Propagation Velocity Of Elastic Waves Research Articles

Modelling the poroelasticity of rocks and ice

For many geophysical and astrophysical applications the relationship between physical bulk properties and porosity is needed. As part of the preparation for the ‘Rosetta’ comet rendezvous mission, a simple model for the porosity dependence of the elastic properties of granular media, i.e. the elastic moduli and the propagation velocities of elastic waves, has been developed based on textural properties and the contact stiffness of the constituent particles. It is shown that the derived relationships fit very well with sandstone data. The model is also consistent with data for snow and ice and is in agreement with the transformation mechanisms from snow to ice. A short review shows the relevance to another physical bulk property, the thermal conductivity.

Physical properties and phase transitions of bis(guanidinium)zirconium bis(nitrilotriacetate)hydrate, [C(NH2)3]2Zr[N(CH2COO)3]2· H2O

AbstractLarge single crystals of optical quality of bis(guanidinium)zirconium bis(nitrilotriacetate)hydrate have been grown from aqueous solutions. Complete elastic, thermoelastic and piezoelastic tensors have been determined by ultrasonic methods. In addition, the tensor of thermal expansion, refractive indices, dielectric and piezoelectric constants have been studied in the range between 210 K and 330 K. Most physical properties investigated show a strong anisotropy. The piezoelectric constantd123exceedsd111ofα-quartz by a factor of 25. Two higher-order phase transitions appear at about 287 K and 290 K. The intermediate phase exhibits strong anomalies of the temperature and pressure dependence of the propagation velocities of quasi-longitudinal elastic waves having a large component of the displacement vector parallel to [010].

Elastic wave propagation velocity in estimating the mechanical properties of bone in elderly women

Elastic wave propagation velocity in estimating the mechanical properties of bone in elderly women

Some static and vibrational properties of aluminium by a local pseudopotential

The pseudopotential investigation of various properties of aluminium is studied in terms of the real-space sum of Born-von Karman central-force constants. A simple local model potential depending on a single parameter has been used to investigate the ion-ion interaction, interatomic force constants, dynamical elastic constants, bulk modulus, deviation from Cauchy relation, Poisson's ratio, Young's modulus, propagation velocity of elastic waves, phonon dispersion curves and degree of elastic anisotropy. The effect of exchange and correlation on conduction electrons is also considered separately by using various forms of the dielectric (screening) functions. Overall good agreement with the available theoretical and experimental data is achieved in the present work.

Evaluation of the influence of various parameters on the velocity of elastic wave propagation in a rock medium : Bala, M Trans Porous MediaV9, N1/2, Oct 1992, P123–134

Evaluation of the influence of various parameters on the velocity of elastic wave propagation in a rock medium : Bala, M Trans Porous MediaV9, N1/2, Oct 1992, P123–134

The evaluation of the influence of various parameters on the velocity of elastic wave propagation in a rock medium

A full waveform recording in a borehole during acoustic logging makes it possible to determine the elastic parameters of a medium under in-situ conditions.

AN ANALYTICAL RAYPATH APPROACH TO THE REFRACTION WAVEFRONT METHOD1

AbstractSeismic refraction surveying is still an important tool for determining the geometries and elastic wave propagation velocities of near‐surface layers. Many analytical and graphical methods have been developed over the years for refraction interpretation, and these can be classified into two basic groups. The first group visualizes critically refracted rays converging on a common surface position, while the second group, which includes the wavefront methods, makes use of the critical rays emerging from a common point on the refractor.The method described in this paper is an analytical approach to the wavefront methods. The reverse refracted ray received by a geophone is intersected by the forward refracted rays received by subsequent geophones and a common critical refraction point on the refractor is estimated after a series of comparisons. This process is repeated for each geophone to yield the geometry and the velocity of the refractor. Several interpolations are performed to achieve a better accuracy.Palmer's models are used to test the efficiency of the algorithm. The results are presented together with those of other methods applied to the same models.

