Advanced Excitation Symmetry Analysis Method (ESAM) for improved automated ultrasonic testing of polished materials
One of the strategic plans of the international NDT community is to define standards for developing advanced and digitalized non-destructive testing for automated set-up in mass production [1,2]. Excitation Symmetry Analysis Method (ESAM) are new coded signal processing tools exploring symmetry prop...
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Published in | E-journal of Nondestructive Testing Vol. 29; no. 6 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
01.06.2024
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Online Access | Get full text |
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Summary: | One of the strategic plans of the international NDT community is to define standards for
developing advanced and digitalized non-destructive testing for automated set-up in mass
production [1,2]. Excitation Symmetry Analysis Method (ESAM) are new coded signal
processing tools exploring symmetry properties [3]. ESAM method aims to extract the
nonlinearity from an ultrasound output by studying the property of symmetry of the transfer
function. More precisely, the extraction of nonlinearity is done using basis function associated
to a group which is associated to an a priori transfer function. As soon as the linear tomography
uses the invariant properties of amplitude dependence, nonlinear tomography should exploit
the invariance properties (or symmetry properties) of the complex system. Consequently, the
invariance of the stationary properties of a complex medium would be supposed to be associated
to a signature of the degradation, that will be extracted with advanced signal processing tools.
The idea remains the same: studying the symmetry and more precisely the time reversal one
and the inversion. A signal processing is used to measure discrepancies in the autocorrelation
function (output signal called chirp coda) for two inputs: a signal and its inversion (pulse
inversion). The experiments were done on different sample with and without cracks. It has been
shown that when the nonlinearities are extracted from the chirp coda amplitude are non-
negligible in crack area and nonlinearities are out of phase. Then, mixing symmetries like time
reversal and pulse inversion enable the detection of defect that are difficult to detect with
conventional ultrasound method. Indeed, for such crack a destructive mechanical analysis
called Jomini is done where the material is polished and examined with microscope. The
sensitivity improvement of chirp-coded signal processing has been validated in various domains.
Coded excitation techniques, used in communication systems such as radar and sonar provide
improved SNR without increasing the amplitude of excitation. The typical test equipment
consists of a preamplifier Juvitek TRA-02 (0.02 - 5 MHz) connected to a computer, an amplifier
ENI model A150 (55 dB at 0.3-35 MHz), a shear wave transducer Technisonic (2.25 MHz),
and a longitudinal wave transducer Panametrics V155 (5 MHz). The experimental device was
tested with the V3 calibration block, improved, and specially scaled in order to access to a wide
range of multivalued parameters: mechanical properties, ultrasonic parameters (celerity and
attenuation) and local geometric data. |
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ISSN: | 1435-4934 1435-4934 |
DOI: | 10.58286/29951 |