Wykorzystanie sygnału wibroakustycznego w diagnostyce struktur sprężonych

Krzysztof Szczurowski

Abstract

The dissertation presents evaluation of technical condition of a pre-stressed structure while in particular underscoring the possibilities of exploiting the effects of amplitude modulation occurring in the observed vibroacoustic signal. The basis of such an approach is the main thesis of the dissertation, i.e. “The change in the distribution of stress in the cross-section of a pre-stressed structure is accompanied by a measurable change of a vibroacoustic signal’s parameters.” It is the outcome of the assumption that occurrence of pre-stressing in a bent structure is accompanied by a phenomenon of dispersion and hence also by the change of parameters of wave propagation, especially the occurrence of a measurable difference between the values of phase and group velocity. Analysis of the relations between the state of stress and the values of phase and group velocity creates the possibility of building inwerse diagnostic models and thus determining quantitative changes of such parameters of the technical condition as pre-stressing forces, Young’s module or stress in the structure. The first chapter presents the review of the methods which are currently used in the task of assessing the technical condition of prestressed structures while presenting the scope and the limitations of their application. The next two chapters discuss modeling and examination of homogenous materials on the basis of an example of an externally stressed steel plate. The results of simulations, performed with the use of FEM method, are presented along with the analyses of the dynamic response of the plate which is installed in a laboratory test-bed. Chapter four contains the models waves propagation in structures built of homogenous materials along with the quoted results of analyses of signals registered during laboratory tests. The following chapters present physical models which describe the dispersion phenomenon and its influence on the changes occurring in the vibroacoustic signal, results of analyses of signals obtained during examination of structures conducted with various degree of pre-stressing as well as with introduced, exemplary defects. The results presented in the seventh chapter confirm the correctness of the thesis of the dissertation while the presented results of verification of models by means of experiments allow determination of the conditions and the scope of their application. The last chapter, while referring to the results of research being part of the dissertation, proposes the dispersion diagnostic model along with a proposal of an algorithm of the diagnostic-prognostic inference.
Diploma typeDoctor of Philosophy
Author Krzysztof Szczurowski
Krzysztof Szczurowski,,
-
Title in PolishWykorzystanie sygnału wibroakustycznego w diagnostyce struktur sprężonych
Languagepl polski
Certifying UnitFaculty of Automotive and Construction Machinery Engineering (FACME)
Disciplinemechanical engineering / (technology domain) / (technological sciences)
Defense Date21-01-2010
End date24-02-2010
Supervisor Stanisław Radkowski (FACME / IAE)
Stanisław Radkowski,,
- Institute of Automotive Engineering

Internal reviewers Zbigniew Dąbrowsiki (FACME / IMDF)
Zbigniew Dąbrowsiki,,
- Institute of Machine Design Fundamentals
External reviewers Czesław Cempel
Czesław Cempel,,
-
Pages131
Keywords in Englishxxx
Abstract in EnglishThe dissertation presents evaluation of technical condition of a pre-stressed structure while in particular underscoring the possibilities of exploiting the effects of amplitude modulation occurring in the observed vibroacoustic signal. The basis of such an approach is the main thesis of the dissertation, i.e. “The change in the distribution of stress in the cross-section of a pre-stressed structure is accompanied by a measurable change of a vibroacoustic signal’s parameters.” It is the outcome of the assumption that occurrence of pre-stressing in a bent structure is accompanied by a phenomenon of dispersion and hence also by the change of parameters of wave propagation, especially the occurrence of a measurable difference between the values of phase and group velocity. Analysis of the relations between the state of stress and the values of phase and group velocity creates the possibility of building inwerse diagnostic models and thus determining quantitative changes of such parameters of the technical condition as pre-stressing forces, Young’s module or stress in the structure. The first chapter presents the review of the methods which are currently used in the task of assessing the technical condition of prestressed structures while presenting the scope and the limitations of their application. The next two chapters discuss modeling and examination of homogenous materials on the basis of an example of an externally stressed steel plate. The results of simulations, performed with the use of FEM method, are presented along with the analyses of the dynamic response of the plate which is installed in a laboratory test-bed. Chapter four contains the models waves propagation in structures built of homogenous materials along with the quoted results of analyses of signals registered during laboratory tests. The following chapters present physical models which describe the dispersion phenomenon and its influence on the changes occurring in the vibroacoustic signal, results of analyses of signals obtained during examination of structures conducted with various degree of pre-stressing as well as with introduced, exemplary defects. The results presented in the seventh chapter confirm the correctness of the thesis of the dissertation while the presented results of verification of models by means of experiments allow determination of the conditions and the scope of their application. The last chapter, while referring to the results of research being part of the dissertation, proposes the dispersion diagnostic model along with a proposal of an algorithm of the diagnostic-prognostic inference.
Thesis file
Szczurowski.pdf 9.64 MB
Citation count*5 (2020-09-18)

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