Research On Self-excited And Self-retracting Anchor Bolting Detection System Based On Magnetostrictive Mechanism

Anchor bolt support plays an important role in tunnel,railway and highway,water conservancy and hydro power construction projects,but due to the complex application environment,and the general project is hidden,its quality problems are not easy to be found,the effect of anchor bolt support is affected,which may seriously cause major safety accidents.Therefore,it is of great significance to conduct timely and accurate quality detection and judge the bolting support.Specific research contents are as follows: Based on the detection mechanism of magnetostrictive longitudinal guided wave,this thesis uses the finite element numerical simulation method to design a self-excited and self-retracting longitudinal guided wave transducer suitable for the anchoring detection system of bolt,and studies the anchoring quality detection of bolt.Finally,the experimental platform is built by combining the simulation to verify the correctness of this research.The main work contents are as follows:(1)The research background and significance of this topic are discussed.According to the basic theory of guided wave,MATLAB software is used to solve the relevant equations and draw the dispersion curve,which provides a theoretical basis for the subsequent detection of bolt anchoring system.Based on the theory of magnetostrictive guided wave detection,combined with the principle of magnetostrictive transducer,the energy conversion equation between multiple physical fields is derived,and the physical equation designed in the process of energy conversion is derived.(2)The numerical simulation model of the transducer was constructed,and the influence law of the AC magnetic field and bias magnetic field parameters of the self-excited and self-retracting array transducer on the received signals was analyzed.The AC magnetic field parameters included the number of turns of the AC coil,the selection of the distance between the coil and the anchor rod,and the bias magnetic field parameters included the selection of the number,length and width of the magnetic block.Taking the number of turns of AC coil and the distance of AC coil as variables and the output voltage amplitude as the objective function,the coil parameters were optimized by the Beetle antennae search algorithm,and compared with the simulation model,to verify the feasibility of the Beetle antennae search algorithm applied in the optimization design.(3)COMSOL multi-physical field finite element simulation software was used to establish the detection model of bolt anchoring system by numerical simulation method.The free bolt and anchor solid models of array transducer structure and ordinary sleeve transducer structure were established respectively to detect the length and anchor length of free bolt,as well as the defects of free bolt and bolt anchoring.Compared with the common casing structure,the array transducer has higher detection accuracy,can better characterize the important characteristics of echo signal,and can be used to improve the amplitude of the received signal and improve the recognition ability of defects.(4)The experimental platform of anchor anchoring quality detection was built,the length of free bolt and the length of solid anchoring section of anchor were measured respectively,and the defect location of free bolt was detected.The characteristics of experimental received signals were consistent with those of simulation signals.In order to solve the problem that the received signal in the experiment contains a large amount of noise,a parameter optimization method of Variational Mode Decomposition(VMD)taking the sample entropy as the target function is proposed for noise reduction.Compared with the variational mode decomposition algorithm,this method has better noise reduction effect.