基于波包能量的裂纹扩展监测实验研究

Experimental study on crack growth monitoring based on wave packet energy

采用主动Lamb波监测技术对铝板结构中的疲劳裂纹扩展进行了实验研究.首先通过布置在结构中的压电片激发并采集Lamb波信号.然后分别把Lamb波信号的原始信号、信号包络及其特定尺度上的小波系数模值定义为波包,并建立了不同定义下波包能量的计算公式.将结构在裂纹扩展过程中传感器所接收的Lamb波S0模式波包能量与健康状态下所得到的波包能量进行对比,得到每个裂纹扩展阶段的能量差,将其归一化后得到相应的裂纹损伤特征参数.最后通过实验分析得到该损伤特征参数与裂纹扩展程度之间的对应关系,从而揭示出Lamb波随裂纹扩展的变化规律.实验结果表明,利用上述方法所得到的裂纹损伤特征参数随裂纹扩展表现出特定的变化规律.该规律对于裂纹监测的进一步研究具有促进作用.

Active Lamb wave diagnostic technology is adopted to monitor fatigue crack growth in the experimental study. First, a Lamb wave signal is generated and collected by piezoelectric （PZT） wafers embedded in an aluminium plate. With wave packet defined as original signal, signal envelope and modules of wavelet coefficients at a specific scale respectively, the calculation formula of its energy is then established. The normalized difference between the wave packet energy of So mode of the Lamb wave received when a crack grows and the energy in the initial state is determined as a crack damage index. Finally, experiments are designed to research the relationships between the damage index and the real crack growth. Experimental results show that the damage index increases with the crack growth in a certain rule. This rule can promote the crack monitoring research.