Design Method And Experiment Of Magneto-elastic Cable Tension Sensor

Cable has become increasingly widely used in various civil infrastructure and large construction structures. As the main load-bearing components, Structure linear, internal force distribution, load, attenuation, failure, and even the structural safety of the cable focus on the overall performance of the cable force. In order to master cables'r working condition and structural safety, to detect incidents timely and to prevent the sudden accident, the cable tension must be long-term online monitored.Magneto-elastic cable force sensor has been used on some bridges because of its advantages of long life, low cost, easy replacement and almost no effect on cable. The non-closed magnet circuit sensor is the only kind of sensor who has been used. There were little relevant reports about the design of this kind of sensor. Magnetic conductors are combined to cable in closed magnetic circuit structure sensor, which may facilitate the transmission of the magnetic field. So the performance of this type of sensor may be better than the non-closed magnetic sensors. But the design and experiment of this kind of sensor needs to be further carried out. So in order to promote the development of magneto-elastic cable forces sensor, and to provide technical support for engineering applications, the main contents are as follows:①The basic principle is discussed combined with non-closed magnet circuit sensor. Analysis of sensor's impact elements shows that material properties of cable and magnetic distribution in sensor will affect measurement accuracy.②The material properties of cable's magneto-elastic effects were studied by experiment in the case of little readily available research results which could be referenced. After processing the experimental data, some magneto-elastic parameters of cable such as magneto-elastic coefficient, permeability, etc are identified preliminary. The measurement principle is further improved combing with those parameters and the simulation analysis are carried out.③Demagnetization field and motivate magnetic field are analyzed. Theory and related experiments show that the non-uniformity of magnetic field distribution inside the sensor will generate impact on the sensitivity, linearity and repeatability.④Design method of magneto-elastic cable tension sensor is investigated from cable, coils, magnetic field, signal and other aspects. Specific method and guideline of magneto-elastic cable tension sensor's parameter calculation are proposed, which can guarantee uniform magnetic field in cable, coils'safe excitation, improving the sensitivity and the signal to noise ratio, et al. The sensors'operating point is optimized according to the material characteristics of cable material's magneto-elastic effect. Various types of sensor used for single wire(φ7mm ) cable are designed, and the tensile experiments are carried out. Results show that experimental results are qualitative consistent with principle of magneto-elastic measurement, with good reproducibility and higher sensitivity indicating that the design of sensor achieve the desired requirements. Comparing the experimental results of various types of sensors shows that closed circuit sensor (except for double-bypass outside) have higher sensitivity and reproducibility than the non-closed magnetic sensors. Finally, the non-closed magnetic sensor'loading experiment on a practical application cable is carried out and the results show that the sensitivity is -0.3535mV/MPa, linear fit coefficient 0.9973. This design method is feasible.