Ultrasonic testing with advanced signal processing for concrete structures

This paper proposes an ultrasonic test method for detecting flaws inside concrete structures. The ultrasonic testing can be valuable in locating flaws in materials. However, there are lots of coarse aggregates inside concrete and reflections from these aggregates influence ultrasonic test results. To reduce noise due to aggregates, an advanced signal processing method using the wavelet transform was applied to the ultrasonic signals. As-received ultrasonic signals were decomposed into several frequency components, which vary in width. From the decomposed result, significant frequency components, which include flaw signals, were chosen. To emphasize the flaw signals, products of chosen frequency components were calculated. The components were weighted according to these products, and signals were reconstructed. Flaws in the 3-dimensional image become increasingly evident by processing chosen frequency components. This signal processing using the wavelet transform could be a valuable method for increasing the reliability and should help in the interpretation of the test results.