Effects of Defect Size and Number Density on the Transmission and Reflection of Guided Elastic Waves
MIT Lincoln Laboratory Lexington United States
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We explore the scattering of guided elastic waves in plastic cylinders by wavelength-sized defects. A random field of defects is introduced into the cylinder in a localized region, a photoacoustic source generates elastic waves on one side of the damaged region, and then two ultrasound transducers measure the amplitude of the waves transmitted and reflected by the damaged region. We found that for defects approximately 3 in diameter that the transmission amplitude decays exponentially in the volumetric number density of defects. Furthermore, we discovered that the for a constant defect density, in the Mie regime, there is not statistically significant transmission amplitude variation between different defect sizes. Additionally, in the Mie regime, the reflected wave due to backscatter is too small to be detected with our equipment.