Design Of Eddy Current Array Nondestructive Testing System Based On ZYNQ

In the process of production and use of metal devices,under the complex process and stress environment,the metal surface will produce unavoidable defects such as corrosion,oxidation and crack,which will greatly affect the ductility,fatigue resistance and corrosion resistance of the metal.At this time,if the defects of the metal cannot be detected,the properties of the metal cannot be evaluated.Array eddy current testing is an improvement of ordinary eddy current testing.It is arranged around the tested metal specimen through the array eddy current probe.When a sinusoidal signal is supplied to the excitation coil,other coil arrays of the array eddy current probe,as the induction coil,will be affected by the alternating magnetic field generated by the alternating current of the excitation coil,so as to induce the induced electromotive force.The impedance information of the array coil is obtained by collecting the induced electromotive force of the array coil,At this time,the induced voltage needs to be I / Q decomposed,so as to use the measured metal object to obtain the changes of the real part,imaginary part and phase of the induced voltage signal of the array induction coil.Therefore,a set of array eddy current nondestructive testing system based on zynq is designed and verified by relevant experiments.The main work is as follows:(1)The principle of array eddy current testing is described in detail,the electromagnetic induction principle between the excitation coil and the tested metal is introduced,and the mathematical formula is given with the equivalent circuit to describe the relationship between them.For the 360 ° defect detection around the metal,an 8-channel array eddy current probe is designed,and the equivalent circuit between the excitation coil and the tested metal is expanded to illustrate the mathematical relationship between the multi coil array eddy current probe.(2)For the detection of metal defects,the spatial layout of array eddy current sensors is used to design the selection mode of excitation channel.At each moment,only one coil is the excitation coil,the other coils are the induction coil at this time,the other channel is the excitation coil at the next moment,and the other coils are the induction coil.This process is repeated.In order to cooperate with the array eddy current probe,a set of multi-channel array detection system is designed,which takes zynq-7000 as the core,uses its programmable advantages to flexibly control the sinusoidal excitation frequency given to the excitation coil,and uses the time-sharing multiplex switch to control the time-sharing excitation and time-sharing acquisition of multi-channel.(3)The mathematical formula of the digital phase sensitive detection algorithm to decompose the induced signal is deduced,and the digital phase sensitive detection algorithm is realized combined with zynq.The induced signal of the induction coil can be obtained through the digital phase sensitive detection algorithm,which is equivalent to the complex number and then decomposed into real part,imaginary part and phase.A digital filter is designed to filter out the specific high-frequency components,and finally the I / Q decomposition of the induced signal is completed.Aiming at the data interaction between upper computer and lower computer,TCP transmission and Lab VIEW upper computer modules are designed.