Development Of Water Detection System For Cables Based On Magnetostrictive Guided Waves

As the main load-bearing structure of cable-supported bridges,the cables work in harsh outdoor environments for a long time,and the internal water may cause corrosion of steel wires due to seal failure,which endangers the operational safety of the bridge.Aiming at the problem of detection of accumulated water on cables in service,this paper develops a detection system for accumulated water on bridge cables based on magnetostrictive guided wave technology,which provides support for the detection of accumulated water on bridge cables and the prevention of corrosion.First,based on the finite element model analysis method,the propagation characteristics of guided waves of parallel steel cables are studied.Based on the structural characteristics of parallel steel cables,the parallel steel cables with small torsion angles are approximated as structures with constant cross-sections,and a model analysis model is established based on the cross-sectional structure of cables.The dispersion curve and cross-sectional mode shapes of the cable are obtained by solving the model,and the propagation characteristics of the guided wave are obtained by using the solved results,and the optimal excitation parameters for the guided wave detection of water accumulated in parallel steel wire cables are determined.The experiment carried out on the sample cable verifies the correctness of the model calculation results.Then,based on finite element simulation and experiment,the guided wave detection mechanism of cable water was studied.According to the elastic wave reflection and transmission characteristics under the solid-liquid interface,combined with the cross-sectional mode shapes,the reasons for the attenuation of the guided wave caused by the water accumulation are analyzed;the finite element simulation model of the cable with accumulated water is established,and the characteristics of the water accumulation are extracted according to the simulation results parameter.Subsequent water guided wave detection tests were carried out with steel wires,steel strands and cables as objects,which verified the correctness of the detection mechanism.Finally,a magnetostrictive guided wave detection system for the detection of accumulated water in bridge cables is designed.According to the requirements of guided wave detection of accumulated water in cables,the parameters that the detection system should reach are analyzed.Aiming at the design ideas of modularization,miniaturization and strong applicability,a signal generation and acquisition unit that meets the requirements of guided wave detection was selected,and the power supply module,power amplifier module,and signal processing module were designed and fabricated.Assembly of the system was completed.and carried out the performance and cable water detection test of the system.The inspection system was used to carry out the bridge cable field inspection test,and the test was consistent with the results of the window verification.