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Using Hilbert Huang transformation for analysis of non-stationary signals from physical experiments
Tuleja, Peter ; Balík, Miroslav (referee) ; Rášo, Ondřej (advisor)
This paper discusses the possible use of Hilbert-Huang transform to analyze the data obtained from physical experiments. Specifically for the analysis of acoustic emission in the form of acoustic shock. The introductory section explains the concept of acoustic emission and its detection process. Subsequently are discussed methods for signal analysis in time-frequency domain. Specifically, short-term Fourier transform, Wavelet transform, Hilbert transform and Hilbert-Huang transform. The final part contains the proposed method for measuring the performance and accuracy of different approaches.
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Application of electromagnetic and acoustic emission signals for localization of cracks generated during mechanical stressing of solids
Burděj, Václav ; Sadovský, Petr (referee) ; Koktavý, Pavel (advisor)
Terms of acoustic emission (AE) and electromagnetic emission (EME) designated physical effects and also as diagnostic methods based on these effects. These effects are caused by generated cracks in materials that rank among non-destructive techniques of material diagnostics. The advantage of them is that they do not affect the measured object and give us information about the current dynamic state of a tested material. One disadvantage of these effects is that they provide very low energy of signal emissions and make it difficult for broader usage. It is expected better localization of cracks in non-conductive materials by connecting of these two techniques (diagnostics). There are designed and described new methods for crack detection with usage of AE and EME signals in this work. Also there is description of measuring arrangement intended of crack detection and experimental sample for checking accuracy of methods for crack detection. There was performed comparison of accuracy of methods in crack detection.
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Non-destructive inspection methods of aircraft selected parts
Kníř, Jakub ; Třetina, Karel (referee) ; Trefilová, Helena (advisor)
Non-destructive testing (NDT) is a broad scientific field. This bachelor thesis provides an insight into NDT’s methods. It can’t embrace the whole field in any case because it’s needed to have knowledge from variety of other scientific fields in order to understand NDT completely. This thesis outlines basic testing methods and their usage for particular components of aircrafts. The thesis also includes a list of Czech and European standards relevant to the topic.
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Correlation of AE Signal Changes to Rolling Contact Damage Propagation
Nohál, Libor ; Čermák, Jan (referee) ; Hájek, Karel (referee) ; Hutař, Pavel (referee) ; Mazal, Pavel (advisor)
This PhD thesis deals with the experimental study of more precise rolling contact fatigue damage detection using acoustic emission method. A series of experiments was carried out on two representatives bearing steels and the analysis of sensitivity for the presence of contact damage was performed on selected parameters of acoustic emission. The extent of damage was classified into four classes and signal parameters the most characterizing the development of damage were correlated with the extent of damage. It was also verified the influence of lubricants on acoustic emission signals. The results have an impact on the implementation of more precise rolling contact fatigue tests and evaluation of parameters of acoustic emission signal. On the basis of experiments was established methodology for more precise RCF testing method using acoustic emission on test-rig AXMAT II.
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Vibration and impact measurement for collision analysis
Andruška, Martin ; Hrubý, Lukáš (referee) ; Musil, Tomáš (advisor)
This bachelor’s thesis deals with the issue of CubeSat collision and detection with microscopic particles of space debris and meteoroids. The aim of the thesis is to approach methods of detection, to describe various sensors for measurement of acoustic emission, shock and vibrations caused by collisions and by experimental comparison determine the suitability of their application. The thesis also contains description of possible methods of data analysis using amplitude and spectral analysis. Finally, there is a suggestion and realization of a possible way of processing acquired data from a sensor using an FPGA.
