Width and depth gauging of rectangular subsurface defects based on all-optical laser-ultrasonic technology. (30th March 2022)

• Record Type: Journal Article
• Authors: Chen, Cheng; Sun, Anyu; Ju, Bing-Feng; Wang, Chuanyong
• Is Part Of: Applied acoustics. Volume 191(2022)
• Publication Date: 2022-03-30
• Subjects: All-optical laser-ultrasonic -- Rayleigh wave -- Ultrasonic wave -- Rectangular subsurface defect -- Width gauging -- Depth gauging; Acoustical engineering -- Periodicals; Periodicals; 620.2
• DOI: 10.1016/j.apacoust.2022.108684
• Languages: English
• ISSNs: 0003-682X

Abstract

Highlights: An all-optical laser-ultrasonic system was developed. Mode-converted Rayleigh waves from rectangular subsurface defects were detected. A detection method for gauging rectangular subsurface defects was proposed. Width and depth of rectangular subsurface defects were successfully gauged. Abstract: In this study, width and depth of rectangular subsurface defects have been successfully gauged based on all-optical laser-ultrasonic technology. A specific all-optical laser-ultrasonic system has been developed to obtain Rayleigh waves from subsurface defects. Time domain and frequency domain analysis of the obtained Rayleigh waves show that most of the high-frequency Rayleigh waves with small wavelengths transmit the subsurface defect. Only a small part of the low-frequency Rayleigh waves with large wavelengths are reflected by the subsurface defect. This phenomenon is completely different from that of surface defect, because surface defect reflects high-frequency Rayleigh waves and allows low-frequency Rayleigh waves to transmit. In addition, it is found that the transmitted mode-converted Rayleigh wave has the smallest amplitude but the highest center frequency compared with other obtained incident, reflected mode-converted and transmitted Rayleigh waves. Width and depth of subsurface defects are measured by the proposed three-step detection method, which is based on the arrival time of the incident, reflected mode-converted, transmitted and transmitted mode-converted Rayleigh waves, as well as the movement distance of samples. Agreement between experimental results and digital microscope measurement reference-results indicates applicability of the proposed three-step detection method in simultaneous measuring width and depth of rectangular subsurface defects.