A novel thermosonic imaging system for non-destructive testing

Abstract

Abstract. Thermosonic infrared (Sonic IR) imaging is a new non-destructive testing (NDT) technique that uses highfrequency sonic excitation together with infrared (IR) detection to image surface and subsurface defects. A conventional Sonic IR imaging system employs an ultrasonic welder, which is designed to operate at a single frequency. This single frequency ultrasonic source has been found to yield a "blind zone" for NDT due to the formation of standing waves inside the test piece. To overcome this limitation, a spring loaded ultrasonic transducer was used to generate the desired multifrequency acoustic chaos in the test object [1]. The limitation of the spring loaded ultrasonic transducer is its repeatability and reproducibility for field applications. In this work, we present the development of a novel thermosonic imaging system, which is capable of exciting the ultrasonic transducer at different frequencies for thermosonic NDT to overcome the limitations associated with a single frequency power source as well as the spring loaded transducer design. A comparison of experimental results will be made between the single frequency and the developed multi-frequency thermosonic NDT systems.

Recent developments in vibrothermography

“…For distinguishing damaged regions from surroundings, multi-frequency excitation is a very useful method which enables that the resulting heat generation covers the whole length of the material [84,85]. There are two advantages of multi-frequency excitation; first, reducing the number of excitation locations needed to form a complete picture of the defects present within a material; and second, reducing the number of blind zones that cannot be detected with single frequency implementation [86].…”