Synchronous Multipoint Laser Doppler Vibrometer Measurements in Surface Crack Localization and SAFT Imaging

Nondestructive testing techniques are usually required to analyze the microstructure of surface cracks in metal components in various harsh environments and complex structures. The out-of-plane displacement caused by laser-induced surface acoustic waves (SAWs) is capable of carrying information about the specimen surface structure, which can be used as the most direct method for monitoring surface cracks. To meet the rapid measurement requirements for vibration surfaces, we developed a synchronized two-dimensional (2D) laser Doppler vibrometer system. This multipoint vibrometer was capable of SAW detection across a 3 × 3 mm² area by a 4 × 4 measurement lattice. The imaging results of surface cracks on the aluminum block substantiated that the system’s capability to localize cracks with an accuracy exceeding 91.3%. The proposed 2D laser Doppler vibrometer array was effective for synchronous vibration measurements in nondestructive testing of metallic surface cracks, paving the way to high-sensitivity nondestructive testing applications for metallic components under strict measurement conditions.