Research On Damage Detection And Localization In Plates Based On Ultrasonic Lamb Wave

The plate structure is widely used in shipbuilding,aviation industry,etc.Plates are prone to fatigue,corrosion or other types of damage,which is a huge security threat,due to continuous external loading during the long time service.Therefore,structural health monitoring of the flat panel is of particular importance.Lamb wave has advantages of little attenuation,small wavelength and sensitivity to small damage,which makes it suitable for large-area nondestructive testing of plate structures.The key to ultrasonic Lamb wave detection is to study the interaction between damage and Lamb wave and damage localization algorithms.This research mainly focuses on Lamb wave motion theory and damage localization algorithms,and theoretical analysis,numerical simulation and experimental approach are used in the study.Firstly,the fluctuation characteristics of the Lamb wave basic mode S0 and A0 and its interaction with damage in plate was researched by combing the theoretical derivation and numerical simulation.The dispersion curves of an aluminum plate were derived by MATLAB.Finite element analysis software ANSYS was used to simulate Lamb wave propagation and its interaction with a through hole in an aluminum plate.Secondly,a LabVIEW-based ultrasonic Lamb wave data acquisition platform was built.The following research mainly focuses on damage localization algorithms.A new method entitled distance subtraction method used to measure Lamb wave group velocity was proposed,which helps eliminate dispersive effect.Practical engineering problems are considered in the application of RAPID algorithm.An improved RAPID algorithm was proposed to improve damage imaging resolution,and it was implemented in aluminum plate's non-damage,single damage and multiple damage localization study.In addition,the situation of failure of part of sensors are considered in real inspection environment,then the damage localization ability of the remaining sensors networks was studied.Finally,neural network was used to localize damage in the aluminum plate,and it successfully predicted new damage locations.Several damage detection and localization algorithms are discussed in this paper,which provides technical support for the application of the technology in practical engineering.