Showing papers on "Lamb waves published in 1979"
510 citations
TL;DR: In this article, it is shown that the L(0, 1) mode, which is comparable to the A0 Lamb wave mode in flat plate, can be generated with acceptable efficiency.
309 citations
TL;DR: In this article, a new electromagnetic transducer configuration was described for generating horizontally polarized shear (SH) waves in ferromagnetic materials, which consists of a meander coil and static bias magnetic field parallel to the coil elements.
Abstract: A new electromagnetic transducer configuration is described for generating horizontally polarized shear (SH) waves in ferromagnetic materials. The transducer consists of a meander coil and static bias magnetic field parallel to the coil elements. This configuration generates no ultrasonic waves in a nonmagnetic metal since the induced eddy currents are parallel to the bias field and the driving Lorentz forces vanish. However, the configuration provides coupling to SH waves in ferromagnetic materials through magnetostrictive effects. Experimental measurements of the variation of transduction efficiency with bias field in nickel and 4130 steel plate are presented and compared to the efficiency obtained with the same meander coils when the bias is rotated 90° in the plane of the plate so that antisymmetric Lamb waves are generated. Peak efficiencies occur at considerably different bias fields for the two configurations. This result, as well as other features in the data, are interpreted in terms of a simple ...
113 citations
TL;DR: In this paper, the theory of elastic surface waves in a crystalline medium on surface motions of a pre-stressed elastic body is examined and the main results are a general uniqueness theorem and the notion of a neutral set, bounding the domain of existence of surface waves and interpretable as the totality of standing wave solutions.
Abstract: The bearing of the Barnett–Lothe formulation of the theory of elastic surface waves in a crystalline medium on surface motions of a pre-stressed elastic body is examined in this paper. The main results are a general uniqueness theorem and the notion of a neutral set, bounding the domain of existence of surface waves and interpretable as the totality of standing wave solutions. As an application of these ideas a full account is given of the existence of surface waves in a homogeneously deformed elastic body possessing a restricted form of the Hadamard strain-energy function. In conclusion, the difficulties involved in treating an analysis of surface waves as a test of the stability of a loaded semi-infinite elastic body are briefly discussed.
55 citations
TL;DR: In this paper, the effect of negative ions on ion-acoustic waves in plasmas consisting of either a warm or cold ion species was studied and the reflection phenomenon of ions in these waves was also studied.
Abstract: The present investigation of ion-acoustic waves is based on the study of the nonlinearity of plasma waves in a dispersive medium. Here the authors study ion-acoustic solitary waves in a warm ion plasma with non-isothermal electrons and then the results for solitary waves in a plasma with isothermal electrons are obtained. Incorporating the previous results obtained from the solitary wave solutions, the authors generalize the effect of negative ions on ion-acoustic waves in plasmas consisting of either a warm or cold ion species. A reflection phenomenon of ions in these waves is also studied. These results can be generalized, but the discussion is limited to a particular model of the plasma.
54 citations
TL;DR: In this paper, a coupled pair of nonlinear Schrodinger equations for the Langmuir waves and the dispersive ion acoustic wave has been derived for all values of the wave number k l of the low-frequency waves.
54 citations
49 citations
TL;DR: In this article, the integral properties of plane periodic deep-water waves of amplitudes up to the steepest are tabulated by Longuet-Higgins (1975), which are used to define an averaged Lagrangian which, following Whitham, is used to describe the properties of slowly varying wave trains.
Abstract: Accurate integral properties of plane periodic deep-water waves of amplitudes up to the steepest are tabulated by Longuet-Higgins (1975). These are used to define an averaged Lagrangian which, following Whitham, is used to describe the properties of slowly varying wave trains. Two examples of waves on large-scale currents are examined in detail. One flow is that of a shearing current, V ( x ) j , which causes waves to be refracted. The other flow, U ( x ) i , varies in the direction of wave propagation and causes waves to either steepen or become more gentle. Some surprising features are found.
48 citations
TL;DR: In this article, the Christoffel elastic equations are solved for long-wavelength elastic waves of arbitrary direction in cubic crystals, and exact explicit closed expressions are obtained for the phase and group velocities and displacement amplitudes.
Abstract: The Christoffel elastic equations are solved for long-wavelength elastic waves of arbitrary direction in cubic crystals, and exact explicit closed expressions are obtained for the phase and group velocities and displacement amplitudes. The velocity expressions that hold in the special directions are shown to follow from the general result. The problem of determining the elastic constants from the phase velocities in a general crystallographic direction is discussed with particular reference to Brillouin scattering.
42 citations
TL;DR: Using the scattering matrix approach to elastic wave scattering, numerical results are presented for the scattering of P and S waves from prolate and oblate spheroidal cavities and inclusions embedded in an elastic solid for a wide range of wavelengths as discussed by the authors.
