15 Investigation of Notch-Type Damage Identification by Using a Continuously Scanning Laser Doppler Vibrometer System 145 Fig. 15.1 CSLDV system developed in this work Fig. 15.2 (a) Dimensions of a damaged aluminum beam and the notch location with respect to a scan line, (b) details of the notch, and (c) the experimental setup to obtain ODSs of the beam by the CSLDV system CSLDV system is used to measure the velocity response of the beam along the scan line. The sampling frequency of the CSLDV system is 50,000 Hz in this work. In the following description, a scan line is nondimensionalized to range from0% to100%, where 0%and 100% represent left and right ends of the scan line, respectively. 15.2.1.1 Demodulation Method The steady-state response frequency of a linear time-invariant structure that results from sinusoidal excitation is equal to the excitation frequency. When using the CSLDV system to measure the velocity response of the beam in Fig. 15.2c, the laser
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