Fundamental Research On Material Detection Based On Eddy Current Effect Of Intrinsically Flexible Coil

Material detection is of great significance in the fields of industrial manufacturing,aerospace,national defense and military.In modern engineering practice,many applications require material detection sensors to work in a bent state.Therefore,the sensor needs to be flexible to ensure that it can be covered on the curved surfaces compliantly to complete the task of the material detection.In this dissertation,an intrinsically flexible coil made of carbon nanotube-filled silicone rubber composite is designed and fabricated,the sensitive characteristics of the intrinsically flexible coil impedance to the target-material-type is studied preliminarily,and the material detection method based on the ratio interval is designed.The main works of the dissertation is:(1)Based on the tunnel effect theory and the electromagnetic induction theory,the mechanism of the eddy current effect of the intrinsically flexible coil is analyzed;the intrinsically flexible coil samples made of carbon nanotube-filled silicone rubber composite are designed and prepared.Their mass ratios of the conductive phase to the matrix phase are0.1,0.2,0.3,and 0.4,respectively;And the material detection experimental platform is designed and build to lay the foundation for subsequent research.(2)By analyzing the sensitive characteristics of the intrinsically flexible coil impedance to the target-material-type,the following conclusions are drawn: the impedance amplitudes and the impedance angles of the intrinsically flexible coils with different mass ratios under different target-material-types decrease monotonically with the increase of the lift-off.The linear correlation characteristics between the equivalent reactance and resistance of the intrinsically flexible coil under different material targets are different;when the mass ratio is 0.2 and the excitation frequency is 100 k Hz,the average goodness of fit for each material target is the largest,which is 0.937.(3)The material detection method based on the ratio interval is designed: within the effective detection distance,the ratio intervals of the imaginary and real parts of the impedance change corresponding to each material do not overlap each other.Regarding the ratio of the imaginary and real parts of the impedance change as the characteristic quantity,the material type of the target can be detected.By analyzing the effective detection distance,the material detection range and the non-overlapping degree of the intrinsically flexible coil,the following conclusions are drawn: when the mass ratio is 0.2 and the excitation frequency is 100 k Hz,within the effective detection distance of 0～2mm,the intrinsically flexible coil can detect the materials of copper,titanium alloy(TC4)and iron-nickel alloy(1j85)with the maximum non-overlapping degree of 0.045.The aforementioned research results preliminarily verify the feasibility of using intrinsically flexible coils for material detection,and lay a foundation for the development of the material detection sensor with intrinsic flexibility.77 figures,22 tables,52 references...