scholarly journals A Modified Wavenumber Algorithm of Multi-Layered Structures with Oblique Incidence Based on Full-Matrix Capture

2021 ◽  
Vol 11 (22) ◽  
pp. 10808
Author(s):  
Bei Yu ◽  
Haoran Jin ◽  
Yujian Mei ◽  
Jian Chen ◽  
Eryong Wu ◽  
...  
Keyword(s):  
Wave Field ◽  
Oblique Incidence ◽  
Incident Angle ◽  
Layered Structures ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Extended Phase ◽  
Full Matrix ◽  
Coordinate Rotation ◽  
Non Destructive

Full-matrix capture (FMC)-based ultrasonic imaging provides good sensitivity to small defects in non-destructive testing and has gradually become a mainstream research topic. Many corresponding algorithms have been developed, e.g., the total focusing method (TFM). However, the efficiency of the TFM is limited, especially in multi-layered structures. Although the appearance of wavenumber algorithms, such as extended phase-shift migration (EPSM) methods, has improved imaging efficiency, these methods cannot be applied to cases with oblique incidence. Therefore, a modified wavenumber method for full-matrix imaging of multi-layered structures with oblique array incidence is proposed. This method performs a coordinate rotation in the frequency domain to adapt it to the oblique incidence. It then utilizes wave-field extrapolation to migrate the transmitting and receiving wave field to each imaging line, and a correlation imaging condition is used to reconstruct a total focused image. The proposed method can deal with any incident angle without precision loss. Moreover, it inherits the computational efficiency advantages of the wavenumber algorithms. The simulation and experimental results show that the proposed method performs better in terms of accuracy and efficiency than the TFM. Specifically, it is nearly 60 times faster than the TFM when processing an FMC dataset with a size of 4096 × 64 × 64.

Non-Destructive Detection of GIS Aluminum Alloy Shell Weld Based on Oblique Incidence Full Focus Method

2020 ◽  
Vol 1007 ◽  
pp. 105-110
Author(s):  
Xin Xin Wang ◽  
Cheng He ◽  
Pu Zhi Zhao ◽  
Yi Zheng ◽  
Shi Hao Jiang ◽  
...  
Keyword(s):  
Oblique Incidence ◽  
Near Field ◽  
Calibration Coefficient ◽  
Quantitative Detection ◽  
Imaging Method ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Field Range ◽  
Weld Defects ◽  
Non Destructive

In this paper, a new ultrasonic phased array full focus imaging method based on oblique incidence is proposed to solve the problem of the non-destructive testing of the internal defects in the GIS (gas insulated switchgear) shell welds. By using wedge coupling, the measured weld is far away from the near-field range of the transducer, and the detection angle range can be increased by changing the propagation direction of the acoustic beam. Based on Snell's law, the propagation characteristics of the ultrasonic wave in the interface are studied. On the basis of the conventional ultrasonic array matrix and the full focus imaging algorithm, by introducing the energy attenuation calibration coefficient of the acoustic wave propagation through the wedge, the correction amplitude of the specific focus point p(x, z) is obtained, The non-destructive testing of weld defects of GIS shell in the spot is carried out, and the test results show that the qualitative and quantitative detection of the weld defects can be well realized by using this method.

scholarly journals The effect of the diameter of the detector collimator on saturation thickness in gamma scattering measurement

2017 ◽  
Vol 1 (T3) ◽  
pp. 68-78
Author(s):  
Chuong Dinh Huynh ◽  
Nguyen Hoang Vo ◽  
Trang Thi Ngoc Le ◽  
Linh Thi Truc Nguyen ◽  
Tuyet Kim Tran ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Incident Angle ◽  
Target Thickness ◽  
Processing Technique ◽  
Scattering Method ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Saturation Thickness ◽  
Non Destructive ◽  
Scattering Measurement

The effect of the diameter of the detector collimator on the saturation thickness in gamma-scattering measurements is studied using the spectrum of singly scattering. Geometric arrangement of gamma-scattering measurement includes: a gamma-ray collimated beam with the energy of 662 keV emitted from 137Cs source is irradiated on a rectangular aluminium target with incident angle of 90o, and detector NaI(Tl) 5.1cmx5.1cm with collimator is used to record the scatterd gamma rays at scattered angle of 120°. The experimental measurements are carried out to obtain scattered spectra with various target thickness and diameter of detector collimator. The profile of the singly scattering and multiply scattering in the scattered spectra are determined by a spectrum processing technique based on the least squares fitting. The experimental results showed that the saturation thickness of the counts of singly scattering increases with increasing the window diameter of the detector collimator. These results will support for the non-destructive testing research of application of gamma-scattering method to determine the thickness or the defect of the sample.

Recording and Reconstruction of Digital Holography

2011 ◽  
Vol 105-107 ◽  
pp. 1812-1815
Author(s):  
Nan Hu ◽  
Li Chun Pu ◽  
Jian Wei Wei
Keyword(s):  
Wave Field ◽  
Digital Holography ◽  
Light Wave ◽  
Ccd Camera ◽  
Experimental Results ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Testing Method ◽  
Non Destructive

Holography is an important non-destructive testing method for its unique idea of recording the complete wave field, i.e. both the amplitude and the phase of the light wave scattered by the object. In digital holography (DH), hologram is recorded digitally by CCD and then numerically reconstructed in the computer. The biggest limitation for digital holography is the constraint of the resolution of the CCD camera and the recording distance is very important for DH. This article presents the principles of recording and reconstruction in digital holography. The experimental results and conclusion are also provided in this paper.

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