https://hal.inria.fr/hal-01021054Flynn, Eric B.Eric B.FlynnLANL - Los Alamos National LaboratoryEmbedded Multi-Tone Ultrasonic Excitation and Continuous-Scanning Laser Doppler Vibrometry for Rapid and Remote Imaging of Structural DefectsHAL CCSD2014Signal processingUltrasonic for (seismicacoustic) methodsSensor systems and networks[PHYS.MECA] Physics [physics]/Mechanics [physics][SPI.MECA] Engineering Sciences [physics]/Mechanics [physics.med-ph][MATH.MATH-ST] Mathematics [math]/Statistics [math.ST][STAT.TH] Statistics [stat]/Statistics Theory [stat.TH]Jaigu, AnneLe Cam, Vincent and Mevel, Laurent and Schoefs, Franck2014-07-09 08:43:182014-07-09 15:29:042014-07-09 15:29:04enConference papersapplication/pdf1We describe a novel method for rapidly measuring local wave dispersion properties using steady-state excitation continuous-scanning laser Doppler vibrometery (CSLDV). In our approach, we excite a structure with a periodic ultrasonic waveform constructed from the sum of several single-tone waveforms. The structure is excited continuously, bringing it to steady-state. We then measure the steady-state response of the structure through CLSDV. The continuous scan gives a one-dimensional time-history of measured response velocity, which we convert to time histories of the instantaneous amplitude and phase for each excitation frequency component. We then map these instantaneous amplitudes and phases to a discretized grid of points spanning the scan area. Finally, through wavenumber processing, we convert these 2D maps into local estimates of wavenumber. Since this is done for each excitation frequency, we are left with a set of frequency samples of local frequency-wavenumber dispersion curves at each spatial sample point in the structure. Since defects alter local dispersion properties in a predictable way, these dispersion curve maps offer an effective means of both locating and characterizing defects such as corrosion and delamination.