Array Eddy Current Nondestructive Testing System Based On Spin Sensing And Magnetic Shielding Structure

Nondestructive testing is the method to detect the physical and chemical properties of specimens as well as the morphology of the test piece.It mainly uses electric,magnetic,sound,light,ray and other means.With the development of modern industry,nondestructive testing has become an important testing method for product quality control and quality assurance.Firstly,this paper introduces five nondestructive testing methods: ultrasonic testing,radiographic testing,magnetic particle testing,penetrant testing and eddy current testing.Eddy current testing has developed rapidly in the field of nondestructive testing because of its advantages of non-contact,no damage to the tested parts and fast response time.At present,eddy current testing mainly adopts conventional multiple scanning method,which has a slow detection speed.Array eddy current nondestructive testing method can be used to ensure the detection accuracy and greatly improve the detection efficiency.However,mutual inductance crosstalk exists in array eddy current nondestructive testing,and its quantitative detection accuracy is not high.At the same time,the defect information is obtained mainly through the analysis of detection data,and the real-time intuitive display is not realized.In order to solve the problems in the conventional array eddy current nondestructive testing,this paper uses a high sensitivity spin valve sensor chip as a sensitive element to detect the eddy current magnetic field changes caused by the defects of the test piece,which improves the detection sensitivity.Adding array structures to improve the scanning range of system single detection.The magnetic shield structure is used to eliminate the signal crosstalk between adjacent eddy current probe units,and improve the detection accuracy.Through the upper machine real-time imaging,intuitive display of detection results.In this paper,Ansoft Maxwell software is used to simulate and optimize the structure and size parameters of eddy current probe unit,and analyze the mask effect of mutual inductance crosstalk between adjacent probes by simulation.Combined with the simulation results,a new array eddy current nondestructive testing system is designed.The system uses AD9850 direct frequency synthesizer and TDA2030 A power amplifier to build the signal generation circuit,and uses the spin valve sensor chip to directly extract the eddy current magnetic field changes caused by the defects of the tested parts.Finally,the output signal of the sensor chip is collected in real time by the data acquisition card,and the LabVIEW program is written for real-time imaging display.Finally,the feasibility of the system design method and the accuracy of simulation are verified by testing.Experimental results show that the designed array eddy current probe can effectively improve the detection accuracy and efficiency,and the inversion calculation model is obtained by establishing the corresponding relationship between the defect depth and the difference peak value,and the inversion error is less than 3%.By analyzing the data collected with or without magnetic shielding and the real-time imaging results,it is verified that the magnetic shielding structure can effectively reduce mutual inductance crosstalk in the array eddy current probe.The test results show that the system is reliable and has wide application prospect in the industrial field.