An Experimental System for Measuring the Wavenumber-Frequency Response of Timoshenko Beams
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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The wavenumber-frequency response of Timoshenko beams to multiple point drives is studied in this thesis. An experimental system to excite a free- free Timoshenko beam and measure the resulting velocity is developed. Piezoelectric shakersforce gate units are designed and built to excite the beam and measure the applied forces. Experiments varying the number of shakers used and the wavenumber to which the drive voltage sent to the shakers used and the wavenumber to which the drive voltage sent to the shakers is steered are performed. The wavenumber-frequency dependence of the force and velocity are measured and compared to theoretical predictions. These comparisons show excellent agreement between the measured and theoretical results. A theoretical investigation into the effect of the velocity measurement array is performed. Also, the finite beam admittance is examined. The piezoelectric shakers are modeled using equivalent circuits, which successfully predict the force output and the force gage sensitivity. The experiments show that the wavenumber content of the discrete shakers could be steered to the wavenumbers chosen over a wide frequency range the frequency range of measurement was 2-12 kHz. The finite beam admittance is shown to approach the infinite beam admittance in regions where the wavenumber content of the forcing function are high.