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Condition monitoring of thrust ball bearings using continuous AE
Chlada, Milan ; Nohal, L. ; Převorovský, Zdeněk
Fast and reliable analysis of continuous AE recorded during endurance tests on flat washer parts reliably simulating critical rolling contact fatigue of the full-scale bearings is presented in the paper. Two channels of continuous AE signal were partially recorded within whole specimen lifetime tests and compared with other experimental parameters as vibration rate or temperature. As an alternative to classical spectrogram analysis, we proposed to use histograms of time intervals between threshold amplitudes crossings in various frequency bands represented by the wavelet decomposition. Results obtained on long-time records are discussed, illustrating advantages of proposed AE signal processing, which can be done in real time to observe the processes before the onset of the final damage on the surface of the specimen more precisely than vibrodiagnostics.
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Multilevel Analysis of Continuous Acoustic Emission Records
Chlada, Milan ; Převorovský, Zdeněk
The latest acoustic emission (AE) systems provide continuous recording of high-frequency signals registered during longtime monitoring of various processes in materials. Recorded data represent extremely large amount of information to analyze, however, it reflects the health of the structure. Therefore, in the last years the attention is paid to the diagnostic method of continuous AE also as a part of Structural Health Monitoring (SHM) systems. For example it can disclose the early damage phases (cracks) or certain imperfections in rotating gearboxes, the leakage of liquids from pressure vessels and many other material defects. This method requires new signal processing and analysis approaches, which are different from the burst AE. The paper deals with the analysis of continuous AE, recorded during the test of renovated gearbox at different flight modes. As an alternative to classical spectrogram, so-called multilevel countogram based on the signal wavelet decomposition is proposed and discussed.
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Utilising of position profiles for location of continuous acoustic emission sources
Chlada, Milan ; Převorovský, Zdeněk ; Sladký, Petr
By detecting of continuous acoustic emission (AE) sources it is possible to precede potential emergencies as e.g. leaks of the media from pressure vessels, pipelines etc. Present location methods using attenuation characteristics of elastic waves have certain application restrictions. These disadvantages can be solved by introduction of so called position profiles. In this way, the attenuation dependencies of AE wave amplitude and the distance from emission source are converted to the dependencies between position profiles and Root Mean Square (RMS) of captured voltage signals of continuous AE. Proper location of real AE source is done by comparing of position profiles corresponding to model virtual sources with the position profile computed for a real source, while it is possible to apply optimization comparative methods or artificial neural networks. The paper presents detailed derivation and description of the new method, which is a subject of patent pending.
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