超声导波在圆管结构损伤定位中的应用
Research on Ultrasonic Guided Wave-Based Damage Localization for Pipeline Structure

针对结构损伤会影响超声导波传播，提出基于超声导波损检测的结构健康监测方法。以内径为174 mm、外径为194 mm、材料为20#碳钢的圆管结构为例，根据频散方程利用数值法求解其纵向模态以及周向Lamb波频散曲线。同时考虑其频散曲线和波的结构，确定激励频率中心频率为80 kHz。在此基础上进行有限元仿真，验证圆管中导波的传播机理及特征。针对此频率圆管纵向模态导波以及周向Lamb波的频散特性、波的结构比较接近，且都与板中的Lamb波相似，从而提出了单点激励、多点接收，并采用椭圆定位的方法，实现圆管结构损伤定位。通过仿真和实验验证该方法对切槽、圆孔等损伤的识别效果，并对损伤定位误差的影响因素进行了分析。
Structure damage will affect the propagation of ultrasonic guided waves.Hence, non-destructive testing technology based on ultrasonic guided waves can realize structural health monitoring (SHM). A pipe with 174mm inner-diameter and 194mm outer-diameter, made of 20# carbon steel is used to investigate the damage localization in this study. Based on dispersion equations, numerical method is applied to obtain longitudinal and circumferential guided waves in the pipe structure. Central frequency of the incident signal is selected 80 kHz by simultaneously considering the dispersion curves and wave structure. Finite element method (FEM) is used to verify characteristics of guided wave propagation. According to the FEM analyses, characteristics and wave structures of longitudinal modes are close to those of circumferential waves, moreover, both of them are similar to those of Lamb waves in plate structure. Elliptical damage localization method is therefore proposed with one excitation and multiple captures for damage localization in the structure. Notch and hole are introduced to the pipe to verify effectiveness of the proposed method, and then analyzed influencing factors of damage localization deviation.