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Locally Optimal Subsampling Strategies for Full Matrix Capture Measurements in Pipe Inspection

: Krieg, Fabian; Kirchhof, Jan; Pérez, Eduardo; Schwender, Thomas; Römer, Florian; Osman, Ahmad

Volltext urn:nbn:de:0011-n-6349276 (4.9 MByte PDF)
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Erstellt am: 21.5.2021

Applied Sciences 11 (2021), Nr.9, Art. 4291, 14 S.
ISSN: 2076-3417
Deutsche Forschungsgemeinschaft DFG
GA 2062/5-1; CoSMaDU
Fraunhofer-Gesellschaft FhG
Fraunhofer Internal Programs; Attract 025-601128
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IZFP ()
Total Focusing Method (TFM); compressive sensing; Fast Iterative Shrinkage-Thresholding algorithm (FISTA); full matrix capture; NDT methods; signal reconstruction; defects

In ultrasonic non-destructive testing, array and matrix transducers are being employed for applications that require in-field steerability or which benefit from a higher number of insonification angles. Having many transmit channels, on the other hand, increases the measurement time and renders the use of array transducers unfeasible for many applications. In the literature, methods for reducing the number of required channels compared to the full matrix capture scheme have been proposed. Conventionally, these are based on choosing the aperture that is as wide as possible. In this publication, we investigate a scenario from the field of pipe inspection, where cracks have to be detected in specific areas near the weld. Consequently, the width of the aperture has to be chosen according to the region of interest at hand. On the basis of ray-tracing simulations which incorporate a model of the transducer directivity and beam spread at the interface, we derive application specific measures of the energy distribution over the array configuration for given regions of interest. These are used to determine feasible subsampling schemes. For the given scenario, the validity/quality of the derived subsampling schemes are compared on the basis of reconstructions using the conventional total focusing method as well as sparsity driven-reconstructions using the Fast Iterative Shrinkage- Thresholding Algorithm. The results can be used to effectively improve the measurement time for the given application without notable loss in defect detectability.