申伟 郑芳彤 李冬生

摘 要：为有效识别车辆荷载作用下钢桥面板的早期疲劳裂纹，进行钢板疲劳裂纹非线性Lamb波检测的数值模拟和试验研究。基于声接触非线性理论，提出了首波能量、拟声速和非线性参数3个损伤指标。试件同时考虑了孔洞缺陷、宏观裂纹和疲劳裂纹3种类型的缺陷，其中，疲劳扩展裂纹通过疲劳加载试验生成。在三维数值模型中，通过零长度非线性弹簧单元模拟闭合裂纹的“呼吸效应”，以模拟Lamb波与疲劳裂纹的局部非线性相互作用过程;进行了非线性Lamb波步进式扫描，并通过带通滤波器提取了二次谐波响应。研究结果表明：基波能量和拟声速指标对宏观缺陷敏感，而二次谐波能量和非线性参数对疲劳裂纹更敏感，综合3个损伤指标可以同时实现宏观缺陷和疲劳裂纹的识别和定位。

关键词：钢桥面板;疲劳裂纹;非线性Lamb波;非线性参数

中图分类号：U448.36 文献标志码：A 文章编号：2096-6717（2021）03-0135-07

Abstract： In order to effectively identify the early fatigue cracks of the steel bridge deck under vehicle loads， the numerical and experimental research on the nonlinear Lamb wave detection of steel plate fatigue cracks were carried out. Based on the non-linear theory of acoustic contact， three damage indexes were proposed， which are first wave energy， pseudo sound velocity and nonlinear parameter. Three types of defects including hole defect， macro crack and fatigue crack were considered in the specimens. Among them， the fatigue growth crack was generated by the fatigue loading test. In the three-dimensional numerical model， the "breathing effect" of closed crack is simulated by a zero-length nonlinear spring element to simulate the local nonlinear interaction process between Lamb waves and fatigue cracks. In the experiment， the nonlinear Lamb wave stepped scanning was performed， and the harmonic response was extracted through a band pass filter. The research results show that the first wave energy and pseudo sound velocity are sensitive to macro defects， while the harmonic waves energy and nonlinear parameter are sensitive to fatigue cracks. Combining the three damage indexes can simultaneously achieve the identification and location of macro defects and fatigue cracks.

Keywords： steel bridge deck; fatigue crack; nonlinear Lamb waves; nonlinear parameter

鋼桥面板在服役期间长期承受车辆荷载引起的交变应力作用，极易产生疲劳裂纹。金属的疲劳寿命一般分为3个阶段：即材料特性退化阶段、微裂纹的形成与积累阶段和疲劳断裂阶段[1]，一旦疲劳裂纹较大，进入失稳扩展阶段就可能造成构件的迅速失效，甚至造成结构整体坍塌。因此，对钢桥面板的早期疲劳裂纹损伤检测对于保障桥梁的结构安全尤为重要。

Lamb波技术因其传播距离远、检测范围广、对内部损伤敏感等特点已经被广泛用于板状结构研究和应用[2-3]。……