Deák, Tamás

Dobján, Tibor

Doszpod, László

Pletl, Szilveszter

Pór, Gábor

Dobján Tibor

Pletl Szilveszter

Deák Tamás

Doszpod László

Pór Gábor

University of Szeged

Identification of the Place and Materials of Knocking Objects inFlow Induced VibrationTibor Dobján, Szilveszter Pletl, Tamás Deák, László Doszpod, and Gábor PórMany industrial systems contain pipes with fluid flow in it, either for transmitting materialsor for cooling purposes. If some parts of the system detached or loosened it may go to eitherchaotic or deterministic motion due to forces gained from the flow energy. This motion iscalled flow induced vibration. If loose part knocks on the inner surface of the tube (or othercompartment) then audible knock is generated. These are surface waves on the metal surfaces.The place of the knocks and the knocking material are crucial from the point of view of thefate of the given industrial objects. Therefore identification of the event, finding its place andidentification of knocking material have primary importance form the point of view of thesafety and maintenance of the system.We investigated the improvement of the identification of the event recognition using autore-gressive modeling based filtering [1] and sequential probability ratio test. While some parts ofthis technique had been elaborated earlier, the realization of those algorithms in LABVIEW andits integration into an embedded system are brand new developments.For the localization of the place of the event, we investigated basically the time delay esti-mation methods. Time delays were estimated using cross-correlation technique and impulseresponse estimation. From the estimated time delays using linear measures of the piping sys-tem one can conclude the place of the knocks. However, besides the direct effect, i.e. besidesthe shortest route of the sound there are several other routes, reflections in the system, which inthe case of repeated knocks can overlap with the arriving new front of the subsequent knocks.Selection of the arriving front were based on the physical nature of different fronts, however,this required an intelligent programming technique.To give a hint on the material of the knocking objects we estimate the auto power spectraldensity function by dividing the frequency band into high frequency part and low frequencypart. It was shown, that the ratio of these partial RMS values are different for knocking objectof different materials. We present the first results of division of the APSD into four parts. It canbe clearly seen, that this may improve the identification.Finally, we discuss the possibility of introduction of neural network techniques into theprocess of identification of the place and material of knocking objects.References[1] George E. P. BOX, Gwilym M. Jenkins: TIME SERIES ANALISIS forecasting and control,Holden-Day, 197629

Identification of the place and materials of knocking objects in flow induced vibration : [abstract]

http://acta.bibl.u-szeged.hu/59956/1/cscs_2010_029.pdf

Identification of the place and materials of knocking objects in flow induced vibration

Identification of the place and materials of knocking objects in flow induced vibration

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University of Szeged