移动连续激光源激发Lamb波的材料弹性性质反演  

Elastic Property Inversion of Materials via Lamb Waves Generated by aMoving Continuous⁃Wave Laser

作　　者：李秋雨 李政 陆健[1] 阚威威 沈中华[1] Li Qiuyu;Li Zheng;Lu Jian;Kan Weiwei;Shen Zhonghua(School of Science,Nanjing University of Science and Technology,Nanjing 210094,Jiangsu,China;COMAC Shanghai Aircraft Manufacturing Co.,Ltd.,Shanghai 201324,China)

机构地区：[1]南京理工大学理学院,江苏南京210094 [2]中国商飞上海飞机制造有限公司,上海201324

出　　处：《中国激光》2024年第8期111-118,共8页Chinese Journal of Lasers

基　　金：国家自然科学基金(11974186,61975080);江苏省自然科学基金(BK20200070);中央高校基本科研业务费专项资金(020414380195)。

摘　　要：通过测量板状材料中Lamb波的频散曲线可以反演出材料的特性参数,因而这种方法在材料表征、评价和无损检测等领域具有广阔的应用前景。基于移动激光源法测量了薄板中Lamb波的频散曲线,通过高速转镜使聚焦的激光线源在样品表面以与相应Lamb波模式匹配的速度移动,当激光移动速度与Lamb波相速度一致时,可以以较高的效率激发出此Lamb波模式。通过改变转镜的转速,即改变激光线源的移动速度,记录不同移动速度下所激发的Lamb波频谱,可以得到Lamb波的频散曲线。在此基础上,结合粒子群优化算法反演了铝板以及聚苯乙烯板中的纵波波速与横波波速。在仿真中,开展了不同模式和频厚积处频散特性对材料参数的敏感度分析,并比较了不同噪声水平下以及不同模态频散数据选取所对应的拟合效果,讨论了2500~4000 m/s相速度区间基于频散曲线的反演敏感度问题。最终基于移动激光源实验中所提取的铝板中Lamb波的频散数据进行参数反演,结果显示,纵波声速和横波声速的反演误差均小于1.5%,证明了该方案的有效性。Objective Accurate mechanical properties of materials,including Young’s modulus,Poisson’s ratio,and longitudinal and shear wave speeds,are essential for material evaluation and testing.A major challenge arises when dealing with multimodal ultrasound Lamb waves,especially those that closely approach or intersect in the spectrum or dispersion curves.This complexity is often due to hardware limitations,such as the bandwidth of generation and detection.Furthermore,accurately distinguishing these modes in dispersion curves,by identifying spectral peaks through the wavenumber resolution offered by the two-dimensional Fourier transform method,often presents difficulties.Traditionally,most studies have relied on contact wedge transducer.However,laser ultrasound introduces a nondestructive testing method that significantly simplifies spatiotemporal modulation and enables non-contact generation detection.This approach is particularly advantageous for applications that require rapid material scanning,as it overcomes the challenges associated with traditional methods,enhancing accuracy and efficiency in material property analysis.Methods To address challenges in material parameter inversion,a novel approach was employed,utilizing a moving continuouswave laser source to generate multimodal Lamb waves in thin plates.This method was first validated through a material-parameter inversion study.Experimental findings,illustrated in Figs.4 and 5,confirmed the effective generation of specific Lamb waves with distinct phase velocities.Importantly,this non-contact phase-velocity matching method overcame the limitations typically encountered with transducer use in contact scanning,enhancing the accuracy of dispersion curve measurements within the targeted range.Further investigations focused on parameter sensitivities in the fitting process,specifically for aluminum plates within a phase velocity range of 2500‒4000 m/s and a frequency-thickness product range of 1‒20 MHz·mm.Additionally,as shown in Figs.2 and 3,simulations and

关 键 词：测量 激光超声 参数反演 移动连续激光源 粒子群优化算法 

分 类 号：TG113.25[金属学及工艺—物理冶金]