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Application of Arrival Time Profiles to AE Source Location by Neural Networks
Chlada, Milan ; Blaháček, Michal ; Převorovský, Zdeněk
The localization procedures using artificial neural networks (ANN) represent today highly effective, alternative approach to classical triangulation algorithms. Nevertheless, their application possibilities are limited due to several reasons. The main problems are in the collecting of sufficiently extensive training and testing data sets together with the non-portability of particular trained network to any other object. In recent time, a new ANN-based AE source location method using so-called signal arrival time profiles was proposed to overcome both limitations. The new way of signal arrival time characterization provides the ANN training on numerical models and allows the application of learned ANN on real structures of various scales and materials. In the paper, this new method is illustrated on experimental data obtained at complex aircraft structure part testing, and its remarkable advantages concerning the considerable extension of ANN application possibilities are discussed.
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Combined ESAM and DORT method in nonlinear ultrasonic spectroscopy
Vejvodová, Šárka ; Převorovský, Zdeněk ; Dos Santos, S.
Combination of ESAM (Excitation Symmetry Analysis Method) and DORT (Décomposition de l’Opérateur du Retournement Temporel) provides a powerful tool for detection and localization of defects by analysis of their nonlinear signature. Piezoelectric transducers are used for both excitation and data acquisition. Transmitters consequently emit the excitation signals and corresponding responses are measured by the array of receivers. The amplitude of excitation signals is variable as to separate the nonlinear parts of the measured signal. ESAM signal pre-processing is used for nonlinear parts extraction. Separated signal records form linear and nonlinear multistatic data matrices. DORT method is applied on data matrices to separate echoes of defects in the tested medium. Obtained data are used for evaluation of nonlinear parameters corresponding to separated defects and also for their localization. The procedure is completed by visualization of nonlinear signatures of detected defects.
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Nonlinear elastic wave spectroscopy in symbiosis with time reversal for localization of defects: TR-NEWS
Dos Santos, S. ; Vejvodová, Šárka ; Převorovský, Zdeněk
Using the symmetry invariance and reciprocity the classical NEWS methods are supplemented and improved by practically elaborated TR-NEWS procedure having the intrinsic property of enlarging frequency analysis bandwidth. Coded excitations have been generalized using Symmetry Analysis ESAM (Excitation Symmetry Analysis Method), including also the chirp-coded excitation, which improves the signal to noise ratio and enables harmonic imaging of complex specimen. In this paper, we propose a new NDT application of the above approaches implemented on a composite specimen with adhesive joints. The calibrated chirp-coded TR-NEWS imaging of the sample is obtained by using the symmetrical excitations, and pre- and post- signal processing. Localization of the scatterer is illustrated on 2D plot.
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Lokalizace zdrojů akustické emise pomocí neuronových sítí na základě časových profilů
Chlada, Milan ; Blaháček, Michal ; Převorovský, Zdeněk
Correct localization of acoustic emission (AE) sources is a basic requirement in AE analysis and consequent evaluation of damage mechanism. The localization procedures using artificial neural networks (ANN) represent today highly effective, alternative approach to classical triangulation algorithms. Nevertheless, their application possibilities are limited due to problematic collecting of sufficiently extensive training and testing data sets together with the non-portability of particular trained network to any other object. A new ANN-based approach, using so-called signal arrival time profiles, is proposed to overcome both limitations. Such approach provides the ANN training on numerical models and allows the application of learned ANN on real structures of various scales and materials. This enables considerable extension of ANN application possibilities. New method is illustrated on experimental data obtained during pen-tests on a steel plate, and its remarkable advantages are discussed.
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OPTIMIZED NUMBER OF SIGNAL FEATURES FOR IDENTIFICATION OF AE SOURCES
Chlada, Milan ; Převorovský, Zdeněk
Artificial neural networks (ANN) are effective instruments for identification of AE sources. The proper selection of extracted data features is complicated task in general data recognition. Standard AE signal parameters are often redundant or not relevant in recognition problem. Modifications of standard AE signal features are proposed in this paper as to reduce data redundancy. Set of extracted AE parameters is optimized by factor analysis and sensitivity analysis of recognizing neural networks. This optimization is illustrated by recognition of AE sources arising during fatigue tests performed on aircraft structure parts. Optimized AE signal features cover enough information with minimized number of parameters.
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Nelineární časově reversní ultrazvuková-tomografie
Převorovský, Zdeněk ; Krofta, Josef ; Převorovský, David
Nonlinear Elastic Wave Spectroscopy (NEWS) becomes new effective method for non-destructive testing of complex structures providing high sensitivity of damage detection. One of the most promising NEWS procedures is Nonlinear Time Reversal Acoustics (NLTRA) realizable in a lot of different ways. Common NLTRA procedure is mostly global, which means that localization of defect by this procedure can be often difficult. A modification of NLTRA is proposed in this paper, based on similar arrangement as ultrasonic tomography. Computer controlled switching between transmitting and receiving transducers is realized by specially designed high-voltage relay multiplexer.
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Ultrazvukové časově-reversní zrcadlo-numerická simulace v desce s defektem
Krofta, Josef ; Převorovský, Zdeněk
The time reversal mirror (TRM) is a method which can be effective in NDE of defects in materials. In this case an input ultrasonic wave is transmitted into the examined sample, then recorded by receiving transducers, time reversed and sent back by the same transducers. A simple numerical model of a solid plate was developed. Using this model, a simulation of TRM was performed. The propagation of ultrasonic waves used in time reversal method is studied. A number of tests with various configurations of transducers and defects and different methodology of the TRM procedure is simulated.
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