Sang-Kwon Lee
The Journal of Mechanical Science and Technology, vol. 22, no. 7, pp.1359-1373, 2008

Abstract : The paper presents a novel experimental method for the determination of the impact load in the thick plate based on the theoretical Green’s function and the measured waveforms by the sensors arrayed on the surface on the plate. This method requires the location of the impact load. For the accurate estimation of location of impact source in a plate, the arriving time difference between sensors and the propagation velocity of acoustic waveform are necessary. Their measurements are difficult since the acoustic waveforms are dispersive with multi modes in the plate. The time frequency analysis for the acoustic waveform gives the information about the time difference for multi mode dispersive waveform. For the estimation of location of impact source in a plate, the information on the group velocity of the A0 flexible mode is important. In the paper, various time frequency methods are introduced and their methods are compared with simulated signals. The combined higher order time frequency (CHOTF) is employed for dispersive information for the A0 mode flexible mode. The location of impact source and the magnitude of impact load are well estimated based on the theoretical Green’s function and the CHOTF for the acoustic waveforms measured by three sensors arrayed on the plate.

Keyword : Green function; Flexible wave; Force identification; Group velocity plate