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Infrastructure Technology Institute

The 52nd meeting of the acoustic emission
working group

The Infrastructure Technology Institute hosted the 52nd meeting of the Acoustic Emission Working Group (AEWG) October 19-21, 2009, in Sturgeon Bay, Wisconsin. AEWG is an international organization dedicated to advancement of the theory and practice of acoustic emission (AE) testing. AE refers to the phenomenon by which materials under stress emit noises – sometimes audible, as with the “tin cry” known to metalworkers, but more often inaudible ultrasonic frequencies – and to the non-destructive evaluation technique based upon analysis of these noises. ITI is a leader in application of AE techniques to large civil structures, especially steel bridges. While a wide variety of AE applications were featured at the 2009 meeting, civil infrastructure was a special area of focus. Sturgeon Bay was selected as the meeting site in part because it allowed participants to tour steel bridges.

In keeping with AEWG’s custom, the first day of the meeting consisted of a series of hour-long primer sessions intended to introduce novices to basic AE concepts while refreshing and expanding the knowledge of veteran AE workers. The morning featured lectures on AE instrumentation and basic analysis as well as feature-based analysis by Rick Nordstrom of Portland State University and Tomoki Shiotani of Kyoto University, respectively. Jihui Li of Inova Fairfax (Virginia) Hospital closed the morning with an overview of biomedical applications of AE. The entire afternoon was dedicated to civil infrastructure applications. ITI research engineers David Kosnik and Daniel Marron presented a summary of the Institute’s work on AE localization and characterization of cracks in steel highway bridges. Kosnik and Marron also discussed AE for localization of mechanical noise sources on large movable structures.

The second and third days of the meeting were filled with technical presentations and lively discussion. Presentations ranged from AE sensor design and data analysis techniques to practical applications ranging from materials science to medicine, civil structures, and aerospace. Immediately following a tour of one of the bridges in downtown Sturgeon Bay, ITI research engineers David Kosnik and Daniel Marron presented their recent work on AE for localization of the source of unsettling “banging” noises observed on a lift bridge. Because sound travels about 17 times faster in steel than in air, it is nearly impossible to locate the source of such noises by ear. Fortunately, AE source location techniques can provide unambiguous results; once the noise source is identified, it is possible to determine the cause.

On Tuesday evening, an awards dinner was held during a boat tour of Sturgeon Bay. Attendees were treated to up-close views of the three bridges over the bay and adjoining ship canal. Masayasu Ohtsu of Kumomoto University was awarded the AEWG Gold Medal for his work on AE analysis of concrete, including investigation of rebar corrosion and corrosion-induced cracking.