Home > Search Results: "Defektoskopie 2008 /38./"
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National Repository of Grey Literature 4 records found  Search took 0.00 seconds. 
NONDESTRUCTIVE EVALUATION OF CONCRETE STRUCTURES BY NONLINEAR ULTRASONIC SPECTROSCOPY METHODS
 Převorovský, Zdeněk ; Krofta, Josef ; Chlada, Milan
Facilities of nonlinear ultrasonic spectroscopy for defects detection in steel-reinforced concrete structures are discussed in the paper. Results are shown from non-destructive evaluation of concrete block samples reinforced with intact and corroded armature. Seven piezoelectric transducers were glued on the sample surface. One of them was used to harmonic excitation of the structure with frequency f1=45 kHz and stepwise growing amplitude. Among other 6 transducers one was multiplexed as a second transmitter of harmonic signal with f2=217 kHz and remaining sensors were receiving structural response on 2-frequency excitation. Most pronounced spectral differences between samples with corroded and intact reinforcement were observed on amplitude dependence of 3f1/2f1 ratio and f2-3f1 sidebands, which can be considered as nonlinear parameters characterizing concrete damage.
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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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FUZZY LOCATION OF ACOUSTIC EMISSION SOURCES IN CYCLICAL LOADED AIRCRAFT STRUCTURE
 Blaháček, Michal ; Převorovský, Zdeněk
There are many experiments and measurements, where typical AE source location error 100-1000 mm is clearly unacceptable. In suggested paper problem of AE source location accuracy increasing will be discussed. Method based on fuzzy sets theory principles will be demonstrated using AE data recorded during fatigue test of small aircraft landing gear bracket.
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Určení znaménka prvého nasazení a času příchodu u signálů akustické emise pomocí metody vyšších statistických momentů
 Lokajíček, Tomáš ; Klíma, Karel
Application of high order statistic to determine arrival time and sign of ultrasonic and acoustic emission signals.
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