Porosity assessment of flat smooth surface cast aluminum samples by ultrasonic attenuation spectroscopy were found to be in good agreement with other porosity assessment methods, e. g., weight-density, and optical techniques [1], Ultrasonic results were also obtained for samples with their as-cast rough surface intact. The volume fraction of porosity in these samples were unacceptably underestimated [2]. Since it is not feasible to maintain a smooth surface, especially for large castings prior to ultrasonic assessment, a technique to compensate for surface roughness was considered.
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