Application Of Variational Mode Decomposition In Bolt Anchorage Quality Inspection

Bolts are commonly used in various large-scale geotechnical projects such as railways,mines,tunnels,and slopes to improve the level of safety technology.However,in actual engineering,due to man-made damage and natural conditions,the bolt will have many defects such as rust and breakage,which will cause safety hazards.In the non-destructive testing of bolts,magnetostrictive guided wave technology has shown good application prospects in non-destructive testing and health monitoring of long-distance and large-scale structures due to its single-ended excitation,long propagation distance and non-contact properties.However,due to the low efficiency of electromagnetic ultrasonic transduction and high sensitivity to noise,the amplitude of the useful signal in the detection signal is relatively weak,and due to the harsh detection environment,the data drift of the sensor and the detection instrument itself.Interference,the data collected by the magnetostrictive guided wave technology is often submerged under strong noise,which brings great difficulties to the quality inspection of the bolt.This paper mainly studies the detection of bolt anchorage quality,starting from the signal processing of magnetostrictive guided waves.The main research contents are as follows:(1)Explain the basic principle of bolt anchoring,non-destructive testing method and data processing method of wave reflection method.The acquisition platform of magnetostrictive signal is introduced,and the principle of bolt magnetostrictive detection technology is explained in detail.The excitation and acquisition process of the guided wave is introduced,and the next extension is prepared.(2)In the variational mode decomposition,the parameter selection has a great influence on the decomposition effect,especially the interaction between the parameters directly affects the decomposition effect.Cuckoo search algorithm is a new heuristic intelligent algorithm.In this paper,cuckoo search algorithm(CS)is used to optimize the parameters of variational mode decomposition.Kurtosis is used as a measure to optimize the system parameters a and K of variational mode decomposition so as to achieve the best decomposition effect.The superiority of the variational mode decomposition after optimization of the cuckoo algorithm is verified by the simulation signal of the simulated vibration signal.(3)For the complex and noise interference characteristics of actual magnetostrictive guided wave vibration signals,this paper applies a method based on parameter optimization for variational mode decomposition(VMD)and independent component analysis(ICA)to the bolt.Magnetostrictive signals for better noise reduction.The cuckoo algorithm is used to search the optimal parameters of the VMD,and then the optimal parameters of the VMD decomposition are obtained.The signal can be optimally decomposed,and each component after decomposition is reconstructed according to the permutation entropy,and the signal is reconstructed.The original signal is subjected to FastICA demixing to realize the separation of the echo signal and the noise signal,and the wavelet signal is filtered to remove the glitch,and the noise-reduced signal is obtained.The analysis results of the actual collected data show that the proposed method has better noise reduction effect.