Browsing by Subject "Ultrasonic waves"

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    Phenomena in the propagation of ultrasonic vibrations in nickel wire
    (1987) Coulter, John Dallaway
    A wave-train-echo technique, with repeated forward-and-return travels of the signal, was used to study the propagation of ultrasonic waves in nickel wire. In particular, the origin of often observed anomalous waves in nickel wire was investigated. A possible explanation of an aspect of the phenomenon was devised. During continuing investigation of the phenomenon of anomalous waves, an unexpected effect of stress on the attenuation of ultrasonic waves in annealed nickel wire was observed. Attention was transferred to the new phenomenon, and extensive experimental work carried out to measure the effects of direct and flexural stress on the attenuation. The effect was found to occur with torsional stress also. Computer-aided determinations of attenuation were made from the experimental readings of signal strength for variations of stress and signal frequency. A detailed study and documentation of known processes of attenuation of acoustic vibrations in solids was made. Indications of the nature of the mechanism of stress-dependent attenuation have been sought, and a tentative conclusion arrived at.