Wave-Based Acoustic Shearography for Defect Imaging

Acoustic shearography technique is a wave-based shearography method. In acoustic shearography, acoustic or ultrasonic waves are used to provide stress loading in the testing materials. Due to the deep penetration of acoustic waves and the flexibility of wave focusing control, acoustic shearography technique can detect deep subsurface defects in solid materials at the optical imaging speed. In this paper, the working principles, and the system setup of the acoustic shearography system are to be presented. Various acoustic excitation methods including acoustic excitation with dispersive acoustic transducers, directional and focusing acoustic wave transducers and pulsed laser beams are discussed. The applications of acoustic shearography for imaging of defects in thick metal structures are demonstrated. The acoustic shearography technique provides a feasible and practical solution for fast NDT of thick and large area structures.