Study On Magnetostrictive And Elastomagnetic Based Sensor Integration Technology For Applications In Steel Wire Rope Inspection

Steel wire rope is commonly used in special equipments and civil engineeringsfor its superior property of high tensile strength and poor performance in bending andshear. The application examples of wire rope include the cable in suspension bridgeand passenger ropeway, the hoist wire rope in lift and elevator, etc. The wire ropesserve as the most important bearing parts in the structures, their health conditiondirectly affect the operation safety and service life of the whole structure. Corrosionsor fractured wires occurred in the wire rope due to the complexity in stress state anddiversity of service environment may result in a reduction in the load-carryingcapacity of the structure that can lead to collapse even major accidents and loss.Therefore, the development of new integrated techniques for defect detection andtension measurement of the wire rope has significant social and economic value.This paper is dedicated to the development of integrated sensor technology forwire rope defect detection and tension measurement based on the magnetostrictiveand elastomagnetic effect of ferromagnetic material. First, the computational modelfor revealing the amplitude-frequency characteristic of the magnetostrictive sensor(MsS) is established.This computational model together with the electromagnetic fieldfinite element simulation method is applied for the optimization of the structural andworking parameters of the integrated sensor. Second, an innovative flexible printedcoil (FPC) is designed and manufactured for the MsS to replace the traditional hardsolenoid coil and enhance the performace in exciting and receiving guide wave energy.Finally, the proposed integrated sensor is applied for experimental study on theattenuation characteristics of longitudinal guided waves in wire rope, detecting defectsand measuring tension level of the wire rope. This paper focuses on the detectionmechanism analysis, optimal sensor design and experimental research on theinspection techniques for wire rope health monitor, the main research contentsinclude:(1) A computational model for revealing the amplitude-frequency characteristicof the MsS is established in consideration of the coupling between electromagneticfield and ultrasonic waves. The influence of the sensor structure parameters on theexcitation and receiving performance of MsS is analyzed through the computation ofmagnetic field distribution inside the circular electric current and multiple groups ofsensing coil. Then, the amplitude-frequency characteristic curves of the transmitterand receiver MsS are derived from the signals that are simulated based on weight andphase superposition principle. The obtained conclusions provide fundamental basisfor the parameters design of the MsS.(2) An innovative flexible printed coil-based MsS with superior performances is designed for the application in the high and low frequency range. The flexible printedsensing coil is embedded into a light and thin film which can be wrapped onto thewire rope surface, so that the FPC can be easily installed onto and dismounting fromthe rope. The experimental results show the FPC has superior detection performanceand its working frequency can reach from tens of kilohertz to megahertz range.(3) An integrated sensor with dual mode is designed and its working parametersare optimized. The integrated sensor can work on dual mode of MsS andelastomagnetic sensor (EMS) with functions of both defects detection and tensionmeasurement. The sensor can detect the defect in the rope based on guided wavetechniques and measure the tension based on the elastomagnetic method. In addition,the bias magnetic circuit of the integrated sensor is optimized in consideration of boththe energy conversion efficiency and the tension measuring sensitivity of the sensor.(4) The phenomena of frequency band missing and shifting of L (0,1) mode inwire rope under tension loading are observed. The developed integrated sensor in thispaper is used to measure the notch frequency band of L(0,1) mode in seven-wire steelstrands and6×19S-FC wire ropes, the measured central frequency of the notchfrequency band is around70kHz and it increases as the increase of tension force. Thespectrum energy of the L(0,1) mode in a6×29FI+IWR wire rope will shift from100kHz to30kHz when the tension force is increased.(5) The performances on defect detection and tension measurement of theintegrated sensor are calibrated. First, the integrated sensor works on the MsS mode todetect the broken wire flaws in the wire rope. The experimental results show that theMsS can receive the signal reflected from four broken wires and successfully detectthe four broken-wire flaws that locate apart from the sensor less than two meters.Second, the integrated sensor works on the EMS mode to be applied for tensionmeasurement in wire rope. The experimental results obtained from a seven-wire steelstrand shows that the stress measurement resolution of the sensor is less than10MPa.