铝板中Lamb波检测的实验研究

Experiment investigations of Lamb waves in an aluminum plate

Lamb波在传播过程中具有频散及多模态特性,若相关参数选择不当,会导致在实际应用中信号相互叠加而无法识别。本文基于Lamb波的频散曲线是其频散方程实数解分布的特点,采用二分法绘制了铝板中Lamb波的频散曲线、波结构曲线和入射角曲线。根据曲线选择S0模态的Lamb波对1mm厚铝板中不同类型的缺陷进行检测。实验结果表明,S0模态的Lamb波对裂纹型缺陷和贯穿型缺陷十分敏感,但对于裂纹型缺陷,其幅值变化并不与缺陷大小成线性关系,并且S0模态Lamb波的声场指向性十分集中,在偏离声束轴线时无法检测到缺陷。

Lamb waves have dispersive and multi-modal characteristics during its propagation.In actual applications,the multi-modal signals overlap and the useful modes can not be identified if relevant parameters are not properly selected.The dispersion,wave structure and incident angle curves of Lamb waves in an aluminum plate are drawn with dichotomy based on the characteristics that the Lamb wave dispersion curve is the distribution of real solutions of a Lamb wave dispersion equation.S0 mode Lamb wave is selected to detect the flaws with different types in 1mm thick aluminum plate based on the dispersion curve.The results show that S0 mode Lamb wave is very sensitive to cracks and through defects; however,the amplitude of S0 mode don＇t change linearly with the defect size.Meanwhile,the sound field directivity of S0 mode Lamb wave is very concentrated,and the defects deviated from the beam axis can not be detected.