The elastic behaviour of indium under pressure and with temperature up to the melting point

Abstract The ultrasonic pulse-echo overlap technique has been used to measure pressure and temperature dependences of elastic wave propagation velocities along various crystallographic directions in single-crystal indium. The results provide a complete set of the pressure derivatives of the elastic constants of indium between room temperature and the melting point (429·7 K). This in turn has allowed the long-wavelength acoustic mode Gruneisen parameters to be determined over that temperature range. The values obtained for acoustic mode Gruneisen parameters show that there is a significant increase in vibrational anharmonicity as the melting temperature is approached. To allow determination of the thermal Gruneisen parameters γth up to the melting point, the thermal expansion tensor components α11 and α33 have also been measured. The mean zone-centre acoustic mode Gruneisen parameter γe1 is found to be larger than γth owing mainly to the contributions from the more anharmonic slow shear modes (k[110], e[11...

Propagation velocities of elastic waves in saturated soils

Based on the wave equations established by the authors, the characteristics of propagation velocities of elastic waves in saturated soils are analyzed and verified by ultrasonic test in laboratory and seismic survey in the field. The results provide theoretical basis for the determination of physical and mechanical parameters of saturated soils using propagation velocities of elastic waves, especially P-wave Velocity.

Anomalies in elastic properties and features of electronic transitions in lanthanum and praseodymium at pressures up to 84 kbar

The propagation velocities of longitudinal and transverse elastic waves in polycrystalline praseodymium have been measured by a pulsed ultrasound method at pressures up to 84 kbar at room temperature. The density, elastic constants, and Debye temperature are calculated as functions of pressure. The anomalies found in the pressure dependence of the sound velocities in praseodymium, as in lanthanum, which was studied previously, reflect an additional anharmonicity of longitudinal and transverse acoustic phonons at two phase transitions which occur in the intervals 12–50 and 66–80 kbar. The experimental results on lanthanum and praseodymium are discussed on the basis of a pseudopotential method and in the Friedel model with 6s-5d electronic transitions. Estimates show that the observed anomalies in the elastic characteristics of both of these metals are caused by an accelerated 6s-5d “flow” of electrons. Similar anomalies should be observed in caesium II near the first-order isomorphic electronic 6s-5d transition at 42.2 kbar.

Nonlinear piezoelectricity and electrostriction of alpha quartz

Starting from the rotationally invariant nonlinear equations of electroelasticity the initial derivative of the propagation velocity of elastic waves with respect to the magnitude of an electric biasing field is derived. This derivative is given by an expression which is linear in third-order material constants. From propagation measurements of ultrasonic waves under the application of a constant electric field, values for the eight independent components of the nonlinear piezoelectric tensor eKABCD and for the eight independent components of the electrostriction tensor lKLAB for alpha quartz are obtained. While some of the electrostriction constants remain rather uncertain, the nonlinear piezoelectric constants are determined with good accuracy.

Energy Propagation Velocity of Elastic Waves in Sandwich Layer

The explicit characteristic velocities of mechanical energy are obtained in computation for designing structures and acoustical inspections of a sandwich composite plate made of three elastic constituent layers. The dependence of the energy velocity upon the parameters such as ratio of shear velocity, volume fraction, and Poisson’s ratios of constituent layers is discussed in graph form with curves of frequency to energy arrival time. Numerical calculations are carried out up to several higher modes within the range of practical frequencies. The results show that the second mode energy velocity is strongly dependent on the ratio of shear velocity of each constituent layers.

