Time, Wavelet and Hilbert-Huang Domain Analysis of Signals from Ultrasonic Based Equipment for the Non Destructive Evaluation of Concrete and Brick Masonry Walls
ABSTRACT In this paper we compare the effectiveness of the time, wavelet and Hilbert-Huang domain analysis of waveforms from a Non
Destructive Test (NDT) equipment. The analysis of the signals from NDT systems is one of the most important activities in
the recognition of the presence of possible defects that are usually associated with the presence of echoes from the defects
themselves. Very often the echoes traveling back to the sensors are superimposed with the signal from the transducer. We analyze
the waveforms obtained by couples of sensors in order to extract the echoes and to recognize the points were they originate.
Data are obtained by a measurement campaign on a concrete wall and on masonry specimens of different texture and thickness.
- "Sonic and ultrasonic techniques belong to non destructive testing (NDT) methods, which are particularly successful for industrial diagnostics and condition monitoring   . "
Conference Paper: Optimization of the set of path-rays in linear tomography[Show abstract] [Hide abstract]
ABSTRACT: In this work a new formalization of selecting the optimal set of path-rays problem in linear tomography is presented. In particular the problem of selecting the optimal set of path-rays is formalized as a problem of selecting a sub-matrix of a matrix with certain spectral properties, which is known to be an NP-hard problem. New criteria of optimality of the set of path-rays are introduced, and an optimization algorithm is proposed to deal with the combinatory search problem. The obtained results are compared to those of existing approximation algorithms. Numerical results show that the optimal solutions yielded by the proposed optimization algorithm, outperform existing algorithms in terms of conditioning of the tomography linear equations system.Digital Signal Processing (DSP), 2013 18th International Conference on; 01/2013
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ABSTRACT: A time-frequency analysis method based on Hilbert-Huang transform (HHT) was employed to character ultrasonic flaw echo signals. In this method, time and frequency characteristics of ultrasonic transducers used in inspection were considered to eliminate noises and identify the flaws. First, the flaw echo signals were decomposed into a series of mono-components called intrinsic mode functions (IMF) using the theories of EMD. Secondly, the best IMF was identified and represented in time-frequency domain using Hilbert transform, time and frequency characteristics were used to determine the flaw. Finally, the addition of the best IMF and the hypo-best IMF comes close to approximating the original flaw signal. The results of experiments with three transducers validate the effectiveness of the method in ultrasonic echo signal analysis.
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ABSTRACT: Concrete structures require periodic inspections and quality control to assess their structural integrity. For this task, several methodologies based on the use of different technologies have been previously proposed. In particular, nondestructive evaluations, based on the use of ultrasonic wave propagation, have proved to be attractive due to the possibility to perform reliable assessments of concrete structures. In this paper, an approach exploiting ultrasonic propagation characteristics is proposed. This approach is developed by using data obtained from numerical simulations, whereas proper simulation settings to perform the diagnosis are obtained by preliminary studies. Subsequently, an automatic inspection method to determine the position of defects is developed. The aim of the method consists of determining the position of a defect by the computation of flight times related to signals reflected by anomalies in the structure. Such computation is based on a preliminary classification of defect positions that combines a genetic algorithm for a feature selection and a statistical approach for classification. The performances of the proposed method are evaluated in a specific study case, showing satisfactory numerical results, which show that this approach can be used to identify the position of defects.Nondestructive Testing And Evaluation 12/2010; 25(4):289-315. DOI:10.1080/10589751003658057 · 0.63 Impact Factor