The Simulation And Experimental Of Lamb Wave In Double Layer Bonded Thin Plate

Rubber materials has been widely used in transportation,aerospace and other fields for the excellent physical properties such as high acoustic attenuation,insulation and heat insulation.However,under the comprehensive effect of internal and external environment,the physical and elastic properties of rubber materials is prone to decay of,that is,aging.Therefore,how to detect the change of physical and elastic properties of rubber materials as soon as possible is a hot issue in the field of nondestructive testing.Based on this,this paper will make use of the characteristics of Lamb waves,such as high penetration and strong sensitivity to defects,to carry out a preliminary study on the elastic properties of non-metallic double-layer materials.In this paper,the influence of the elastic properties of bimetal materials on the dispersion characteristics of Lamb waves is analyzed by using the elastic wave equation of bimetal materials.In the process of numerical simulation,only change one of the physical parameters,i.e.P-wave velocity,S-wave velocity,material thickness and density.From the simulation results,it is found that the change of density has the least effect on the dispersion curve of Lamb wave.The other three physical parameters have a greater effect on the dispersion curve of Lamb wave.Secondly,the directivity characteristics of the line source laser excited ultrasound are studied by using the experimental system of detecting the double-layer non-metallic materials.At the same frequency,the directivity of(6₀ mode is better than that of₀ mode.Finally,the time-domain signals at different positions are obtained by using the step scan laser excited samples.Through the two-dimensional Fourier transform of the signal identified the dispersion curves of broadband Lamb wave propagating in different double-layer materials.Finally,the least square method is used to fit the simulation data with the experimental data,and the elastic parameters of the rubber material are obtained in the complex field.The fitting results in the real field is in good agreement with the values in the literature.Through the above preliminary study,the feasibility of laser-induced broadband Lamb wave in non-metallic double-layer materials is verified,which provides a feasible theoretical and experimental method for the characterization of double-layer damping materials.