Sensor Design And Experimental Researchbased On Permeability Detectiontechnology

The permeability detection technology is studied in the paper,which is based on the electromagnetic induction principle that the induced voltage in the closed magnetic circuit of the probe is proportional to the rate of change of the magnetic flux to detect the permeability change of the sample.It is a new electromagnetic non-destructive testing technology that can be used to evaluate and detect microstructural changes such as stress concentration,fatigue damage,structural phase transition and aging metamorphism of ferromagnetic components.In this paper,firstly,combined with the theory of permeability detection,the high-sensitivity detection sensor is designed by means of experimental research.Finally,the permeability detection technology is applied to the stress concentration,fatigue damage,heat treatment quality and performance evaluation of ferromagnetic materials.It is of great significance to promote the application of permeability detection technology in engineering.Taking 45#steel plate as the research object,the constant voltage source and the constant current source was used as the excitation source respectively,and the relationship between the detection sensitivity and the excitation frequency and amplitude,the number of turns of the coil and the cross-sectional area of the winding was studied.Taking the 430ferritic stainless steel specimen as the research object,the constant voltage source was used as the excitation source,and the relationship between the optimal excitation frequency and the excitation voltage amplitude,the number of turns of the coil and the applied tensile stress was studied,and designed a high-sensitivity detection sensor,built a high-sensitivity detection technology platform.When the constant voltage source is used as the excitation source,The research results show that within the range of excitation signal frequency adjustment,there is a maximum value of the detection sensitivity of the system,which is the optimal frequency of the detection system;The detection sensitivity of the system and the voltage value of the AC excitation signal increase linearly;The detection sensitivity of the system increases linearly with the number of turns of the detection coil.The more the number of detection coil turns,the higher the detection sensitivity of the system,and with the increase of the number of turns of the excitation coil first increases and then decreases;The detection sensitivity of the system is positively correlated with the cross-sectional area of the excitation coil,regardless of the cross-sectional area of the detection coil.When the constant current source is used as the excitation source,the research results show that the detection sensitivity increases first,then decreases and then increases with the increase of frequency,and finally tends to a fixed value,and there are two extreme values,that is,there are two optimal frequencies;it increases with the increase of sinusoidal AC excitation current,and shows a linear relationship;it increases first with the increase of the number of turns of the excitation coil and then approaches the constant,and the optimal frequency shifts to the short frequency;it increases linearly as the number of turns of the detection coil increase.The optimal detection frequency decreases with the increase of the number of turns of the excitation coil,and is independent of the number of turns of the detection coil and the amplitude of the excitation voltage,and does not change with the number of turns of the detection coil and the amplitude of the excitation voltage;the optimal detection frequency is related to the external tensile stress.When it exceeds the elastic deformation stage of the test piece,the optimal frequency increases with the increase of tensile stress,and the growth rate is slow in the late stage of uniform plastic deformation.Taking 45#steel plate as the research object,test sensor parameter optimization results:set the excitation parameters to U=5V,f=300Hz,the excitation coil winding cross-sectional area is0.0628mm~2,the number of turns N=300,the detection coil winding cross-sectional area is0.01766mm~2,the number of turns N=400;The excitation current value I=0.1App,f=1000Hz,the excitation coil winding cross-sectional area is 0.0628mm~2,the number of turns N=400,the detection coil winding cross-sectional area is 0.0314mm~2,the number of turns N=300.Taking the 430 ferritic stainless steel specimen as the research object,test sensor parameter optimization results:set the excitation parameters to U=5V,f=440Hz,the number of excitation coil turns N=200,the number of detection coil turns N=500,and the coil wire diameter is 0.2mm.Heat treatment and tensile test were carried out on 430 ferritic stainless steel.The relationship between permeability parameters and different annealing processes(annealing temperature,annealing time)and tensile residual stress was studied.The results show that the detection signal and material hardness increase first and then decrease with the increase of annealing time,and when the holding time is 30min,both appear extreme values;The detection signal decreases as the annealing temperature increases,and the material hardness increases as the annealing temperature increases;After annealing at 860?for 30min,the recrystallization of the structure is sufficient,the grain size is uniform and small,and the degree of equiaxification is obviously improved,and the comprehensive mechanical properties obtained are better.During the entire stress process of detection signal with the residual stress of the tensile force,for stress relief annealed 430 stainless steel components,the absolute signal change is 2.88V,and the relative signal variation is 40%;For 430stainless steel components at different annealing temperatures,the absolute change and relative change of detection signals are about 2.5V and 40%.According to the permeability detection technology,the quality of heat treatment on the specimens heat treated by different annealing methods can be evaluated,and the stress,residual stress state and fatigue damage state existing inside the ferromagnetic material can be sensitively detected,and the microstructure and mechanical properties of the component can be determined.