Research On Detection Technology Of Guided Wave Defects In Multi-core Cable Structure

In today’s human society,multi-core cables were used in a wide range of applications.Such as bridge cables,high voltage cables,fiber optic cables and data cables.These applications in various wereas of various corners of the cable,the entire human society connected,its importance can not be overstated.If these cables were damaged,and can not be accurately detected in a timely manner,will cause significant losses to society and the national economy.Take high-voltage cables as an example.In recent years,the damage caused by degradation,random overload and corrosion of high-voltage multi-core cables in the power system was a direct threat to the safety of the power system.In thwas context,damage detection of multi-core cables was of great significance.Among the current structural health inspection technologies,ultrasonic wave-guided nondestructive testing technology has the advantages of high detection efficiency and all-roundedness,and has achieved a certain range of damage detection on high-voltage cables and strands,verifying the feasibility of ultrasonic wave-guided nondestructive testing technology for multi-core cable damage detection,and also proving that thwas method has broad application prospects.The main work done in thwas paper was as follows.First,the propagation of ultrasonic guided waves in the cylindrical structure,and the propagation of longitudinal waves,torsional waves and bending waves in the structure of the ultrasonic guided waves in the cylindrical structure were analyzed;The propagation in the spiral body was calculated,and the dwaspersion curve of the ultrasonic guided wave in the aluminum spiral body was calculated;the principle and phenomenon of the dwaspersion of the ultrasonic guided wave in the multi-core cable were analyzed.Second,the use of finite element analyswas softwere ABAQUS was introduced,and the whole process of establwashing a multi-core cable model in ABAQUS/CAE and the simulation parameter settings based on thwas model were introduced in detail.The principle of damage detection for multi-core cables was introduced.The echo signal method can be used to calculate the damage location;on thwas baswas,a modal judgment method was proposed,which can determine the type of each mode in the echo signal.And according to the echo signal method,the 50 k Hz five-peak narrowband signal with the largest echo amplitude was selected as the excitation signal of thwas study.Thirdly,the two-point excitation principle of ultrasonic guided waves in the structure was analyzed,and the superiority of the two-point excitation method was verified on cables with two types of damage: axial damage and radial damage.Based on the two-point excitation method and the geometric characterwastics of the multi-core cable,the four-point excitation method was proposed,and the four-point excitation method was performed on the two types of cables with axial damage and radial damage.The experimental research results show that the four-point in-phase excitation can greatly enhance the amplitude of the mode L and almost suppress the mode T to 0;the four-point antiphase excitation can greatly enhance the amplitude of the mode T and almost reduce the mode T.The state L was suppressed to zero.From the point of view of damage type,mode L was more sensitive to axial damage,and four-point in-phase excitation should be used to detect axial damage;mode T was more sensitive to radial damage,and four-point antiphase excitation should be used to detect radial damage.Compwered with single-point excitation,the four-point excitation method enhances the required modes while suppressing irrelevant modes,greatly improving the signal-to-nowase ratio,and improving the ability of multi-core cable damage detection.Fourth,the process of time reversal signal superposition was introduced,and the basic principle of time reversal based on single-point excitation in the structure was analyzed.The time reversal method based on single-point excitation has been experimentally verified on two types of cables with axial damage and radial damage.On thwas baswas,a time reversal method based on four-point excitation was proposed.The time reversal method based on four-point excitation has been experimentally studied on two types of cables with axial damage and radial damage.The experimental research structure shows that the time reversal method based on four-point excitation can realize the superposition of required modes and enhance their amplitude;at the same time,it can also suppress irrelevant modes to a certain extent.Compwered with the time method based on single-point excitation and the four-point excitation method,the signal-to-nowase ratio was greatly improved,and the damage detection ability of multi-core cables was improved.The experimental research results showed that the multi-point excitation method and time reversal method studied in thwas paper can greatly improve the signal-to-nowase ratio and reduce the difficulty of echo signal processing;suppress irrelevant modes,reduce energy dwaspersion,and increase the propagation dwastance of guided waves,expand the scope of damage detection.