宽频非线性超声法在混凝土扩展微裂纹的应用

Detection of Concrete Propagating Microcracks Based on Broadband Excitation Nonlinear Ultrasonic Modulation Method

混凝土微裂纹的扩展对于重要混凝土结构或者疲劳荷载下的建筑或桥梁的安全性和耐久性具有较大影响,传统的无损检测方法对微裂纹不敏感,针对此问题,提出一种利用宽频非线性超声调制原理检测混凝土扩展微裂纹的方法。借助扩展有限元仿真法,模拟超声激励含微裂纹混凝土模型产生应力波,对混凝土模型接收点的位移信号进行频谱分析,建立了微裂纹扩展长度与非线性调制法中所定义的损伤指标峰值之间的关系。通过仿真模拟和试验检测,研究了宽频激励下非线性超声检测荷载下扩展微裂纹的可测性,从而实现对混凝土微裂纹扩展趋势的实时动态监测。

The propagation of concrete microcracks has a great influence on the safety and durability of important concrete structures or buildings or Bridges under fatigue load.Traditional nondestructive testing methods are not sensitive to microcracks.In this paper,a method based on broadband excitation nonlinear ultrasonic modulation technology is proposed for detection of concrete propagating microcracks.By means of the extended finite element simulation method,the stress wave generated by ultrasonic excitation is simulated in the concrete model with microcracks.The displacement signal of the concrete model is analyzed by spectral analysis,and the relationship between the length of microcracks propagation and the damage index peak value defined in the nonlinear modulation method is established.Through simulation and experimental detection,the feasibility is studied for broadband excitation nonlinear ultrasonic detection of propagating microcracks under loading.Results show that the real-time dynamic monitoring can be realized for the propagation of concrete microcracks.