Abstract: Using the scattering matrix approach to elastic wave scattering, numerical results are presented for the scattering of P and S waves from prolate and oblate spheroidal cavities and inclusions embedded in an elastic solid for a wide range of wavelengths. The incident waves are plane harmonic waves incident obliquely to the axis of revolution of the spheroid.
01 Aug 1979
TL;DR: In this paper, a new type of Lamb wave device for acoustic focusing is presented, which has an interdigital transducer deposited on a thin piezoelectric ceramic plate.
Abstract: A new type of Lamb wave device for acoustic focusing is presented. The device has an interdigital transducer deposited on a thin piezoelectric ceramic plate. In the device, Lamb wave is radiated from the surface without the interdigital electrodes into water and interferes constructively at a focal point in water.
Patent•
11 Oct 1979TL;DR: The rate of decay of oscillations caused by application of driving pulses to the spaced crystals of an acoustic electric transducer that are mounted on a base is increased by making the thickness of the shield in contact with the ends of the crystals remote from the base such that asymmetrical Lamb waves flowing along the shield that can induce crystal oscillations in the thickness mode have a wavelength equal to twice the spacing between crystals so that their integrated effect is nearly zero as discussed by the authors.
Abstract: The rate of decay of oscillations caused by application of driving pulses to the spaced crystals of an acoustic electric transducer that are mounted on a base is increased by making the thickness of the shield in contact with the ends of the crystals remote from the base such that asymmetrical Lamb waves flowing along the shield that can induce crystal oscillations in the thickness mode have a wavelength equal to twice the spacing between crystals so that their integrated effect is nearly zero.
TL;DR: In this article, an elastic wave transmitting system consisting of an input section with constant impedance, a joint with variable impedance, and an output section having constant impedance is considered, and the following optimization problem is solved for two sample cases: given the properties of the wave transmission system and a limited duration of the incident wave, determine the shape of this wave such that the energy transmission is maximized.
TL;DR: In this article, the effects of Rayleigh waves to those of vertical shear waves on the dynamic response of a variety of realistic soil deposits were compared using a modified version of the Thomson-Haskell-Harkrider method, and the variation with depth of horizontal displacements and shear stresses resulting from the passage of the two types of waves was determined.
Abstract: The main thrust of this paper is to compare the effects of Rayleigh waves to those of vertical shear waves on the dynamic response of a variety of realistic soil deposits. Using a modified version of the Thomson-Haskell-Harkrider method, the variation with depth of horizontal displacements and shear stresses resulting from the passage of the two types of waves is determined. Comparisons of their effects indicate that R- and S-waves produce similar attenuations with depth of horizontal motions, for periods close to or greater than the first natural period of the deposit in vertical shear waves, while the discrepancies observed at much shorter perids are of little practical significance since for typical soil profiles Rayleigh waves of such periods carry only a small portion of the total wave energy. However, the two waves may yield different distributions of shear stresses with depth and induce different motions of the soil particles.
TL;DR: In this article, two additional criteria for the existence of cusp points on elastic wave surfaces are developed, which are plausibly adapted to provide a simple inequality applicable to any section of slowness surface represented by separable quadratic and quartic equations.
Abstract: Two additional criteria for the existence of cusp points on elastic wave surfaces are developed. A previously published method [1] is extended to give a simple necessary and sufficient condition for cusps about (1, 1, 0) axes in cubic and tetragonal media. This criterion is plausibly adapted to provide a simple inequality applicable to any section of slowness surface represented by separable quadratic and quartic equations. Two tables of numerical examples are presented.
01 Jan 1979
TL;DR: A brief overview of shallow bulk acoustic wave generation, propagation, and properties is presented in this article, where the effect is manifested in doubly rotated crystal plates, and certain features of device performance may be inferred from pre-existing calculations for bulk wave plates.
Abstract: A brief overview of shallow bulk acoustic wave generation, propagation, and properties is presented. It is shown how the effect is manifested in doubly rotated crystal plates, and how certain features of device performance may be inferred from pre-existing calculations for bulk wave plates.
TL;DR: In this article, the nonlinear interaction between bulk acoustic waves at a surface to produce surface acoustic waves is analyzed theoretically and the boundary conditions are rigorously satisfied by the total acoustic fields.
Abstract: The nonlinear interaction between bulk acoustic waves at a surface to produce surface acoustic waves is analyzed theoretically. In this analysis both the nonlinear wave equation and boundary conditions are rigorously satisfied by the total acoustic fields. Shear‐wave incidence is treated in detail for isotropic fused quartz and numerical cross sections are evaluated for different angles of incidence. Maximum surface‐wave generation is predicted for geometries corresponding to bulk waves, shear or longitudinal, traveling parallel to the surface.
TL;DR: In this paper, transient wave propagation in elastic homogeneous and isotropic plates, in terms of displacement discontinuities of all order ⩾ 1 at the wave front, is dealt with.
TL;DR: In this article, the free energy of the material, that is, the potential of stresses, is derived by continuum approximations of a microscopic model, and the physical meaning of various contributions in the free energies is discussed.