Defect Detection And Evaluation Of Cable Structures

With the rapid development of large-scale infrastructure construction,the number of multi-core cable structures surges,these multi-core cable structures are used in all aspects of production and life,their health status and engineering life is very important,once the damage occurs and is not accurately identified and detected,the loss is not counting,which is of great significance to the damage research and application of such structures.In this paper,the application of electromechanical impedance technology and guided wave detection technology in the structural health monitoring of multi-core cable is studied.Taking aluminum multi-core cable as the research object,the coupling mechanism is designed to eliminate the technical application barriers.Combining the high sensitivity of electromechanical impedance technology with the wide detection range of ultrasonic guided wave technology,a new multi-coupling multi-core cable damage monitoring method is designed to realize the damage judgment and location identification.This paper mainly studies the following work:Firstly,the propagation of ultrasonic guided wave in the structure of multi-core cable is analyzed,and the excitation and sensing mechanism of ultrasonic guided wave is studied.The basic principle of piezoelectric effect of piezoelectric element is described briefly,the monitoring principle of electromechanical impedance technology and the mechanism of electromechanical coupling are analyzed.Secondly,the damage monitoring of multi-core cable structure is studied in detail,the damage monitoring mechanism of coupled multi-core cable structure is analyzed,the coupled electromechanical impedance technology and coupled ultrasonic guided wave technology are studied,the multi-coupled multi-core cable damage monitoring method is designed,and the multi-coupled excitation sensor array is analyzed.By using ABAQUS finite element analysis software,the multicore cable structure model is established,and the simulation is verified based on the assembly model.Considering the practical engineering application,the monitoring structure installation array is analyzed,and the circular single-side linear array connected in series sensor array is proposed.Third,coupled electromechanical impedance technology part.The impedance extraction method of the coupling structure after assembling the coupling mechanism array is analyzed,and the impedance value is extracted by voltage and current method to draw the admittance diagram.Experiments are designed to verify that when damage occurs,the amplitude and phase of the real admittance map change,and the damage measured at both monitoring points can be judged.When the distance between the damage and the monitoring point increases,the amplitude and phase changes in the real admittance plot increase.Both the simulated circumferential physical damage and the simulated adhesion defects can be judged by the change of the admittance real part diagram.When the damage degree deepens,the change of the real admittance map increases.When the damage quantity increases,the change of admittance real part graph increases.By constructing damage index RSDM to further quantify the damage,the admittance real part diagram can realize the preliminary judgment of the damage,but the damage analysis needs further research and analysis.Fourth,coupled ultrasonic guided wave technology.Further study and analysis of structural damage of coupled cable,propose the damage monitoring method and principle of coupled structural parts,generate guided wave by coupling mechanism,extract and analyze the echo signal by guided wave reflection method and ultrasonic probe,further analyze the excitation method,and propose a multi-point excitation method.The experimental results show that,under single point excitation,the amplitude of the excited main cable signal is large,but it is seriously coupled by the guide wave of adjacent cable wires,and the signal analysis cannot be carried out.The coupled guide wave propagates through the cable wire contact,and the received coupled guide wave signal is chaotic and the waveform is complex and unclear.Under the multi-point excitation method,the amplitude of the received signal increases,the waveform is clear,and the envelope is obvious,the cable contact guided wave coupling is obviously suppressed,and the signal-to-noise ratio is increased.The damage signal echo diagram under multi-point excitation is analyzed,and the relative damage position is calculated through the formula.The guided wave propagation speed in the multi-core cable structure is5545.29m/s,the relative damage position size is 152.39 mm,and the error is 1.59%.In this paper,based on giving full play to the advantages of electromechanical impedance and ultrasonic guided wave nondestructive testing methods,a coupling mechanism matching the structural characteristics of multi-core cables is designed and the two methods are actually applied to the structure of multi-core cables.By using the characteristics of electromechanical impedance technology with high local sensitivity,the dynamic damage changes are quickly judged,and the advantages of ultrasonic guided wave technology with wide detection range and high detection efficiency are combined.The damage location was studied.The experimental results show that the damage judgment of multi-core cable structure and the damage location on multi-core cable structure are realized,the cable where the damage is located is defined,the accuracy of damage location is improved,and the feasible path is provided for the indepth study of multi-core cable structural damage.At the same time,it also provides a new idea in the field of non-destructive testing and structural health monitoring of complex structures.