The Echo Characteristic Of Plate Coating With Damping Layer And Elastic Parameter Inversion

Target echo characteristics and elastic parameters inversion were performed in the theory and experiment in the thesis. The theory research is as follows: firstly, based on the wave equation in plates, dispersion equations of Lamb propagation were derived respectively under 6 kinds of boundary conditions, including in vacuum, in water, covered with water, covered with damping layer in vacuum or water. Secondly, the numerical solutions of dispersion equations were solved and the dispersion curves were plotted. The results were analyzed, and these physics meanings were given. At last, the rectangle plate echo characteristic was analyzed under the oblique incidence condition. And known Lamb's phase velocity in plate, the elastic parameters of plate were inversed by using Genetic Algorithm (GA) toolbox of the Matlab. In the experimental research, the target echo characteristics experiment was done with four models (two armor plates with different size, one aluminum alloy plate and one elastic plate covered with damping layer). With changing the target azimuth, when strong echo coming out, angles were observed and the data was recorded. Then the echo structure was analyzed. And based on the formulas in the theory, the phase velocity was calculated. So, platelike materials' elastic parameters were inversed. The theoretical derivation is validated by experimental results. And the method of elastic parameters inversion that is the combination of underwater target echo characteristics and GA is feasible.