Journal ArticleDOI
Application of a matched filter approach for finite aperture transducers for the synthetic aperture imaging of defects
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TLDR
These studies confirm that MFA is an alternative to SAFT with little additional computational burden and can also be applied blindly, like SAFT, to effect synthetic focusing with distinct advantages in treating finite transducer effects, and in handling steered beam inspections.Abstract:
The suitability of the synthetic aperture imaging of defects using a matched filter approach on finite aperture transducers was investigated. The first part of the study involved the use a finite-difference time-domain (FDTD) algorithm to simulate the phased array ultrasonic wave propagation in an aluminum block and its interaction with side-drilled hole-like defects. B-scans were generated using the FDTD method for three active aperture transducer configurations of the phased array (a) single element and (b) 16-element linear scan mode, and (c) 16-element steering mode. A matched filter algorithm (MFA) was developed using the delay laws and the spatial impulse response of a finite size rectangular phased array transducer. The conventional synthetic aperture focusing technique (SAFT) algorithm and the MFA were independently applied on the FDTD signals simulated with the probe operating at a center frequency of 5 MHz and the processed B-scans were compared. The second part of the study investigated the capability of the MFA approach to improve the SNR. Gaussian white noise was added to the FDTD generated defect signals. The noisy B-scans were then processed using the SAFT and the MFA and the improvements in the SNR were estimated. The third part of the study investigated the application of the MFA to image and size surface-crack-like defects in pipe specimens obtained using a 45° steered beam from a phased array probe. These studies confirm that MFA is an alternative to SAFT with little additional computational burden. It can also be applied blindly, like SAFT, to effect synthetic focusing with distinct advantages in treating finite transducer effects, and in handling steered beam inspections. Finally, limitations of the MFA in dealing with larger-sized transducers are discussed.read more
Citations
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Journal ArticleDOI
A sparse reconstruction algorithm for ultrasonic images in nondestructive testing.
Giovanni Alfredo Guarneri,Daniel R. Pipa,Flávio Neves Junior,Lúcia Valéria Ramos de Arruda,Marcelo V. W. Zibetti +4 more
TL;DR: In this paper, an image reconstruction algorithm based on regularized least squares using a l 1 regularization norm was proposed to reconstruct an image of a point-like reflector, using both simulated and real data.
Journal ArticleDOI
Hybrid Seminumerical Simulation Scheme to Predict Transducer Outputs of Acoustic Microscopes
TL;DR: A seminumerical simulation method called SIRFEM is presented, which enables the efficient prediction of high-frequency transducer outputs and is able to predict reflections at inner structures as well as multiple reflections between those structures and the specimen's surface.
A Sparse Reconstruction Algorithm for Ultrasonic Images in
Giovanni Alfredo Guarneri,Daniel Rodrigues Pipa,Flávio Neves Junior,Lúcia Valéria,Ramos de Arruda,Marcelo Victor,Wüst Zibetti +6 more
TL;DR: A new image reconstruction algorithm for ultrasonic NDT that reconstructs images from A-scan signals acquired by an ultrasonic imaging system with a monostatic transducer in pulse-echo configuration based on regularized least squares using a l1 regularization norm is presented.
References
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Journal ArticleDOI
Beam focusing behavior of linear phased arrays
L. Azar,Y. Shi,Shi-Chang Wooh +2 more
TL;DR: In this article, the authors derived the pressure distribution for beam focusing, and showed that the directivity of focusing converges to that of steering in the far field of the array.
Journal ArticleDOI
A new approach to calculate the field radiated from arbitrarily structured transducer arrays
B. Piwakowski,K. Sbai +1 more
TL;DR: A efficient time-domain algorithm, based on the spatial pulse response approach, is proposed for the determination of the acoustic fields radiated by means of acoustical sources.
Journal ArticleDOI
A New Synthetic-Aperture Focusing Method for Ultrasonic B-Scan Imaging by the Fourier Transform
TL;DR: In this article, the Fourier domain recon-struction (FDR) method was proposed for ultrasonic E-scan imaging, which involves the two-dimensional Fourier transform.
Journal ArticleDOI
Synthetic aperture imaging using sources with finite aperture: deconvolution of the spatial impulse response.
TL;DR: A time-domain algorithm for deconvolution of the transducer's spatial impulse responses (SIRs) is developed that is based on a minimum mean square error (MMSE) criterion and takes the form of a spatiotemporal filter that compensates for the SIRs associated with a finite-sized transducers at every point of the processed image.
Journal ArticleDOI
Crack detection and sizing technique by ultrasonic and electromagnetic methods
TL;DR: In this paper, a 256-channel array system has been developed for the inspection of weldment of BWR internal components such as core shrouds and the TOFD crack sizing technique also can be applied using this system.