| In recent years,rail transit and railway construction is increasing in China's urban.Shield machine has become an indispensable and important equipment for road traffic construction and resource devel.While the working environment of the shield machine is bad,the main tool hob of the rock breaking is worn quickly and the hob is expensive.Once the tool ring could not work,it needs to be replaced in time.Otherwise,the damage of the hub and bearing can be caused,and the efficiency of construction will bring more damage to the project.At present,the main method of hob wear detection is based on the experience of construction personnel and shut down inspection,which means hidden dangers are still exist and also affect the efficiency of construction.So the designation of worn detection system of shield machine hob is particularly important to us.In this paper,eddy current sensor is applied to detect the worn status of the cutter blade of shield machine.As an important method of modern nondestructive testing technology,eddy current detection technology has the advantages of high sensitivity and fast response in displacement measurement,and the mud,foam in the construction environment of shield machine will not affect the detection effect.For the wear detection problem of the hob cutter of the shield machine,this paper theoretically analyzes the application of the eddy current sensor in hob wear detection,performs finite element simulation on the hob wear detection system,and sets up an experimental platform for hob wear detection system.The 19-inch hob cutter ring wear test was completed.This paper summarizes the failure modes of shield hob wear.According to the principle of eddy current testing,the distribution range of vortex on the surface of hob cutter ring is analyzed.It provides a theoretical basis for the design of hob wear detection system of shield machine.The project uses COMSOL simulation software.The hob cutter model and the eddy current coil model were established.The effects of the excitation frequency,the inner diameter of the eddy current coil and the number of turns on the magnetic field distribution and the coil impedance of the knife circle in the hob wear detection were simulated.The design of the sensor was optimized based on the simulation results.The project produced eddy current sensor probes,using the front-end in the laboratory and data acquisition card to build the lower computer.Using LabVIEW to design PC software to realize real-time display and recording of wear;to detect the same hob by sensors with coils of different shapes,and to analyze the output voltage value by changing the distance between the sensor probe and the knife ring,and to realize the most of the probe shape.Excellent design;through the detection of different wear of the hob cutter circle,to fit the relationship between the output signal of the hob wear detection system and the actual wear amount,to achieve the calibration of the hob wear detection system,and the detection of the hob cutter ring wear.Shield machine hob wear detection system is used to verify the detection effect of different shapes of the coils.The experiment verifies that the shield hob wear detection system of the circular probe has a higher linear range than the output voltage of the elliptical probe and has high sensitivity;Knife wear calibration experiment,using regression analysis to obtain the relationship between the amount of wear and output voltage,to achieve a static calibration of the detection system,using regression analysis to obtain the relationship between wear and output voltage.Theoretically,the system sensitivity can reach 0.25V/mm with a resolution of 0.0012 mm.For the wear detection of the 19-inch hob,the maximum absolute error of the detection system is 0.25 mm,and the maximum relative error is 8.6%.The experimental results show that the worn detection system of the shield cutter can accurately and reliably reflect the worn state of the hob and provide a strong basis for replacing the cutter ring. |
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