The Numerical Simulation And Debonding Detection Of Broadband Guided Wave Propagation Of The Anchors

In recent years, bolt anchorage technology are widely used in mining,highway, water conservancy and hydropower and other kinds of underground engineering and slope care in construction engineering. In the process of utilization, the anchor rod are defected due to the corrosion and fatigue destruction, leading to frequent engineering accident, which not only causes incalculable economic losses, but also brings serious influence on social environment. At the same time, anchor is a highly mechanical component, and most of the anchor rod anchors belong to concealed work, so its safety test is difficult in some degree. People has been adopting the drawing method to test the quality of anchor rod anchor all the time, and this method is very intuitive and reliability, which is one of the biggest advantages of this method, but the biggest drawback of this method is the destruction. The drawn anchor will produce larger deformation, resulting in the loss of inherent anchorage force in most anchor rods. So the "drawing" test is only suitable for small amount of spot check in real life. The bigger workload and inconvenient operation, not only take hours and not economic, but also is not suitable for field testing.In this article, the low-frequency ultrasonic guided wave was applied to debonding nondestructive testing of the anchoring bolt in service, the difficulty is that the bolt and the surrounding media will influence each other, so that making the guided wave propagation is more complex, as well as increasing the difficulty of the analysis of the guided wave signal. The broadband signal was used as the excitation signal in this article, firstly,it is based on the broadband signal propagation characteristic of the anchor rod in the embedded depth, and used the wavelet packet to decomposing the test signal, it is obviously that the different defects in the form of the broadband signal response characteristics of different frequency bands. But due to the defects and the response is not monotonic relationship between the signal characteristics, therefore, combining wavelet packet decomposition and neural network in this paper, establishing thecorresponding relation between test signal and damage characteristics, so as to realize the defect detection of the anchor.In this article, the main work could be stated from the following several aspects:(1) The adoption of low frequency broadband guided wave applied to anchor in service the debonding of the nondestructive testing methods;(2) Using ANSYS-LSDYNA to conduct numerical simulation analysis of the anchor rod, Used the wavelet packet to decompose broadband guided wave signal, established the wavelet packet basis function and wavelet packet decomposition layers, and the characteristics of the response signal based on wavelet packet was analyzed;(3)We considered the wavelet packet energy spectrum as the input vector,while the damage situation as the output vector. We constructed the BP neural network,to training a neural network applied to anchor nondestructive testing.The numerical results showed the BP neural network can effectively identify the flaws of the anchor debonding, and can be used to identify the defect position;(4) The tested polluted by noise were also used to identify the anchor integrity. The simulation showed an excellent identified results when noise level is less than 5%.