复合材料结构健康主动监测中激励信号的优化

利用L am b波频散方程及其数值求解得到的频散曲线,对L am b波模式及激励信号中心频率范围进行预测。建立了试验测试系统,利用集成在复合材料层合板上的PZT压电陶瓷片作为驱动器和传感器,激励并接收结构中激发的L am b波信号。对具有不同函数形式、中心频率和波峰数的信号激励,结构中传播的L am b波模式进行试验研究,为激励信号的选择与优化提供依据。利用H ilbert-Huang变换及H ilbert谱提取传感器信号特征,提出了L am b波信号在结构中传播时的能量衰减率和损伤敏感度两个考察指标,并据此对激励信号进行优化。实验结果表明,优化后的激励信号在结构中能激发出单一模式的L am b波(S0模式),有效地抑制了多模式现象的出现。同时,激发出的L am b波具有最低的能量衰减和最高的损伤灵敏度,响应信号特征明显,便于损伤识别。

Lamb Wave Excitation Signal for Structural Health Monitoring on Composite Structures

An optimal excitation signal is proposed to improve the effect of damage detection.Dispersion equations and dispersion curves of Lamb wave propagating in a laminated composite plate are utilized to predict the modes of Lamb wave and the domain of the center frequency of the input excitation signal.An experimental test system is set up.Lamb wave can be generated and received by two piezoelectric ceramic patches(PZT) mounted on the same surface of composite laminate as an actuator and a sensor.The Lamb wave propagating modes are experimentally analyzed under the different excitation signal parameters that include the function forms,center frequencies and wave peak number.The characteristics of sensor signals are extracted using Hilbert-Huang transform and Hilbert spectrum.Based on the Hilbert spectrum,two criteria for the energy attenuation ratio and the damage sensitivity of Lamb wave propagating in the structure are defined and used to optimize the excitation signal experimentally.Research results show that the single mode Lamb wave(S_0) can only be generated in the structure with the optimal excitation signal to realize the suppression on the multiple Lamb wave modes.The Lamb wave generated by the optimal signal has the lowest energy attenuation ratio and the highest damage sensitivity,so it is more suitable for damage detection.