模态声发射在结构材料缺陷定位中的研究

针对在役结构材料中间时存在静态和动态缺陷时难于进行缺陷平面定位的问题，利用声发射技术实时记录声发射波形时域信号的特点，结合薄板中Lamb波的频散特性和Gabor小波时频分析方法，研究并提出了一种新的实用定位方法。该方法通过先后采用三角形和椭圆平面定位方法可分别反演动态缺陷、静态缺陷的位置，并利用低频时频散不明显的对称模态波速和同一时域信号的相对时差来避免波速变化与各传感器间灵敏度差异和门槛值不同对椭圆定位精度的影响。经过实验研究证明，应用这种方法反演得到的缺陷位置和实际缺陷位置一致。

EXPERIMENTAL STUDY ON MODAL ACOUSTIC EMISSION FOR DEFECT LOCATING IN STRUCTURAL MATERIALS

It is difficult to locate defects in planar structural materials in service when both static defect and dynamic damage exist in the same structure.A new and applicable approach of planar locating is presented based on using characteristics of acoustic emission technique and recording real-time wave shape in time domain,combining dispersive characteristics of lamb wave and arrival time of different modes determined by using peak magnitude of Gabor wavelet time-frequency analysis.This approach can locate static defect and dynamic damage in sequence by using triangular locating and elliptical locating.Furthermore,utilizing wave speed without dispersive characteristics at certain frequency of symmetrical modal shape and relativ time difference of the same signal at some frequency in time domain can reduce error of elliptical locating which is easily affected by wave speed change and different sensitivities among various sensors.That the locating result using the above method is close to the position of the real damage is demonstrated by experiments.