Computerized calculation of elasticity moduli of anisotropic rocks

Study of the physical properties of rocks, including elasticity, is essential for the mining of minerals. Dynamic methods of investigation, especially ultrasound pulse probing of specimens, are co-,,only used to study rock elasticity. For determination of the elastic characteristics of an isotropic rock, it is sufficient to measure the propagation velocity of longitudinal and transverse elastic waves in one arbitrary direction. Many rocks, however, display anisotropy of elastic properties, that is, their elastic properties differ depending on the direction in the rock. The elastic properties of the rock in that case are described by Hooke's law for anisotropic media,

An ordering principle for elastic wave propagation velocities

An elastic solid has, in general, three distinct wave propagation velocities in a given direction. According to a theorem of Fedorov, however, there are only two distinct velocities of propagation associated with an axis of material symmetry greater than binary symmetry. The converse of this theorem is proved herein, namely, that it is only in directions of material symmetry greater than binary symmetry that two distinct velocities occur. This leads to an ordering principle for elastic wave propagation velocities, that is, that the order of the velocities, regarded as functions of the direction of propagation, is invariant.

Seismic methods for study of soil building properties

Information about distribution of elastic wave propagation velocities Vp, Vs in the subsurface zone of a soil mass can be obtained rapidly and cheaply by means of special seismic methods. With the help of these methods it is possible to study the elastic properties in detail in a soil mass of high structural complexity beginning from depths of 0.01 m. Correlative relations may be used to determine the distribution of deformation-strength characteristics of soils both in the area of the mass and at depth. By means of measurements made during construction it is possible to correct the placement of fill in dams, artificial foundations, roads, etc.

Three Dimensional Representation of Texture and Anisotropies of Mechanical Properties in Cold Rolled Mild Steel Sheet

The present experiment has been made with two purposes.One is to make a precise analysis of textures of cold rolled and recrystallized mild steel sheets by means of a three-dimensional orientation distribution function (ODF). The materials used, are aluminium killed steel sheets and rimmed steel sheets.The other is to find a quantitative relationship between the anisotropy of mechanical properties of those sheets and the textures represented by the ODF. Young's modulus, Lankford value and propagation velocities of elastic waves are chosen as the mechanical properties and they are related to the ODF by the method proposed in this study.For the texture analysis, the development of the recrystallized textures is reasoned systematically. The preferred orientations in the recrystallized texture are also made clear by the ODF. The calculated values of the mechanical properties are all in good agreement with the experimentally obtained ones, that is, of Young's modules, Lankford value and the propagation velocity. The square of the propagation velocity is also correlated with the averaged Lankford value as theoretically predicted.

Effect of physical properties of peat deposits on the velocity of elastic wave propagation in them (in Russian) : Kmitovenko, A T; Aleksandrov, B M; Zelenskii, I I Russia: Minist Vyssh Sredn Spets Obrazov, Izv VUZ Gorn Zh, N12, 197, P16–19

Effect of physical properties of peat deposits on the velocity of elastic wave propagation in them (in Russian) : Kmitovenko, A T; Aleksandrov, B M; Zelenskii, I I Russia: Minist Vyssh Sredn Spets Obrazov, Izv VUZ Gorn Zh, N12, 197, P16–19

Propagation of ultrasonics in bones

The possibility has been established of determining the propagation velocity of elastic waves in bones by an ultrasonic technique in order to study the healing of fracture. An experimental apparatus of new design is described, which has been developed and made for research purposes and diagnostic measurements. The apparatus enables a numerical evaluation of the propagation velocity of ultrasonics in a bone to be automatically portrayed on the counter display, and the complete wave pattern or its details to be watched on the oscilloscope screen. The trends and principles of the exploratory measurements and practical diagnostics are discussed and, after statistical processing, certain results from our determinations are also quoted.

Use of elastic wave propagation velocities to study the three-dimensional geometry of jointing

Use of elastic wave propagation velocities to study the three-dimensional geometry of jointing

Travel-time curves of reflected waves interpreted on principle of conjugate points

Velocities distribution in the overburden and coordinates of the reflecting plane are shown to be simultaneously obtainable in principle, even if the propagation velocities of elastic waves are not known. Travel-time curves for two different points of the excitation, both of which represent the same part of the reflecting plane, are sufficient for a definite solution of this problem. Its exact solution is possible, in case the propagation velocity in the overburden is constant, under certain conditions. -- V.P. Sokoloff.