Showing papers on "Lamb waves published in 1975"
Book•
01 Jan 1975
TL;DR: In this article, a comprehensive study of elastic wave propagation in solids is presented, ranging from the theory of waves and vibrations in strings to the three-dimensional theory of elastic waves in thick plates.
Abstract: The book presents a comprehensive study of elastic wave propagation in solids. Topics covered range from the theory of waves and vibrations in strings to the three-dimensional theory of waves in thick plates. The subject is covered in the following chapters: (1) waves and vibrations in strings, (2) longitudinal waves in thin rods, (3) flexural waves in thin rods, (4) waves in membranes, thin plates and shells, (5) waves in infinite media, (6) waves in semi-infinite media, (7) scattering and diffraction of elastic waves, and (8) wave propagation in plates and rods. Appendices contain introductory information on elasticity, transforms and experimental techniques. /TRRL/
3,359 citations
TL;DR: In this article, the boundary conditions for the discrete wave equation are constructed using projection operators, and the separation of waves into ingoing and outgoing waves inherent in these boundary conditions greatly facilitates diagnostics.
354 citations
TL;DR: In this paper, a discussion of the modes of the first class, as well as of the Rayleigh mode, is presented, and the sheet structure of the elastic surface waves is discussed in an appendix.
Abstract: Various surface wave modes may exist on solid elastic cylinders imbedded in a fluid. They fall into two classes, having velocities close to either the wave speed in the fluid (Stoneley‐ and Franz‐type modes), or to the bulk wave speeds in the solid (Rayleigh‐ and Whispering Gallery‐type modes). Using analytic and numerical methods, we present here a discussion of the modes of the first class, as well as of the Rayleigh mode. In the limit of infinite cylinder radius, the wavenumbers of the Rayleigh and Stoneley modes tend towards those of the Rayleigh and Stoneley waves on a flat elastic half‐space, while the Franz‐mode wavenumbers tend towards the wavenumber of sound in the ambient fluid. The sheet structure of the elastic surface waves is discussed in an appendix.Subject Classification: 35.54; 40.26;30.50;20.35.
69 citations
TL;DR: A relation connecting the reflexion and transmission coefficients for scattering of water waves by a fixed body with the far-field radiated waves due to forced motions of the same body is derived in this article.
Abstract: A relation connecting the reflexion and transmission coefficients for scattering of water waves by a fixed body with the far-field radiated waves due to forced motions of the same body is derived Two alternative derivations are given, including a simple argument based on the analysis of an appropriate linear superposition of the two problems, and a more formal application of Green's theorem to the two potentials For bodies with horizontal symmetry, the transmission and reflexion coefficients are related to the phase angles of the far-field radiated waves associated with symmetric and antisymmetric forced motions of the body Some general conclusions follow for arbitrary symmetric bodies, and these are verified in specific cases by comparison with existing solutions The applicability of these relations to other types of wave problem is noted
37 citations
TL;DR: In this article, the equations governing Rayleigh and Lamb mode propagation for free and liquid-loaded solids are examined for both free and non-free solids, and examples are given to show under what conditions the free-solid approach yields acceptable solutions for the velocities.
32 citations
TL;DR: In this article, two types of bulk wave are excited by an incident Rayleigh wave at a groove discontinuity and their propagation and power characteristics are investigated, where mode-conversion problem is treated by a boundary perturbation technique.
Abstract: Characteristics of bulk waves generated by an incident Rayleigh wave at a groove discontinuity are studied in this paper. The groove, etched on top of a semi−infinite elastic substrate, is an elementary building block of a reflector−array type of signal processing devices. The mode−conversion problem is treated by a boundary perturbation technique. Two types of bulk wave are excited, i.e., p and sv waves. Their propagation and power characteristics are investigated.
28 citations
01 Jan 1975
TL;DR: In this article, the characteristics of attenuation and scattering processes are examined and a description is given of shock waves and impact problems in composites, and a number of experiments are also reported.
Abstract: Anisotropic waves in composites are considered, taking into account wave speeds, wave surfaces, flexural waves in orthotropic plates, surface waves, edge waves in plates, and waves in coupled composite plates. Aspects of dispersion in composites are discussed, giving attention to pulse propagation and dispersion, dispersion in rods and plates, dispersion in a layered composite, combined material and structural dispersion, continuum theories for composites, and variational methods for periodic composites. The characteristics of attenuation and scattering processes are examined and a description is given of shock waves and impact problems in composites. A number of experiments are also reported.
25 citations
21 citations
TL;DR: In this article, the connection between creeping wave and flat surface wave theory was established by investigating the limit of acoustic scattering from a solid elastic cylinder imbedded in a fluid, as its radius tends to infinity.
