Browsing by Author "Archibald, Charles Mark"

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    Experimental determination of the impulse response function for elastic vibrating systems
    Archibald, Charles Mark (Virginia Tech, 1990-05-06)
    An experimental method for determination and analysis of the impulse response function of linear, elastic, vibrating systems is developed. A deconvolution method is developed for estimation of the impulse response function. The estimator is shown to be unbiased in the presence of measurement noise. Modal parameters are extracted from impulse response estimates using a modification of the Pisarenko harmonic decomposition method. The advantages of a time-domain approach over traditional Fourier analysis procedures, including avoidance of leakage and enhanced statistical significance, are described. Several tests used to determine the performance of the impulse response estimator are described, and the results of these tests, are presented. It is shown that the method can provide accurate estimates of modal parameters even for short data sets or high noise levels.
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    Parametric spatial modal analysis of beams
    Archibald, Charles Mark (Virginia Tech, 1993-07-04)
    Modal analysis is the experimental characterization of the dynanlical behavior of a structure. Recent advances in laser velocimetery have made available to the experimentalist a rich, new source of vibration data. Data can now be obtained from many different spatial locations on a structure. A method is presented to use this new data for the analysis of beams. Two approaches are investigated: minimum residual methods and boundary condition methods. The minimum residual approaches include autoregressive methods and non-linear least squares techniques. Significant contributions to sample rate considerations for parametric sinusoidal estimation resulted from this research. The minimum residual methods provide a good connection between the measured data and the fitted model. However, they do not yield a true modal decomposition of the spatial data. The boundary condition approach provides a complete modal model that is based on the spatial data and is completely compatible with classical beam theory. All theoretical constraints are included in the procedure. Monte Carlo investigations describe the statistical characteristics of the methods. Experiments using beams validate the methods presented. Advantages and limitations of each approach are discussed.