Non-destructive laser-ultrasonic Synthetic Aperture Focusing Technique (SAFT) for 3D visualization of defects

Photoacoustics

Chu Chen¹  Kai-Ning Ying²  Lu-Nan Dai²  Chen-Yin Ni²  Wei-Wei Kan³  Ling Yuan³  Zhong-Hua Shen³ 

[1] Corresponding authors.;School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China;School of Science, Nanjing University of Science and Technology, Nanjing 210094, China;

关键词: Laser ultrasound;    Synthetic Aperture Focusing Technique (SAFT);    Non-destructive Test (NDT);    Imaging algorithm;   

DOI  :  

来源: DOAJ

【 摘 要 】

The Laser Ultrasonic (LU) technique has been widely studied. Detected ultrasonic signals can be further processed using Synthetic Aperture Focusing Techniques (SAFTs), to detect and image internal defects. LU-based SAFT in frequency-domain (F-SAFT) is developed to visualize horizontal hole-type defects in aluminum. Bulk acoustic waves are non-destructively generated by irradiating a laser line-source, and detected using a laser Doppler vibrometer at a point away from the generation. The influence of this non-coincident generation-detection on the equivalent acoustic velocity used in the algorithm is studied via velocity mappings. Because the wide-band generation characteristic of the LU technique, frequency range selections in acoustic wave signals are implemented to increase Signal-to-Noise Ratio (SNR) and reconstruction speed. Results indicate that by using the LU F-SAFT algorithm, and incorporating optimizations such as velocity mapping and frequency range selection, small defects can be visualized in 3D with corrected locations and improved image quality.

【 授权许可】

Unknown