High-quality 2D and 3D imaging of multiple defects using laser ultrasonic and modal wave separation

In the field of non-destructive testing, defect imaging is the key to achieving precise identification. The synthetic aperture focus technique (SAFT) can be used for defect imaging of laser ultrasonic signals, but it is susceptible to artifact interference, resulting in a significant degradation of imaging quality. Therefore, this paper proposes a frequency-domain SAFT imaging method based on phase coherence factor (PCF) weighting to suppress background noise and artifacts. This method combines the efficient frequency-domain calculation capability of the phase migration method with the coherence characteristics of PCF, and corrects the imaging offset through an equivalent sound velocity model. Most importantly, a strong generalization and interactive quadratic polynomial fitting model that does not depend on the sound speed of the material is introduced to accurately extract the reflected wave signals, thereby achieving high-quality two-dimensional and three-dimensional imaging of multiple defects.