Damage Identification Research For Steel Plate Based On Lamb Wave

Steel plate is an essential component in the steel structure buildings; the damage in thesteel plate is unsafely for the integrity structure, so how to detect the damage accurately,effectively, to avoid the unnecessary personal injury and economic loss is our research subject.This paper invesgates relationship of the steel plate’s depth, size and location with the Lambwaves propagation to verify the detection’s feasibility and accuracy of the experiments.According to the knowledge of elastic dynamics, the paper derived the dispersionequation of ultrasonic Lamb wave. the paper got the dispersion equation’s numerical solutionby using Matlab program based on dichotomy, and discussed the ultrasonic Lamb wave’spropagation properties based on the dispersion curves. Calculated the different mode andfrequency of Lamb wave’s displacement distribution and discussed the detection’s sensitivityof different frequency to different damage forms through the displacement distribution. Thepaper researched the influence for the Lamb wave’s propagation properties through thechanges of material parameters (thickness and modulus of elasticity). With the decrease of thethickness of plate, the phase velocity and group velocity increases gradually, and the lowfrequency region is more sensitive to this change. High order modes of Lamb wave are moresensitive for the change of elastic modulus; however, the displacement in the plate isn’tshowing certain regularity to this change. The research on the wave structure and theparameters’ influence for the Lamb wave’s propagation properties is the foundation ofchoosing a suitable detection frequency and mode under different experimental conditions.The paper established the detecting experimental platform of Lamb wave. Theexperiment determined the propagation mode in the steel plate. The experiment got theconclusion that low frequency of A0,S0mode is more sensitive than high frequency to detectthe minor damage, it is also verifies the theoretical results. The paper finded out the A0, S0mode propagation energy’s influence by different damage diameters, and got the relation forLamb wave’s propagation energy and the distance between PZT and the damage’s location,and find the damage’s approximate location. Using the continuous wavelet transform andHilbert transform process and analysis the signals. Calculating the damage signal’s time delay,do the positioning research by using the ellipse localization technique. The experiments showthat this signals processing method combined the ellipse localization method can better identify the damage’s location on steel plate.