Study On Defect Detection Of Aluminum Plate Based On Ultrasonic Lamb Wave

Plate structure is widely used in large oil storage tanks,aerospace,automobile manufacturing and other fields,however,this kind of structure has the characteristics of large detection area and difficult on-line detection.Ultrasonic Lamb wave can be used to detect the defects in the plate structure.Based on this,the paper studies the hole defects in the plate structure.The specific work of this paper is as follows:(1)The dispersion characteristics and multimodal characteristics of the ultrasonic Lamb wave are studied,and the symmetrical SO mode is determined as the final detection mode.The frequency characteristics of the ultrasonic Lamb wave in the plate are studied,and the position of the sensor and the optimal excitation frequency are determined.(2)This paper presents a new method of data processing,which can greatly improve the accuracy of defect location,which is based on the error caused by the original experimental data.Firstly,a distance coefficient is defined according to the position between the excitation sensors and the defect.Then,the relationship between the experimental data of different distance coefficients and the imaging accuracy is studied by using the square array as an example.The experimental results show that the distance coefficient is smaller of the experimental data for imaging the more accurate positioning of the defect.Finally,this paper analyzes the reason of this phenomenon from two angles:time domain signal and simulated signal scattering field.(3)Based on the influencing factors of defect detection accuracy,the influence of array type,location of defect and defect type on defect detection positioning is systematically studied.The research results of this paper have some engineering application value,which has applied ultrasonic Lamb wave to the structural health monitoring of plate structure.