Study On Tomography Method Of Aluminum Plate Defects Based On Ultrasonic Guided Wave

Aluminum plate has excellent characteristics such as light weight and corrosion resistance,and is widely used in aerospace,automobile,shipbuilding and other industrial fields.However,in the process of manufacturing,processing,transportation and use of aluminum plates,pitting corrosion,cracks and other hard-to-see damages will inevitably occur.If information such as the location and extent of damage is not obtained and repaired in time,these damages will continue to expand over time,eventually causing equipment failure and catastrophic consequences.As an efficient and safe detection method,ultrasonic guided wave nondestructive testing technology provides a feasible solution for the damage detection of large-area aluminum plates.Based on Lamb wave,this paper conducts in-depth research on the imaging method of aluminum plate thinning defects.The main contents are as follows:The wave equation of guided ultrasonic waves in the sheet and the ultrasonic inverse scattering equation of defect reconstruction are deduced,and the vector integral equation is discretized by the method of moments,and the matrix inverse scattering equation is obtained.In order to verify the influence of the Euler prediction correction algorithm and the truncated complete least squares algorithm to solve the inverse scattering equation on the imaging effect.The finite element method is used to establish the simulation model of the guided wave detection of the aluminum plate,and the data including the direct wave and the reflected wave are collected by the annular transducer array.Simulation study found.If the truncated complete least squares method is used to solve the problem,when the regularization parameter is small,the reconstructed image can better represent the internal information and position information of the defect(In the imaging results of the two aluminum plates tested,the defect deviations were 2.50 mm and 0.76 mm,respectively).If the Euler prediction correction algorithm is used to solve the problem,the reconstructed image can better represent the defect edge information and position information(in the imaging results of the two tested aluminum plate models,the defect deviations are 1.12 mm and 0.88 mm,respectively).Because the reflected wave and the direct wave interfere with each other,the images reconstructed by the above two methods have the problem of blurred edges.In order to overcome this problem,this paper proposes a method of weighted fusion of the imaging data obtained by the two solving methods.One of the aluminum plate models is simulated and verified,and the imaging results show that the reconstruction accuracy of defect edges and positions has been significantly improved(the imaging error of defect positions is 0.31 mm).In order to verify the feasibility of the above defect imaging method in application,an experimental platform for guided wave detection was built,and a ring transducer array was used to collect the experimental data.Considering that the imaging algorithm has high requirements on the accuracy of the experimental data,the variational modal decomposition method is introduced to denoise the experimental data.The imaging detection experiment was carried out on the right defect on the aluminum plate,and it was found that the experimental results and the simulation results had a high degree of matching.It is shown that the Euler prediction correction algorithm solves the inverse scattering equation constructed by the method of moments,which can realize the quantitative detection of the position and depth of the thinning defect of the aluminum plate,and the quantification error of the depth is within 0.2mm.