Full-Field Strain Imaging of Ultrasonic Waves in Solids

Abstract

Lamb waves are well-known guided waves propagating in thin plates. They are often considered as a convenient tool for non-destructive testing but one of the major challenges consists in measuring them [1]. Several techniques allow one to do this. First, ultrasonic transducers provide point measurement of the vibration amplitude. However, this is only a point measurement and does not provide very much spatial resolution even if several transducers are used simultaneously. Shearography on the other hand does provide a map of surface slopes that can for instance be related to the presence of a delamination. However, this technique does easily not allow for time-resolved measurements. Finally, the most versatile is certainly scanning laser Doppler vibrometry (SLDV) which provides excellent temporal resolution. The spatial resolution arises from the scanning of the surface. This takes time and requires periodic loading with stable excitation over the duration of the scan. More details about these techniques can be found in [1].