孙晓强 张晋源 胡宁

摘要 为方便利用非线性Lamb波脉冲激励零频分量进行板材结构早期损伤超声无损健康监测，基于二次材料弱非线性，在基波和零频分量群速度相等的情况下，推导非线性Lamb波脉冲激励零频分量的理论解。以汉宁窗调制的短脉冲激励为例，建立仿真模型，提取仿真零频信号，制作零频信号传播动画，展示对称模态零频分量克服相速匹配条件的限制进而可持续累积的特征。理论仿真结果与分析讨论表明，零频模态为对称模态，零频形貌与窗函数形貌相似，基波群速度失配和色散可以分散零频分量能量进而影响零频形貌，零频分量可持续累积特性不受其影响，与二次谐波和混合波检测技术相比，非线性Lamb波零频分量检测技术具有一定的优势。

关 键 词 结构健康监测;非线性Lamb波;零频分量;材料弱非线性;材料早期损伤

中图分类号 TG115.285;TB553     文献标志码 A

文章编号：1007-2373（2021）06-0001-12

Abstract For the convenience of using nonlinear Lamb wave pulse excitation zero frequency component to monitor plate-like material early stage damage， based on the quadratic weak material nonlinearity， the theoretical solution of zero frequency component induced by nonlinear Lamb wave pulse is derived under the condition that the group velocities of fundamental wave and zero-frequency component are equal. A simulation model is established. A Hanning windowed tone burst signal is adopted as the excitation signal. The propagation animation of zero frequency component is obtained. The limitation of phase-velocity matching is overcome and the energy carried by zero frequency component can accumulated continuously. Theoretical results simulation results and discussion analysis show that the shape of the symmetric mode zero frequency component is similar to the shape of the window function. The shape of zero frequency component is influenced by zero frequency component energy dispersion which induced by the group velocity mismatch and dispersion of the fundamental wave. The sustainable accumulation characteristics of the zero frequency component are not affected. Compared with the second harmonic and mixing wave detection technology， nonlinear Lamb wave zero-frequency component inspection technique has certain advantages.

Key words structural health monitoring; nonlinear Lamb wave; zero frequency component; weak material nonlinearity; material early stage damage

0 引言

板壳结构性能优异，被各行各业广泛采用。这些板壳类结构材料在使用过程中，或多或少会受到应力、高温、高压和腐蚀等的作用，非常容易产生疲劳、塑性、腐蚀和蠕变等损伤，使得板材性能逐渐退化，容易引起爆炸、断裂和危险物质泄露等安全事故，造成重大社会和经济损失。因此，研究强有力的无损监测技术，对这些板壳结构定期进行可靠性检测评价和维护，是我国国民经济生产及生活中一个非常重大的研究课题。

经过多年的研究和发展，目前已经存在多种，相对较为成熟的无损检测和评价技术。……