层状固体结构表面性质的非线性兰姆波定征方法

 提出用非线性兰姆波方法定征层状固体结构的表面性质,分析了层状固体结构表面性质变化对兰姆波二次谐波发生效应产生的影响。基于Ritec-SNAP系统建立了非线性兰姆波实验系统,当表面的覆层面积和覆层厚度发生变化时,在兰姆波具有强烈非线性效应的条件下,测量了兰姆波的基波及二次谐波的幅频曲线,结果显示表面性质的微小变化将显著地影响到兰姆波的二次谐波发生效率。借鉴声-超声技术中的应力波因子方法,定义了兰姆波应力波因子,实验结果表明,利用兰姆波二次谐波的应力波因子可对层状固体结构表面性质的变化情况进行准确定征。

Characterization of Surface Properties of Layered Structures Using Nonlinear Lamb Wave Approach

The nonlinear Lamb wave approach is presented for characterizing the surface properties of layered structures.The influences of changes in surface properties of layered structures on the effect of second-harmonic generation by Lamb wave propagation are analyzed.Based on the Ritec-SNAP system,the nonlinear Lamb wave experimental system is established.When the areas and thicknesses of coating on the surface of a given layered structure change,the amplitude-frequency curves both of the fundamental waves and the second harmonics of Lamb waves are measured under the condition that Lamb waves have a strong nonlinearity.It is found that the micro-changes in surface properties will obviously affect the efficiency of second-harmonic generation by Lamb wave propagation.The stress wave factor(SWF) in acousto-ultrasonic technique is used for reference.The SWFs of Lamb waves are defined.The experimental results show that the SWFs of second harmonics of Lamb wave propagation can well and truly characterize the changes in surface properties of layered structures.