Comparison of random and periodic rough surfaces by ultrasonic attenuation and frequency distribution

Abstract

Flow accelerated corrosion generates not only pipe-wall thinning but also roughness on an inside wall. In some flow conditions, the increase in roughness can increase the mass transfer coefficient by up to 80%. It is then very important to have an evaluation tool to monitor and quantify the roughness of a pipe. This study aims to estimate the roughness by using ultrasonic attenuation. The advantage of using ultrasonic attenuation is that it utilizes the signals measured by existing ultrasonic probes, and does not require significant changes to the equipment. To evaluate the inner rough surface, this study compares ultrasonic attenuations on random and periodic rough surfaces. We used an ultrasonic broadband probe on specimens with random and periodic rough surfaces in experiments. The results indicate a significant difference between the attenuation values estimated on random and periodic roughness. In addition, attenuation of amplitude at specific frequencies also was observed. These specific frequencies implied having the potential to estimate the pitch of periodic flaws on the rough surface.