钢桥面板疲劳裂纹损伤非线性Lamb波检测的数值模拟与试验研究

Numerical and experimental study on fatigue crack detection of steel fridge deck using nonlinear Lamb waves

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。

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.