Signal Processing for Coarse-Grained Materials

摘要

Reliable ultrasonic inspection of coarse-grained materials, such as cast stainless steel components in the primary piping loop of pressurized water reactors (PWRs) and dissimilar metal welds, has not been satisfactorily demonstrated to the utilities. The inspection for flaws is difficult because strong reflections from the grain boundaries could mask the flaw signal response;in addition, the ultrasonic beam can be redirected by the "wave guide" effect of the grain structure.nThis report discusses signal processing approaches that may be relevant to inspection of such materials. Specifically, spatial averaging--a proven technique for enhancing signals that exhibit spatial coherency—was found to be useful in v enhancing signal-to-noise ratio (SNR) for flaws whose lengths were larger than the average grain size.