Air-coupled ultrasonic testing

Article By:

Chimenti, Dale E. Department of Aerospace Engineering, Iowa State University, Ames, Iowa.

Last reviewed:2008

DOI:https://doi.org/10.1036/1097-8542.YB084590

Ultrasonic testing is the process of introducing high-frequency stress waves, or ultrasound, into an object for determining something about the object's internal structure or makeup, or the presence of material anomalies within the object. This process consists typically of three stages: production of the ultrasonic wave by a device that changes electrical impulses into stress waves and the wave's propagation through some sound-supporting medium to the object under study; interaction of the ultrasound with the object, including the effects of the object's shape, material constituents, and the presence of internal structure; and, finally, reflection, or more generally, scattering of the incident sound wave, either back to the device that originally produced the sound or to another similar device (Fig. 1). Sound waves are generated when electrical impulses are transformed into mechanical vibrations by the sending transducer. The resulting sound wave interacts with the object under test and reflects, or scatters, in many directions. Then a portion of the scattered field can be received and detected, either by the same device working in reciprocal mode as a detector or by another similar device. This is the principle of ultrasonic testing.

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