Wyniki wyszukiwania - BazTech

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Analiza częstotliwościowa odpowiedzi akustycznej wzbudzanej mechanicznie płyty stalowej

Dobrzycki A., Knitter-Piątkowska A.

Poznan University of Technology Academic Journals. Electrical Engineering

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2018

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No. 93

323--334

PL

W przypadku konstrukcji budowlanych niezbędna jest wiedza o stanie ich poszczególnych elementów, w szczególności w miejscach narażonych duże obciążenia. Znajomość tego stanu ma bezpośredni wpływ na bezpieczeństwo użytkowania tychże. Powyższy powód jest przyczynkiem do opracowywania nowych i udoskonalania istniejących metod diagnostycznych. Szczególnie wartościowe są te metody, które pozwalają na wykonanie diagnostyki w sposób bezinwazyjny (nie wymagający wyłączenia obiektu z użytku na czas pomiaru). W artykule przedstawiono wyniki wstępnych badań nad możliwościami wykorzystania metody akustycznej w analizie stanu metalowych konstrukcji budowlanych. Przedstawiono koncepcję pomiarową, zbudowane stanowisko pomiarowe oraz sposób prowadzenia pomiarów. Ponadto zaprezentowano wyniki badań wstępnych, mających na celu wskazanie w widmie zarejestrowanych sygnałów częstotliwości dominujących. Zbadano wpływ podłoża, na którym umieszczano płytę oraz liczbę i rodzaj uszkodzeń na widmo zarejestrowanych sygnałów akustycznych.

EN

In the case of building structures, it is necessary to know the status of their individual elements, in particular in places subject to high loads. Knowledge of this state has a direct impact on the safety of using these. The above reason is a contribution to developing new and improving existing diagnostic methods. The methods that allow noninvasive diagnostics (which does not require excluding the object from use during the measurement period) are particularly valuable. The article presents the results of preliminary research on the possibilities of using the acoustic method in the analysis of the condition of metal building constructions. The measurement concept, the built-in measuring stand and the way of carrying out the measurements are presented. In addition, the results of preliminary tests to show the recorded signals of dominant frequencies in the spectrum have been presented. The influence of the substrate on which the plate was placed and the number and type of damage to the spectrum of recorded acoustic signals were investigated.

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Selected problems of damage detection in internally supported plates using one-dimensional Discrete Wavelet Transform

Guminiak M., Knitter-Piątkowska A.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 3

631--644

EN

The paper is concerned with damage detection in plates while using the Discrete Wavelet Transform (DWT). Rectangular plate structures resting on a Winkler or elastic half-space type foundation, with free boundaries are examined. Plate bending is described and solved by the Boundary Element Method in a direct approach. Defects are introduced by additional edges forming slots in relation to the basic plate domain. Numerical investigation is conducted basing on signal analysis of the structural static response and by taking advantage of multi-resolution analysis (MRA) of the signal function which can be represented in a multi-scale manner. The obtained signal is decomposed with the use of Daubechies or Coiﬂet wavelet families. The white noise generator is used to model measurement inaccuracy which is an inevitable element of a real experiment. The eﬃciency of DWT of the contaminated signal in damage detection is studied.

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Crack identification in plates using 1-D Discrete Wavelet Transform

Knitter-Piątkowska A., Guminiak M., Hloupis G.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 2

481--496

EN

In the present work, the defect detection while using Discrete Wavelet Transform in rectangular plate structures is investigated. The plate bending is described by using the Boundary Element Method with boundary integral equations formulated in a modified simplified approach. The boundary elements of a constant type in a non-singular approach are implemented. Defects are introduced by additional edges forming slots or holes in relation to the basic plate domain. Estimation of the defect position is performed while using wavelet coefficients of curvature and deformation signals as well as a newly proposed moving variance estimator.

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Defect detection in plate structures using wavelet transformation

Knitter-Piątkowska A., Guminiak M.

Engineering Transactions

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2016

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Vol. 64, iss. 2

139--156

EN

This paper is concerned with defect detection in plate structures while considering the influence of external loads. The examined structures are based on Kirchhoff plate structures. Rectangular plate structures are considered. Plate bending is described using the boundary element method. The boundary and boundary-domain integral equations are formulated in a modified, simplified approach without the need of using a value known from the classical theory of Kirchhoff plate bending. Constant-type boundary elements in a non-singular approach are introduced. The plates are loaded with a single static concentrated force or dynamic moving force. External loading is applied at selected points along the direction parallel to one dimension of the plate. Defects are introduced by additional edges forming slots or holes in relation to the basic plate domain. Deflections and curvatures are taken into account as structural responses. Analysis of structural responses is conducted using the signal processing tool of wavelet transformation in its discrete form.

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Application of discrete wavelet transformation to defect detection in truss structures with rigidly connected bars

Knitter-Piątkowska A., Guminiak M., Przychodzki M.

Engineering Transactions

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2016

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Vol. 64, iss. 2

157--170

EN

The structures examined in this paper are bridge-type trusses that were previously used as railway viaduct support structures. The considered trusses are modelled as 2D and 3D structures. The lower chord bar of the considered structure can be loaded by external forces located outside the rigid nodes (the points where truss bars are connected). Hence, in the numerical experiment in terms of 2D approach, the truss structure consists of the set of two-node beam finite elements with three degrees of freedom per node and exact shape functions. According to 3D approach, the truss is described as the set of two-node beam elements with six degrees of freedom per node. Axial and twisting displacements of the element are described by linear shape functions and the bending is described by polynomials of the third order corresponding to Euler-Bernoulli beam fields of deformation. The defect (damage) in truss structure is modelled as the local stiffness reduction of one or two lower chord bars. The analysis of a structural response is carried out using the discrete wavelet transformation (DWT). The aim if this work is to detect the localization of damage provided that it exists in the considered structure and to examine whether the DWT will prove to be the effective tool to defect detection. It is expected that the disturbance of the response signal will appear in the vicinity of the point where the defect exists. The family of Daubechies 4 wavelet is implemented. Numerical investigation is executed based on signal analysis of structural static response. Some numerical examples are presented.

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Application of discrete wavelet transformation in damage detection. Part I: Static and dynamic experiments

Knitter-Piątkowska A., Pozorski Z., Garstecki A.

Computer Assisted Mechanics and Engineering Sciences

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2006

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Vol. 13, No. 1

21-38

EN

The paper demonstrates the potential of Discrete Wavelet Transform (DWT) in damage detection. Efficiency of the method is demonstrated by the way of examples. In this study the numerically simulated static and dynamic experiments were used. One dimensional DWT was used to signal processing. Measurement errors were accounted for by introduction of white noise.