基于Lamb波群速度修正的复合材料结构损伤定位

摘要

As the barely invisible damages are often induced during the manufacturing processes or in-service applications,the material strength will degenerate and the performance of structure will decrease.Lamb wave based damage detection method can be used to identify the damages effectively.However,due to the complicated amplitude modulation,the distribution of energy spectrum will shift which brings challenge to group velocity determination.As the group velocity often determined by the center frequency of the excitation,the error will be induced when the distribution of energy spectrum is changed.In this paper,on the basis of amplitude modulation curves,its influence on energy spectrum shifting is investigated through simulation and experiment.Furthermore,the group velocity correction method is proposed to improve the damage localization accuracy.The experiment is carried out on a T300/3231 composite laminates.The imaging result shows higher accuracy when using corrected velocity,which verifies the efficiency of the proposed method.%复合材料结构在制造和服役过程中易产生不可见损伤,会降低结构强度,影响设备安全性能.基于超声Lamb波的结构健康检测方法可有效地实现对结构损伤的识别.然而,由于受到检测系统复杂的幅值调制作用,接收信号将发生频谱能量分布偏移.在定位检测过程中,群速度的选择以激励信号的中心频率为准,当激励信号的频谱受到较强幅值调制时,此时用于定位的群速度值将不再准确.在幅值调制特性的研究基础上,通过仿真和试验方法,探究了幅值调制对信号频谱能量分布的影响;进而提出了基于频谱偏移的群速度修正方法,并将此方法用于改进的延时叠加算法中以提高损伤定位精度.试验以T300/3231碳纤维复合材料板为对象,对比了群速度修正前后的损伤成像结果.结果显示,经过群速度修正后的定位精度优于未经过修正的结果,验证了群速度修正方法的有效性.