Defect imaging based on laser ultrasonic frequency domain synthetic aperture focusing technology with separated generation–detection and 2-D equivalent velocity mapping

Dai, Lu-Nan; Ni, Chao; Ying, Kai-Ning; Yuan, Lei; Kan, Weiwei; Shen, Zhonghua

doi:10.1016/j.optlastec.2022.108485

Cited by 13 publications

(10 citation statements)

References 31 publications

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“…Synthetic aperture focusing technology (SAFT) uses small aperture arrays to dynamically synthesize equivalent virtual large apertures, which can achieve high imaging resolution with small aperture arrays, and is especially suitable for high-resolution automatic detection of cylindrical components [ 22 , 23 , 24 ]. Dai [ 25 ] proposed an accurate frequency-domain synthetic aperture focusing technology based on 2D equivalent velocity mapping to detect and image internal defects in specimens. Ying [ 26 ] proposed a Multi-mode Time-domain SAFT algorithm, which can be used to superimpose SAFT images generated by single-mode ultrasound signals to obtain a better defect shape.…”

Section: Introductionmentioning

confidence: 99%

Research on Photoacoustic Synthetic Aperture Focusing Technology Imaging Method of Internal Defects in Cylindrical Components

Zhang,

Li,

Chen

et al. 2023

Sensors

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Cylindrical components are parts with curved surfaces, and their high-precision defect testing is of great significance to industrial production. This paper proposes a noncontact internal defect imaging method for cylindrical components, and an automatic photoacoustic testing platform is built. A synthetic aperture focusing technology in the polar coordinate system based on laser ultrasonic (LU-pSAFT) is established, and the relationship between the imaging quality and position of discrete points is analyzed. In order to verify the validity of this method, small holes of Φ0.5 mm in the aluminum alloy rod are tested. During the imaging process, since a variety of waveforms can be excited by the pulsed laser synchronously, the masked longitudinal waves reflected by small holes need to be filtered and windowed to achieve high-quality imaging. In addition, the influence of ultrasonic beam angle and signal array spacing on imaging quality is analyzed. The results show that the method can accurately present the outline of the small hole, the circumferential resolution of the small hole is less than 1° and the dimensional accuracy and position error are less than 0.1 mm.

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Section: Introductionmentioning

confidence: 99%

Research on Photoacoustic Synthetic Aperture Focusing Technology Imaging Method of Internal Defects in Cylindrical Components

Zhang,

Li,

Chen

et al. 2023

Sensors

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“…To address this problem, in recent years, several fascinating LU imaging methods have been developed. [23][24][25][26][27][28] The LU-based total focusing method (TFM) imaging can obtain accurate imaging of defects using a fullmatrix capture. 25 Although this technique can effectively improve detection sensitivity and imaging resolution, TFM requires high computational complexity of the imaging algorithm.…”

Section: Introductionmentioning

confidence: 99%

“…3 LU-based synthetic aperture focusing technique (SAFT) is also an internal defect imaging method developed in recent years, which employs a point-by-point scanning approach to improve the lateral resolution of imaging in the post-processing. 24 Furthermore, SAFT algorithms can be classified into the time domain synthetic aperture focusing technique (T-SAFT) 21,23,29 and the frequency domain synthetic aperture focusing technique (F-SAFT) 4,24,27,28 depending on the post-processing process. Compared to the T-SAFT, the F-SAFT possess the potential to be applied to real-time imaging because of the faster computational speed.…”

Section: Introductionmentioning

confidence: 99%

“…The separated excitation and detection for scanning are commonly used to avoid the effect of the large thermal expansion displacement caused by the excitation laser on the target signal in LU, which could affect the equivalent velocity in the F-SAFT algorithm, as well as the imaging quality. 27 To solve this problem, the equivalent velocity in the F-SAFT algorithm can be optimized by creating a 2D equivalent velocity mapping. 27 In addition, the laser can generate multiple modes of ultrasound waves simultaneously, and each mode of the wave possesses different amplitudes of reflected signals at different locations of the defect due to the exceptional directionality of the wave mode.…”

Section: Introductionmentioning

confidence: 99%

“…27 To solve this problem, the equivalent velocity in the F-SAFT algorithm can be optimized by creating a 2D equivalent velocity mapping. 27 In addition, the laser can generate multiple modes of ultrasound waves simultaneously, and each mode of the wave possesses different amplitudes of reflected signals at different locations of the defect due to the exceptional directionality of the wave mode. 31 Therefore, fusion imaging incorporating SAFT images generated by multiple ultrasonic wave modes can be used to improve the quality of defect imaging.…”

Section: Introductionmentioning

confidence: 99%

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F-SAFT based on laser-induced directional multimode ultrasound for defect imaging

Dai,

NI,

Ying

et al. 2023

Structural Health Monitoring

Self Cite

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In conventional laser ultrasonic (LU) single-mode frequency domain synthetic aperture focusing technique (F-SAFT) imaging, the precision of the imaged defect profile is limited due to the influence of the directionality of laser-induced ultrasound and the directionality of detection. To solve this problem, LU-based F-SAFT imaging with the shear wave, longitudinal wave, and mode-converted wave is proposed in this article. In the experiment, multimode bulk waves are excited by a pulsed laser, and a laser Doppler vibrometer is employed to detect ultrasound waves. The F-SAFT imaging is performed with single-mode and multimode ultrasound wave signals, respectively. The results show that F-SAFT imaging fusing three mode signals (shear, longitudinal, and mode-converted waves) improves the range of the upper surface of the imaged defect by nearly two times. In addition, the profile of the imaged defect is more complete than that of using a combination of both longitudinal and shear waves. By analyzing the influence of the directionality of laser-induced ultrasound and the detection directionality caused by the out-of-plane ultrasound component on the imaging results, a theoretical approach is used to select a reasonable excitation–detection distance for the use of multimode-fused F-SAFT algorithm. Furthermore, the feasibility of the theoretical approach is verified by the experimental results.

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Non-contact detection of subsurface defects in metallic bars with small diameter using laser-generated Rayleigh waves: From localization to quantification

Zhang,

Xu,

Wang

et al. 2024

Journal of Manufacturing Processes

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Defect imaging based on laser ultrasonic frequency domain synthetic aperture focusing technology with separated generation–detection and 2-D equivalent velocity mapping

Cited by 13 publications

References 31 publications

Research on Photoacoustic Synthetic Aperture Focusing Technology Imaging Method of Internal Defects in Cylindrical Components

Research on Photoacoustic Synthetic Aperture Focusing Technology Imaging Method of Internal Defects in Cylindrical Components

F-SAFT based on laser-induced directional multimode ultrasound for defect imaging

Non-contact detection of subsurface defects in metallic bars with small diameter using laser-generated Rayleigh waves: From localization to quantification

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