Damage Identification Of Pressure Structures Based On Lamb Wave

With the development of ocean exploration,the application of underwater vehicle have been paid more and more attention.Because of the particularity of the underwater working environment,it is difficult to monitor it in real-time by traditional monitoring methods,and the importance of the pressure-resistant structure as the main supporting part of the underwater robot is self-evident.After comparing and analyzing the common monitoring methods,the damage identification of pressure structures based on Lamb wave is studied in this paper.To detect the whole structure,a damage identification system of pressure structure based on Lamb wave is built,which can locate and image the damage.The main research contents and results of this paper are as follows:(1)Based on the theory of elasticity,the motion equations of Lamb waves in plate and spherical shell structures are derived,and the corresponding dispersion curves of group velocity and phase velocity are drawn,and the propagation law of Lamb Wave in structure is analyzed.Building a pressure structure health monitoring system based on Lamb wave,which is divided into three parts: excitation of Lamb Wave,signal acquisition and signal post-processing,the program is programmed to collect the data.The effectiveness of the platform is verified by experiments.(2)The optimal excitation center frequency is determined by experiment.And the collected signal is filtered and denoised.To analyze the aluminum plate with defect,to obtain the echo signal and to read the arrival time of the Echo Peak caused by the damage through the research of the damage identification method of the Lamb wave based on the ellipse location.Damage imaging is achieved by comparing the difference of the signals before and after the damage and the distance from the excitation to the receiving sensor,the multi-sensor data are fused and the damage is imaged by the probabilistic damage detection and reconstruction algorithm.(3)Based on the analysis of the propagation law of Lamb wave in the spherical shell,the method of damage location in the spherical shell structure is proposed by the transformation of the cartesian coordinate system and the spherical coordinate system,and the sensor layout of the spherical shell specimen is established,and the effect of damage parameters on Lamb wave amplitude is analyzed.The imaging of the damage of the spherical shell structure has certain reference value for the practical engineering application.