SummaryIn the passage of elastic waves through a cylindrical rod, phenomena are exhibited that closely resemble those occurring in an electromagnetic waveguide. Following a discussion of the classical Pochhammer-Chree theory for an infinite cylinder, elastic wave propagation in a finite rod is considered under conditions ~hen the rod may be regarded as analogous to an electrical transmission line. In the case of a resonant system, normal mode analysis provides a simplified treatment and it is shown that the results are in agreement with transmission-line theory. A brief discussion is given regarding the identity of the pulse response of a system and its response to continuous waves.
SummaryThe theory governing the excitation of a linear mechanical system by a delta function impulse is summarized. In the case of a finite elastic rod excited by an impulse, the Fourier transform of the output function enables the frequency spectrum of the rod to be obtained. A spectrometer for accomplishing this operation is described and a comparative study is made between the impulse and resonance responses of a cylindrical rod.A discussion of the basic relationships involved in computing the dynamic elastic moduli and internal friction is presented, together with Borne typical data obtained by the mechanical impulse method.
Measurements of the elastic compliance, the internal friction, and the induced dislocation voltage during deformation recovery indicate that the dislocation damping factor remains constant, while pinning and charging of the dislocation core occur by diffusion. The activation energy for charging by diffusion is 0.45 eV and for the pinning process is 0.65 eV.
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