A method for computing the transient radiation from a wide circular source, acting at a solid surface, is given for two different normal force apodizations. This method, based on a double Laplace–Hankel transform and a Cagniard inversion, allows an exact formulation of the impulse response to be obtained for two components of the displacement at any point inside the solid and is amenable to computing the field for an arbitrary time excitation. Numerical results are presented and are compared with experimental results for generation by a piezoelectric transducer.
A method for computing the radiation from a thermal expansion source, generated at a solid surface by a laser pulse of finite width, is evaluated for two radial beam energy distributions. A theoretical expression for the impulse response is obtained for two components of the displacement at any point within the solid, and may be used to compute the field for an arbitrary time excitation. Numerical results are presented, and are compared to experimental results for generation by a pulsed laser.
It is well established that the field from uniformly vibrating piston transducers may be considered as being derived from two components: a plane wave and an edge wave. These have been both predicted and observed in practice, but it would seem that a mathematical expression for the edge-wave component has not yet been developed fully. In this article, expressions are developed for the pressure and particle velocity edge waves that can be used to calculate the field that results when a plane wave is diffracted by an edge. The expressions are used to study a particular example, namely, that of an arbitrarily shaped piston radiator. The results for certain situations are shown to agree with existing solutions for a disk source.
Illumination of a specimen by a pulsed focused laser is known to induce elastic waves, and models are available for both cases of thermoelastic generation and liquid evaporation. In this article, the inverse problem of recovering the elastic constants of a specimen from experimental waveforms recorded on- and off-epicenter is considered. An algorithm, based on nonlinear least-squares fitting, is presented and has been used on experimental displacement signals recorded on an aluminum plate with a Michelson interferometer. The choice of the receiver position is discussed and experimental results are given.
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