Rough Surface Effects of Aluminum Castings on Ultrasonic Sizing Algorithms

Several techniques for characterizing flaws and inclusions using ultrasonic scattering information have been developed in recent years. These algorithms assume a noise-free medium and are sensitive to perturbations in the acquired spectra. However, surface roughness and volumetric porosity effects alter the available data.In order to determine the effects of surface roughness typical of aluminum castings on inversion accuracy, a sequence of experiments was performed. Ultrasonic backscattering data were acquired from spheroidal defects in flat, smooth surfaced, diffusion bonded titanium samples. Next, the scattering spectra were perturbed using theoretically or experimentally determined transmission spectra obtained from rough surfaced cast aluminum samples. Inversion procedures were applied and results analyzed.