Ultrasonic Hysteresis Absorption in Polymers
NAVAL ORDNANCE LAB WHITE OAK MD
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Ultrasonic absorption measurements were made in PMMA, polyethylene, and polyethylene oxide as functions of frequency, temperature, and strain. At room temperature, all three polymers show a hysteresis type absorption that extends at least over the frequency range from 1 Hz to 10 to the 7th power Hz, as shown by using literature values for results at 1 Hz. There is no strain dependence to the absorption in any of the polymers in the strain range from 10 to the minus 9th power to 0.000001. The mechanism responsible for the hysteresis absorption is postulated to be the trapping of the polymer in one of its many local metastable potential energy minima. This mechanism leads to the prediction that the hysteresis absorption should be a linearly decreasing function of volume and this prediction is in reasonable agreement with the experimental data.