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Modal testing

About: Modal testing is a research topic. Over the lifetime, 4047 publications have been published within this topic receiving 64772 citations.


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Journal ArticleDOI
TL;DR: The results of this study indicate that the four-node support can be used in free vibration test to determine the elastic properties of full-sized WCPs.
Abstract: Key elastic properties of full-sized wood composite panels (WCPs) must be accurately determined not only for safety, but also serviceability demands. In this study, the modal parameters of full-sized WCPs supported on four nodes were analyzed for determining the modulus of elasticity (E) in both major and minor axes, as well as the in-plane shear modulus of panels by using a vibration testing method. The experimental modal analysis was conducted on three full-sized medium-density fiberboard (MDF) and three full-sized particleboard (PB) panels of three different thicknesses (12, 15, and 18 mm). The natural frequencies and mode shapes of the first nine modes of vibration were determined. Results from experimental modal testing were compared with the results of a theoretical modal analysis. A sensitivity analysis was performed to identify the sensitive modes for calculating E (major axis: Ex and minor axis: Ey) and the in-plane shear modulus (Gxy) of the panels. Mode shapes of the MDF and PB panels obtained from modal testing are in a good agreement with those from theoretical modal analyses. A strong linear relationship exists between the measured natural frequencies and the calculated frequencies. The frequencies of modes (2, 0), (0, 2), and (2, 1) under the four-node support condition were determined as the characteristic frequencies for calculation of Ex, Ey, and Gxy of full-sized WCPs. The results of this study indicate that the four-node support can be used in free vibration test to determine the elastic properties of full-sized WCPs.

15 citations

Proceedings ArticleDOI
01 Jan 1983
TL;DR: In this paper, a new testing technique and the Ibrahim time-domain (ITD) modal identification algorithm have been combined, resulting in a capability to estimate modal parameters for rotating-blade systems.
Abstract: A new testing technique and the Ibrahim time-domain (ITD) modal identification algorithm have been combined, resulting in a capability to estimate modal parameters for rotating-blade systems. This capability has been evaluated on the Sandia two-meter, vertical-axis wind turbine. Variation in modal frequencies as a function of rotation speed has been experimentally determined from 0 rpm (parked) to 800 rpm. Excitation of the rotating turbine was provided by a scheme which suddenly released a pretensioned cable, thus plucking the turbine as it rotated. The structural response was obtained by passing the signals through slip rings. Using the measured free-decay responses as input data for the ITD algorithm, the modes of the rotating turbine were determined at seven rotation speeds. The measured modal parameters were compared with analytical results obtained from a finite element analysis and with experimental results obtained from a complex exponential identification algorithm.

15 citations

Proceedings ArticleDOI
01 Jan 1986
TL;DR: In this article, four methods for the calculation of derivatives of vibration mode shapes (eigenvectors) with respect to design parameters are reviewed and compared, and the amount of central processor time used to compute the first four eigenvector derivatives for each example problem; errors and rapidity of convergence of the approximate derivative to the exact derivative are taken into account.
Abstract: Four methods for the calculation of derivatives of vibration mode shapes (eigenvectors) with respect to design parameters are reviewed and compared. These methods (finite difference method, Nelson's method, modal method and a modified modal method) are implemented in a general-purpose commercial finite element program and applied to a cantilever beam and a stiffened cylinder with a cutout. A beam tip mass, a beam root height and specific dimensions of the cylinder model comprise the design variables. Data are presented showing the amount of central processor time used to compute the first four eigenvector derivatives for each example problem; errors and rapidity of convergence of the approximate derivative to the exact derivative are taken into account. Nelson's method proved to be most reliable and efficient.

15 citations

Journal ArticleDOI
TL;DR: In this article, a recently built curved twin-deck cable-stayed footbridge was analyzed, whose structural complexity required wind tunnel tests and a specific design for vibration reduction, in order to meet wind safety requirements owing to premature aeroelastic instability, and mitigate pedestrian vibrations.
Abstract: The article focuses on dynamic identification strategies for complex bridge structures equipped with passive vibration control systems. In detail, a recently built curved twin-deck cable-stayed footbridge was analysed, whose structural complexity required wind tunnel tests and a specific design for vibration reduction. A passive control system was deemed necessary in order to: (i) meet wind safety requirements owing to premature aeroelastic instability, and (ii) mitigate pedestrian vibrations. Uncertainties in numerical modelling and changes during its construction suggested a modal testing campaign in order to check the effectiveness of the vibration absorption system. Different excitation sources related to output-only techniques were exploited, including ambient noise and free-decay oscillations through released masses. Several sensor set-ups were deemed necessary in the view of the structure complexity that exhibits numerous close modes and modal couplings between the two decks. The effect of the dampers was analysed by performing the testing campaign for two distinct configurations: (i) disconnected dampers, and (ii) connected dampers. The dynamic properties of the cables were also investigated in order to complete the whole dynamic characterization of the structure. Two time-domain techniques were applied and compared under different excitations. The dynamic identification procedure provided consistent results and highlighted that full functionality of the damping system was realized only for high vibration levels. Finally, time-frequency instantaneous estimators were applied in order to analyse both the modal frequency and the damping time-variation. These results revealed amplitude dependent behaviours as well as dynamic deck-cable interactions

15 citations

Journal ArticleDOI
TL;DR: The simulation results of mass time-varying three-degree-of-freedom (DOF) and cantilever beam prove that this new method can identify the modal shapes and natural frequencies of LTV structure only from non-stationary vibration response signals and the performance of identification is much better than moving window independent component analysis (ICA).

15 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202367
2022164
202141
202059
201967
201878