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Design and verification of station for calibration of AE sensors for bearing testing
Bančák, Matej ; Mazůrek, Ivan (referee) ; Mazal, Pavel (advisor)
The diploma thesis deals with calibration of AE sensors used in diagnostics of bearings. Two different conceptual solutions similar to those used in the diagnostics of bearings were designed in the design. Subsequently, the experimental device was designed for relative calibration using the rotation of bearings as a continuous AE source. The experimental part is oriented to the observation of the RMS parameter, which serves as a sensor sensitivity evaluation parameter. As sources of AE, bearings with a certain type of damage were used, which allowed for the formation of sensitivity characteristics according to the type of damage. Sensitivity characteristics of selected AE sensors have been developed to determine the effectiveness in relative calibration. The exponential sensitivity sensitivity of the MDK-13 sensors was observed on the software amplification of the AE analyzer. A proposal for the calibration method for MDK-13 type sensors was developed on the principle of comparison with the reference sensor.
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APPLICATION OF ACOUSTIC EMISSION METHOD FOR MORE DETAILED DIAGNOSTICS OF RADIAL BEARINGS DAMAGE
Hort, Filip ; Pazdera, Luboš (referee) ; Hájek, Karel (referee) ; Samek,, Jiří (referee) ; Mazal, Pavel (advisor)
This thesis studies the possibilities of exploiting the acoustic emission method as a tool for more detailed identification of the radial bearings damage formation. The work includes comparison of different evaluation methods in laboratory tests. Applied couplant between the contact sensor areas and sensing surfaces is also taken into account. The practical part includes the presentation of the experimental station and structural adjustments made. The main part of the work comprises the examples in detail of three types of experimental tests that simulate the possible failure of bearings and their manifestation in the sensing signal. Testing methodology developed with recommended values for setting common AE signal measurement, vibration and temperature is a part of the thesis, too.
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Acoustic emission signal classification at cyclic loading of parts
Stein, Pavel ; Mazůrek, Ivan (referee) ; Mazal, Pavel (advisor)
This master’s thesis is concerned analysis of signal of acoustic emission. The analysis is based on data of bearing material and real bearings testing, tested in the Axmat stands. The data was run by software Matlab and Python. Below I created plan for identification of damage stage depending on particular AE events. The results are put into diagram. Finally I’m trying to develop the new possibilities of using acoustic emission into practice on the real machines. There could be earlier prediction of a defect of monitored bearings compared to vibrating diagnostic used until now.
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Use of cold kinetic deposition technology on materials used in electrical engineering
Sámel, Maroš ; Zimáková, Jana (referee) ; Binar, Tomáš (advisor)
The purpose of this diploma thesis is to get a better understanding of cold kinetic deposition (cold spray), principles of functioning of this method followed by an evaluation of advantages and disadvantages of cold spray and its comparison to conventional thermal methods and a simple summary of the practical use of cold spray with respect to different materials. Next there is a summary of the properties and uses of frequently applied metals in electrical engineering, aluminium and copper, description of metal corrosion and an understanding of the diagnostic method of acoustic emission. In the practical part, a sample with copper cold spray coating on aluminium substrate was created. Following, this sample was split for corrosion tests, where the split samples were exposed to a corrosive environment for different times of exposure. The extent of corrosion degradation of the samples was evaluated by acoustic emission and metallographic analysis for corrosion-loaded samples for 100, 200 and 300 hours. In the end, an illustrative design of the application of the cold spray technology was created.
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Optimization of ultrasonic leak detector of pneumatic system
Macků, Ondřej ; Mazal, Pavel (referee) ; Vlašic, František (advisor)
The thesis deals with design and optimization of exchangeable modules for localization of air distributable ultrasound in concept of ultrasound probe design. Several series of these modules were manufactured using the technology of rapid prototyping and tested on artificially created source of air leak. Based on these verification experiments two types covering wide use for identification of pneumatic systems leaks were selected and modified. These two types are long range module for more accurate and expended reach of the leak detection and focusing attachment for narrowing the received range of scanning module and elimination of surrounding ultrasound. Part of the thesis is also analysis of the acoustic signal processed by modern acoustic emission analysers which allow besides standard parameters recording also continuous sampling up to 10 MHz and design solution for attachment of add-on modules to the detector. The thesis is beneficial for raising awareness of leak measurements, prototype manufacturing by using the 3D printing and designing and manufacturing of modules.
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