Identification of impact force in thick plates based on the elastodynamics and time-frequency method (I) - Theoretical approach for identification the impact force based on elastodynamics

摘要

Determination of impact load is important for detecting and analyzing the flaws in thick plate. In industrial plants, thick aluminum plate is popularly used and impact load is identified by convolving the acoustic waveform, which is measured with sensors arrayed on the plate, and by Green's function, which is the transfer function between impacting position and sensor. In practical situations, it is difficult to measure Green's function. In this paper, the impact load on the plate is inversely recovered by using Green's function and the acoustic waveform. Green's function and the acoustic waveform are theoretically obtained based on the plate theory. There are three plate theories. One is the classic plate theory (CPT), which has been used for thin plate. The others are the exact plate theory and the approximated shear deformation theory (SDPT), which are used for the thick plate because the CPT overestimates the group velocity at high frequency in the thick plate. In this paper, the thick plate theory is used for the prediction of the acoustic waveform. This theoretical Green's function can be also used for the inverse problem of impact load based on the experimental method.