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Application of a matched filter approach for finite aperture transducers for the synthetic aperture imaging of defects
Published in
2010
Volume: 57
   
Issue: 6
Pages: 1368 - 1382
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. © 2006 IEEE.
About the journal
JournalIEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
ISSN08853010
Open AccessNo
Concepts (36)
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    A-center
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    ALUMINUM BLOCK
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    Computational burden
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    CRACK-LIKE DEFECTS
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    FDTD METHOD
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    FINITE APERTURE
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    Finite size
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    FINITE TRANSDUCERS
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    FINITE-DIFFERENCE TIME-DOMAIN ALGORITHMS
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    Gaussian white noise
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    IN-PIPE
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    PHASED ARRAY PROBES
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    PHASED ARRAY TRANSDUCERS
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    PHASED ARRAYS
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    SCAN MODE
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    SIDE-DRILLED HOLE
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    SINGLE ELEMENT
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    SYNTHETIC APERTURE FOCUSING TECHNIQUES
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    SYNTHETIC APERTURE IMAGING
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    TO EFFECT
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    TRANSDUCER CONFIGURATION
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    Algorithms
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    Finite difference time domain method
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    Gaussian beams
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    Imaging systems
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    Impulse response
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    MATCHED FILTERS
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    Probes
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    Surface defects
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    Synthetic apertures
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    Transducers
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    Ultrasonic applications
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    Ultrasonics
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    Wave propagation
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    White noise
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    ANTENNA PHASED ARRAYS