Abstract: The connection between creeping wave and flat surface wave theory is established by investigating the limit of acoustic scattering from a solid elastic cylinder imbedded in a fluid, as its radius tends to infinity. After applying the Watson‐Sommerfeld transformation to the scattering solution, it is shown analytically that the asymptotic expressions for the residue terms (creeping waves) in the Whispering Gallery mode series combine to form separately both the longitudinal and the transverse lateral waves on a flat surface. The cylindrical Rayleigh wave tends individually towards the flat Rayleigh wave, while the Franz and Stoneley waves disappear.
20 citations
TL;DR: In this paper, a series of simulated acoustic emission experiments in thin plates and bars were conducted to assess the effects of structural geometry on the detection of emission, and it was shown that the structure introduces peaks in the received signal spectra corresponding to thickness resonances that may be estimated from Lamb wave theory.
Abstract: A series of simulated acoustic emission experiments in thin plates and bars conducted to assess the effects of structural geometry on the detection of emission is described. It is shown that the structure introduces peaks in the received signal spectra corresponding to thickness resonances that may be estimated from Lamb wave theory. Spectra of acoustic emission signals from a thin−walled pressure vessel show a peak at the frequency corresponding to the lowest symmetric plate mode. It is concluded that a significant portion of the energy detected by a surface contact transducer on a thin−walled structure is concentrated at these resonances and should be accounted for in choosing a detection system.Subject Classification: 35.10, 35.80.
19 citations
TL;DR: In this article, a simple method of reducing the amplitude of Lamb waves in primitive equation model forecasts has been proposed and tested, which makes use of a Boussinesq-type approximation in which the vertical mean mass divergence is set equal to zero.
Abstract: A simple method of reducing the amplitude of Lamb waves in primitive equation model forecasts has been proposed and tested. This method makes use of a Boussinesq-type approximation in which the vertical mean mass divergence is set equal to zero. It effectively reduces the Lamb waves by a factor of 3 in the example shown here and does not degrade the forecast accuracy. The largest reduction in Lamb wave amplitude is found in the tropical regions.
TL;DR: In this article, it was shown that for thermal radiation conditions at the boundary, pure compressional and flexural modes of motion cannot exist in a traction-free plate, and that the modes become uncoupled only for the special cases of isothermal and adiabatic boundary conditions.
Abstract: It is shown within the framework of the linear theory of thermoelasticity that, for thermal radiation conditions at the boundary, pure compressional and flexural modes of motion cannot exist in a traction-free plate. Rigorously, the modes become uncoupled only for the special cases of isothermal and adiabatic boundary conditions: approximately, however, they are uncoupled even in the general case if the analysis is confined to the lowest-order terms in the small dimensionless frequency associated with such problems. Then the motions represent generalizations of the classical Rayleigh-Lamb waves. The effect of thermal conductivity is to reduce the phase velocity and introduce disipation, and is noticeable primarily for long waves.
TL;DR: In this article, the nonlinear behavior of plasma due to resonant three-wave interactions is considered, both as a decay instability arising from a single pump wave and as resonant mixing when two waves are initially present in the plasma.
Abstract: Nonlinear behaviour of plasma due to resonant three-wave interactions is considered, both as a decay instability arising from a single pump wave and as resonant mixing when two waves are initially present in the plasma Observations of both processes involving longitudinal electron (Langmuir) waves and ion waves are reported and quantitative measurements given The interaction between coherent waves is related to that between random-phase waves and in this way the cross-section for plasmon-plasmon interaction derived In a finite plasma, resonant three-wave interactions in which all waves are Langmuir waves are possible and quantitative results for this process are given The new results of this paper and an earlier one are summarized and combined in relation to the dispersion diagram of Langmuir waves
TL;DR: In this paper, a system of equations describing wave propagation in fluid-filled elastic tubes is examined with a view to achieving its reduction to a canonical form associated with the conventional wave equation.
Abstract: A system of equations descriptive of wave propagation in fluid-filled elastic tubes is examined with a view to achieving its reduction to a canonical form associated with the conventional wave equation. Two specific solutions are displayed and these are then used to consider a specific boundary value problem.
TL;DR: In this article, an analysis of the non-linear propagation of longitudinal waves along a bar whose geometrical and material properties vary slowly along its length, taking into account the effects of a small viscosity, is presented.
TL;DR: In this paper, the elastic constants c11,c12 and c44 of sodium bromate have been calculated from measurements of the velocities of 10 MHz ultrasonic waves transmitted through a single crystal specimen in the following directions: longitudinal waves transmitted in the (100) and (111) directions, and shear waves transmitted from the ( 111) direction.
