition of a few transverse wavespeeds are discussed in some detail. Some practical implications related to laser generation experiments are pointed out.