Papers by Keyword: Acoustic Emission (AE)

Paper TitlePage

Authors: Mohd Muhridza Yaacob, Malik Abdulrazzaq Alsaedi
Abstract: The partial discharge (PD) phenomenon is very harmful for electrical appliances and its early detection could be a cost effective approach for the industry. Although many techniques are used for PD detection yet no technique has presented widely acceptable solution. Still the subject needs parallel study of the detection techniques. In this study, partial discharge signal has been captured by the three techniques using fiber optic sensor (FOS), Piezoelectric Sensor (PZT), leakage current (LC) techniques. In these experiments, FOS shows good sensitivity in the range of applied high voltage > 5 kV. The sensitivity and noise level of PD signal was different in these two experiments. The location of a PD was demonstrated in a 500 gallon water tank using convolution method.
316
Authors: Mohd Muhridza Yaacob, Malik Abdulrazzaq Alsaedi
Abstract: The partial discharge (PD) phenomenon is very harmful for electrical appliances and its early detection could be a cost effective approach for the industry. Although many techniques are used for PD detection yet no technique has presented widely acceptable solution. Still the subject needs parallel study of the detection techniques. In this study, partial discharge signal has been captured by the three techniques using fiber optic sensor (FOS), Piezoelectric Sensor (PZT), leakage current (LC) techniques. In these experiments, FOS shows good sensitivity in the range of applied high voltage > 5 kV. The sensitivity and noise level of PD signal was different in these two experiments.
277
Authors: Vladimir Dekýš, Peter Kopas, Milan Sapieta, Ondrej Stevka
Abstract: Change the deformation mechanism in metallic materials may be detectable using infrared thermography and acoustic emission. For samples of mild steel is the creation of Lüder’s bands presented in the infrared spectrum. Follow-number increase of these bands is also presented. In the system of acoustic emission is for this deformation mechanism described signal, which allows detection of the deformation process of these technologies.
315
Authors: Marek Vondra, Gabriel Cséfalvay, Petr Sedlak
Abstract: Acoustic emission (AE) is one of the most used nondestructive technique since it offers a great potential due to its ability of quantitative evaluation such as source location and source characterization. A common set of recorded acoustic emission signals has an extraordinarily wide dynamic range. Thus, the input gain of the A/D converter plays a key role due in information loss considering limitation of high signal amplitudes and domination of quantization noise at low levels. The usage of a logarithmic preamplifier extends the dynamic range of conventional A/D converters, thus increases the accuracy and signal-to-noise ratio of weak acoustic emission signals.
541
Authors: Ya Chun Dai, Jian Wei Xu, Dian Kai Huang, Jing Jing Zhang
Abstract: This paper was according to the early crack identification on metal deep drawing, combined with the characteristics of the AE singal of deep drawing forming, determined to analyze it by db4 wavelet basis function for 3 layers, extracted the energy value at every point of the eight AE signal samples from deep drawing forming which crack state was known to constituted characteristic matrix, fuzzy equivalence matrix was obtained by a series of matrix transformation,which was regard as pattern library of crack that used in cluster analysis. Then extracted energy value at every point of AE signal from deep drawing experiments with there states unknown, calculate similarity between samples and the model we established by using euclidean distance formula after normalization processing, deep drawing state was determined by the principle of selecting near, finally compared the recognition result with crack situation deviced by naked eye and microscope, results show that the accuracy of fuzzy identification of early crackn based on fuzzy clustering is up to 90%.
26
Authors: Andrew Spencer, Keith Worden, Gareth Pierce
Abstract: When a metal or composite structure begins to fail, for example due to high cycle fatigue, acoustic emissions caused by the propagation of cracks give rise to bursts of ultrasonic waves travelling through the structure. The health of a structure can be monitored by means of sensors which detect these waves. Acoustic emissions are often generated in experiments by breaking a pencil lead against the surface of the structure in a standardised way but the forces that this imparts are not well understood at present. A Local Interaction Simulation Approach (LISA) algorithm has been implemented to simulate the propagation of ultrasonic waves. This code has been validated against experiments in previous work and has been shown to accurately reproduce the propagation of Lamb waves (including reflections and dispersion etc.) within thin-plate like structures. This paper deals with the use of the LISA code to characterise the forces associated with standard pencil lead breaks. The displacement due to waves emanating from a break is measured and a Differential Evolution (DE) optimisation scheme is used to find the optimal profile of forcing to match the simulation with experiment.
793
Authors: Joanna Krajewska-Śpiewak, Józef Gawlik
Abstract: Under the influence of the pressure caused by the application of the cutting edge on the surface of the workpiece elastic waves are generated. Waves propagate in the material in every possible direction and can be identify by specialized measuring equipment. Acoustic emission phenomenon was used to determine the beginning of decohesion process. The article presents a new method for determination of the decohesion process during peripheral milling performed with the indexable cutting tools on samples made out of titanium based alloy and nickel based alloy.
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Authors: Zhong Ning Zhang, Jian Tian
Abstract: For the problem of acoustic emission source location, it has always been one of the important issues to look for simple and convenient layout of sensors. This paper presents a new time difference method for locating acoustic emission source in a plate, which the sensors for locating are arranged in a straight line, and does not need the pre-determining of the acoustic wave propagation velocity. The method makes the acoustic emission source locating task simplified.
561
Authors: Rhys Pullin, Pete T. Theobald, Karen M. Holford, S.L. Evans
Abstract: This paper reports on a method for numerically modelling acoustic emission signals in simple plate geometries using dispersion curves. It is demonstrated how, by using a known source to sensor distance, it is possible to determine the arrival of the frequencies of the individual AE modes at the sensor face. Assumptions based on sensor frequency response and the amplitude of individual modes allow for an approximation of each mode arriving at the sensor face. These modes are then summed to provide a numerical model of the expected signal. Results of the model are compared with a recorded signal and show good correlation, this is further demonstrated by comparing the wavelet transforms of the modelled and recorded signal.
381
Authors: Muhamad Bunnori Norazura, Rhys Pullin, Karen M. Holford, R.J. Lark
Abstract: Acoustic Emission (AE) testing in concrete structures shows great potential for monitoring and assessing the health condition of structures. Source location is normally based on the arrival times of transient signals, the simplest method is known as the Time of Arrival (TOA) method, where the location of the damage can be determined from the arrival time of the event at two or more sensors. When using this method, the wave velocity of the signals that propagate through the material needs to be determined. Homogenous materials, such as steel, have welldefined velocities, but in non-homogeneous materials such as concrete the wave velocity is more difficult to predict. This makes the use of a single wave velocity as required in the TOA method very difficult due to the variety of wave velocities obtained, especially for large structures. This paper explores wave propagation in concrete structures over a variety of source to sensor distances. Experiments were performed on a reinforced concrete beam and a reinforced concrete slab, using an Hsu-Nelsen (H-N) Source. It is found that, in general, as the source to sensor distance increases, the wave velocity decreases. The presence of longitudinal and transverse waves is demonstrated and the influence of the part of the waveform used for temporal measurement is explored. In order to provide a practical approach to velocity determination, different thresholds are investigated and the results are discussed in relation to the wave modes present.
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