Abstract: The elastic constants c11,c12 and c44 of sodium bromate have been calculated from measurements of the velocities of 10 MHz ultrasonic waves transmitted through a single crystal specimen in the following directions: longitudinal waves transmitted in the (100) and (111) directions, and shear waves transmitted in the (111) direction. The measurements have been made over the range 150-300K. The results have been extrapolated to 0K to permit the calculation of the Debye characteristic temperature which at 0K was found to be 238K.
Journal Article•
TL;DR: An effective and practical Lamb wave inspection system has been developed by Reynolds Metals Research to inspect aluminum sheet in gages from 0.25 mm (0.010 in.) to 3.20 mm(0.125 in.). Utilizing this system, an ultrasonic number is derived which relates the Lamb wave indication in the sheet to the final product quality.
Abstract: An effective and practical Lamb wave inspection system has been developed by Reynolds Metals Research to inspect aluminum sheet in gages from 0.25 mm (0.010 in.) to 3.20 mm (0.125 in.). Utilizing this system, an ultrasonic number is derived which relates the Lamb wave indication in the sheet to the final product quality. This ultrasonic number can readily be computed for each Lamb wave indication. Surface defects, small internal discontinuities and inclusions are detected by performing an inspection at frequencies from 12 to 15 MHz. 100%, of the volume of a sheet sample (e.g., 0.50 m (20 in.) wide by 1.2 m (48 in.) long by 0.43 mm (0.017 in.) thick) can be inspected in one traverse of the sheet width. When this is completed, the sheet material, if on a continuous coil is indexed to the next inspection position. An application of this technique to aluminum can stock will be described. Twenty-nine coils of can stock were sampled in our laboratory. 770 Lamb wave indications (presumed to be discontinuities) were selected for study. An ultrasonic number for each was computed. A can blank was obtained from the sheet in such a way that when the can was formed, the Lamb wave-detected discontinuity would occur in a known critical area of the final product. The 770 Lamb wave indications yielded ultrasonic numbers ranging from 1.6 to 38.5. Our study shows that, depending on the confidence level needed, a specific ultrasonic number can be used for determining a "go-no go" test when inspecting sheet material. For example, we have found that for ultrasonic numbers greater than or equal to 10,71% of the can blanks produced critical defects in the final product. As we increase or decrease this number, generally the percent critical defects increases or decreases, respectively. Equipment and procedures currently are being developed for plant installation. /Author/
TL;DR: In this article, the properties of wave normal surfaces in a stratified, conducting atmosphere under the influence of an applied magnetic field were investigated, where acoustic-gravity and magneto-gravity waves were compared.
Abstract: We consider the properties of waves in a stratified, conducting atmosphere under the influence of an applied magnetic field. Wave normal surfaces are exhibited for acoustic-gravity and magneto-gravity waves, and the propagation of these modes is compared. (AIP)
01 Jan 1975
TL;DR: In this article, the potential of the reflected wave is in phase with that of the incident wave, but the plate absorbs the incident waves when it is biased at a large positive potential.
Abstract: Reflection and absorption of electron plasma waves are studied experimentally in a Q-machine. The waves are reflected from a cold, negatively biased metal plate. The potential of the reflected wave is in phase with that of the incident wave, but the plate absorbs the incident waves when it is biased at a large positive potential. On the other hand, an ionizing hot plate reflects the waves and a phase reversal is observed. A conical target can be used as a wave absorber under some experimental condition.
TL;DR: In this article, the dispersion curves of free waves in free plates were investigated, and it was shown that for certain conditions a simple exact solution is possible, since incident shear (SV) waves are decoupled from the transmitted longitudinal (P) wave (and vice versa).
Abstract: We have investigated the dispersion curves of free waves in free plates. We have shown that for certain conditions a simple exact solution is possible, since incident shear (SV) waves are decoupled from the transmitted longitudinal (P) wave (and vice versa). The concept of phase decoupling yields a useful description for the construction of approximate dispersion curves in terms of certain decoupled modes M1−M4. The validity of various approximations based on these modes is discussed. The fomulation may be readily extended to anisotropic and to active plates.Subject Classification: 40.24.
TL;DR: In this article, it was shown that Rayleigh waves can be generated and received by the electro-acoustic method, and that the conversion factor is sufficient for the technique to find application in low power ultrasonics.
Abstract: It is shown that Rayleigh waves can be generated and received by the electro-acoustic method. The conversion factor is sufficient for the technique to find application in low power ultrasonics.
TL;DR: In this article, a class of exact solutions for a coupled set of nonlinear equations describing the interaction between two propagating waves and a system of particles is found, which include traveling wave solutions of the non-linear coupled equations.