Study On The Ultrasonic Guided Wave Spreading In The Numerical Simulation Of Bolt Anchoring System

In recent years, Bolt anchoring technique has been widely used in engineering at home and abroad. The effective methods to detect anchor in the project are required urgently. Traditional drawing method and core method are destructive which limits its use in the project. In order to overcome these shortcomings, researchers use a variety of ways to test and find out that the Nondestructive Testing Method gets the best results. Ultrasonic guided wave method is a new approach in the field of nondestructive testing. Because the detection distance of body wave is very short and which help researchers to remove their concentration to the guided wave, and now it was widely recognized that the guided wave dispersion characteristics are very sensitive and could analyze the quality of the project precisely. The characteristics of Guided-wave are multi-modal and dispersion. Slightly change may cause the different results due to its complexity. In addition, the experiments are blindness, time-consuming and also heavy workload. Numerical simulation could overcome these shortcomings very well, and it is an indispensable tool to study the guided-wave. Based on Guided-wave theory and Numerical Simulation Methods, we try to explore a method to simulate the way that guided wave spreads in the anchor; to master the core technology to simulate the guided waves; and to do a lot of exploration on the reliability, accuracy of simulation. Meanwhile, the command stream is optimized to make it simple, efficient and eliminating the need for manual debugging link.Based on the correct simulation model, a lot of simulation work were did on unanchored and anchored bolts respectively, and to explore the unanchored bolt structure as three following aspects:One is the dispersion curve characteristics of unanchored bolt which has been very clear in theory which appears that the simulation results corresponding is very accurate. The second is to do different simulations on different frequency guided-wave, finding that for particular anchor structure, there exists an optimal excitation wave. The third is to simulate the same frequency but different structures bolt. Three aspects were studied for the anchored bolt:First, the dispersion characteristics of the anchored bolt, which is not very clear in theory. Appropriate explorations were done by simulating in the paper. Followed is the effect experiment resulted by the thickness of concrete anchored bolt model, the purpose is to explore a reasonable size model for research. Finally, to simulate the different quality of anchored bolt. Important conclusions are as follows:First, three-dimensional solid model are more realistic, but the guided wave simulation high requirements are too computationally. Ax symmetric model could solve this problem very well. In many cases, longitudinal modes actually only used, under this situation, the ax symmetric model is the best option.Second, the body-wave theory indicates that in numerical simulation of one wavelength within8units could control the deviation in less than1%. Through the hundreds and thousands of simulations on guided waves, results indicate that it is far from the requirements to do the simulation within one wavelength of8units. In one wavelength within about30units could give a more accurate simulation results, and this also can be used as the reference.Third, the number of load curve cycle are usually ignored, which could lead sever effects on the experiment results. It is available to increase the number of cycles at the high frequency condition.Fourth, the guided wave velocity changes greatly with the different radius in unanchored bolt model. It is relatively easy way to explore the optimal excitation wave under a specific condition by the theory of solve the dispersion curve and the numerical simulation methods.Fifth, the wave spread speed is a function of wave frequency multiplied by the radius of the waveguide (f*a). In unanchored bolt model, the waveguide radius is the radius of a bolt (a), but it is not clear in the bolt anchoring system theory. People might think is also "a". This paper studies get the conclusion that in the bolt anchoring structures the concrete and anchor radius form the waveguide body together. They work as a whole but the radius plays a decisive role to the dispersion curves when anchor concrete thickness is not too thick. When anchoring thickness is very large, the impacts resulted by concrete is lower since the guided wave is spread in the center of the reinforced. Further study of dissemination law is needed.