基于Lamb波传播路径分析的复合材料板中缺陷成像*

板型波导结构中的缺陷对Lamb波的传播会产生干扰，接收信号受干扰程度与缺陷和激励、接收传感器路径间的相对距离有关。提出一种基于Lamb波传播路径分析的多频率数据融合缺陷检测方法，对复合材料板中缺陷区域进行成像。采用压电传感器进行Chirp信号激励，由Chirp激励响应计算出具有不同中心频率的Tone burst信号，为成像算法提供多频率缺陷信息。对各信号中首次抵达波的包络峰值进行分析，确定缺陷所在位置同激励接收路径间的关系。选择同缺陷所在路径具有相近Lamb波传播速度的路径作为关注路径，结合椭圆成像算法和该路径中的缺陷散射信号信息计算出缺陷所在的椭圆轨迹。引入椭圆轨迹计算误差容限，对计算得到的不同频率下的椭圆轨迹进行筛选，将筛选后的椭圆轨迹进行融合实现缺陷区域成像。通过对复合材料板中缺陷区域的试验检测，验证了所提算法的可行性。

Defect Imaging in Composite Plates Based on Propagation Paths Analysis of Lamb Waves

The propagation characteristics of Lamb waves can be changed when they encounter a defect in plate style waveguides,which has close relationship with the relative distance between defects position and the propagation paths of Lamb waves among the transducer.A defect zone imaging method based on propagation paths analysis is presented to realize defect zone image in composite plates.To obtain enough defects information,a chirp excitation is stimulated by piezoelectric transducers,then abstract tone burst responses those have several of center frequency form the chirp responses.Through comparing the peak values of the signal envelops,the relationships between the defect and propagation paths are acquired.The paths have similar propagation velocities with paths those a defect located are chosen as interested path,then calculating elliptical tracks with the defect scattering signals with the elliptical imaging algorithm.The error tolerance is introduced to select the elliptical tracks calculated with difference frequencies.Detect zone image is realized by fusing the selected elliptical tracks.The feasibility of the proposed method is validated with experiments in a composite material plate.