运动感应涡流磁场检测中的激励磁场优化设计方法

Optimization design method of excitation magnetic field in motion induced eddy current magnetic field testing

在生产或使用过程中,薄金属板中会产生微缺陷(微颗粒或气孔),这些微缺陷的数目及尺寸决定了薄金属板的品质,影响其使用寿命和安全系数.因此,对微缺陷进行定量和准确的表征是保证薄金属板产品品质与使用安全的必要条件.电磁检测中的运动感应涡流磁场检测可应用于检测导电非导磁材料中的缺陷.本文通过模拟和实验结果显示,当提离距离、永磁体表面剩磁确定时,永磁体尺寸与缺陷检测信号幅值正相关.另外,提出一种运动感应涡流磁场检测中激励磁场的优化方法,由该方法产生的两种永磁体阵列相比于同体积、同表面剩磁的简单永磁体,产生的缺陷检测信号幅值更高,因而可以提高检测的灵敏度.

In the process of production or long-time use of a thin metal plate,micro defects(micro particles or pores)will be produced in its interior.The number and size of these micro defects determine the quality of the thin metal plate,affecting its service life and factor of safety.Therefore,quantitative and accurate characterization of micro defects is a necessary to ensure the quality and safety of thin metal plate products.In this work,we study the application of motion induced eddy current magnetic field testing in electromagnetic testing to detect defects in conductive material and nonmagnetic material.The simulation results show that when the lift-ff distance and the surface remanence of the permanent magnet are determined,the size of the permanent magnet is positively correlated with the amplitude of the defect detection signal.The main reason is that in a motion induced electric field without defects,the amplitude of defect detection signal is linearly related to the current density mode at each point on the defect motion path.Increasing the size of the permanent magnet can effectively improve the current density mode.As a continuation of the above results,an optimization method for excitation magnetic field in motion induced eddy current magnetic field detection is proposed.The two types of permanent magnet arrays generated by this method generate larger amplitude defect detection signals than that by simple permanent magnets with the same volume and surface residual magnetism.The experimental results show that the excitation magnetic field arrangement designed by the above optimization method increases the signal amplitude by 80%-90%compared with that by traditional method.This optimization method conduces to improving the sensitivity of motion induced eddy current magnetic field detection methods.