Signal processing for coarse-grained materials: Interim report

Technical Report · Wed Jul 01 04:00:00 EDT 1987

OSTI ID:6305020

Selby, G P; Shankar, R; Hunt, J F

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. This 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 enhancing signal-to-noise ratio (SNR) for flaws whose lengths were larger than the average grain size. Three specimens of PWR main coolant piping, each a cast steel elbow welded to forged steel containing fatigue flaws, were examined with a personal computer (PC)- based data acquisition and imaging system developed under EPRI funding. In addition, an axial flaw intentionally placed in the Inconel weld of a nozzle-to-safe-end mockup obtained from the canceled Phipps Bend plant was examined. The PC-based system was modified to include software capabilities to perform signal averaging and filtering. The images produced before and after signal processing showed improvements in flaw detectability.

• Research Organization: Jones (J.A.) Applied Research Co., Charlotte, NC (USA); Electric Power Research Inst., Palo Alto, CA (USA)
• OSTI ID: 6305020
• Report Number(s): EPRI-NP-5329; ON: TI87920531
• Country of Publication: United States
• Language: English

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