Abstract
Phase velocity and attenuation of compressional and shear waves in the two materials PMMA and Eccosorb MF-117 were measured as function of frequency and temperature, using a broadband through-transmission technique. Two pairs of transducers were used for the measurements, one pair with center frequency 5 MHz, covering the frequency range from 2.5 MHz to 6 MHz, and one pair with center frequency 10 MHz, covering the range from 5.5 MHz to 10.5 MHz. The measured results for PMMA showed a good agreement with published values, thus verifying the accuracy of our approach. From 2.5 MHz to 6 MHz, a negative dispersion of 2 m/s/MHz was observed for the compressional wave velocity in PMMA. The dispersion for Eccosorb MF-117 in the same frequency range was also negative, and measured to 5.5 m/s/MHz. The dispersion value did not change over the investigated temperature range, from 20°C to 37°C, although the phase velocities changed with temperature. The shear wave velocity showed a similar trend, with negative dispersion 2 m/s/MHz for PMMA and 4.5 m/s/MHz for Eccosorb MF-117. The attenuation of both compressional and shear waves in both materials increased with frequency over the investigated frequency ranges. Increasing the temperature from 20°C to 37°C caused a decrease of 3% and 5% in the phase velocity of PMMA and Eccosorb MF-117, respectively. Over the same temperature range, the attenuation increased by 35% in PMMA and by 30% in Eccosorb MF-117.
