Ultrasonic arrays for monitoring cracks in an industrial plant at high temperatures

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 46; no. 2; pp. 311 - 319
• Main Authors: Kirk, K.J., McNab, A., Cochram, A., Hall, I., Hayward, G.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.03.1999; Institute of Electrical and Electronics Engineers
• Subjects: Acoustical measurements and instrumentation; Acoustics; Analysing. Testing. Standards; Applied sciences; Arrays; Cross-disciplinary physics: materials science; rheology; Crystal defects; Exact sciences and technology; Frequency; Fundamental areas of phenomenology (including applications); Industrial engineering; Industrial plants; Lithium niobate; Manufacturing engineering; Materials science; Materials testing; Metals. Metallurgy; Monitoring; Nondestructive testing; Nondestructive testing: ultrasonic testing, photoacoustic testing; Phased arrays; Physics; Receiving; Steel; Structural steels; Temperature; Testing for defects; Time measurement; Transduction; acoustical devices for the generation and reproduction of sound; Transmitters; Piezoelectric sensor; Phased array; High temperature; Steel; Experimental study; MHz range; Temperature range 400-1000 K; Linear antenna; Lithium niobates; Testing equipment; Acoustic antenna; Measurement method; Non destructive test; Ultrasonic transducer; Monitoring; Transducer network; Crack
• ISSN: 0885-3010
• DOI: 10.1109/58.753019

A piezoelectric linear array structure has been designed to operate at temperatures up to 400/spl deg/C for nondestructive testing of steel components of a hot industrial plant. It is intended that these arrays be fixed permanently to the test subject so that known defects can be monitored by comparing measurements taken over a period of time without needing to shut down the plant. The arrays are used in pairs: the transmitter is a phased array producing a variable angle steered beam, and a second array is used for receiving. The defect can be identified from a series of scans collected from individual elements of the second array. A simple monolithic array structure was used, based on a single crystal of lithium niobate and operating in the frequency range 3 to 5 MHz. Prototype devices have 64 elements on a 0.5 mm pitch. Simulated defects in steel blocks have been scanned at high temperatures to illustrate the arrays' capability for nondestructive testing. The results suggest an accuracy better than 1 mm in finding the location of crack tips.