弱界面分层结构中的非线性兰姆波

对弱界面分层结构中兰姆波的非线性效应进行了研究。在二阶微扰近似条件下,将兰姆波传播过程中的非线性效应处理成兰姆波线性波动响应的一个二阶微扰。采用界面弹簧模型对分层结构的弱界面性质进行描述。根据模式展开分析方法,伴随基频兰姆波传播所发生的二次谐波可视为由一系列二倍频兰姆波模式叠加而成。弱界面性质的变化将从多个方面对二倍频兰姆波模式的展开系数产生影响,尤其是弱界面性质变化导致的兰姆波相速度的改变可显著地影响到二倍频兰姆波模式随传播距离的积累增长程度。分析结果表明,兰姆波的非线性效应可有效地表征分层结构的弱界面特性。

Nonlinear Lamb wave propagation in layered planar structures with weak interfaces

Nonlinear effect of Lamb wave propagation in layered planar structures with weak interfaces has been studied in this paper. Under second-order perturbation approximation, the nonlinear effect of Lamb wave propagation may be treated as a second-order perturbation of linear response of Lamb wave propagation. The weak interfaces can be described by the interfacial spring model. According to the modal expansion approach for waveguide excitation, the second-harmonic fields of a fundamental Lamb wave propagation can be decomposed into a series of double frequency Lamb waves. It is found that changes in the properties of the weak interfaces will influence the expansion coefficients of double frequency Lamb waves in several aspects. Especially, changes in the phase velocities of Lamb waves caused by changes in the properties of the weak interfaces will remarkably affect the degree of cumulative growth effect of double frequency Lamb waves. The results obtained show that nonlinear effect of Lamb wave propagation can effectively be used to characterize the properties of weak interfaces in layered structures.