65Mn钢板电镀镍层厚度的增量磁导率检测方法

Magnetic Incremental Permeability Detection Method for Measuring the Thickness of Nickel Layer of 65Mn Steel Plate

针对铁磁性构件表面的铁磁性镀层测厚问题,提出利用增量磁导率检测方法,同步获取多种有效磁参量对镀层厚度进行无损表征.采用镀镍的65Mn钢板作为检测试样,对不同试样中检测得到的高低频叠加磁场响应信号进行滤波分离、正交解调等处理,最终提取出切向磁场、涡流阻抗和增量磁导率曲线中的多项特征参量.采用线性拟合方法对比分析了多项磁参量对镀层厚度的表征效果(线性相关程度和归一化灵敏度),选取出重复测试分散性小、归一化灵敏度高的磁参量,实现了65Mn钢板表面镀镍层厚度的良好检测.

Magnetic incremental permeability detection method was investigated to resolve the problem of measuring the thickness of ferromagnetic layer on the ferromagnetic component surface.During the incremental permeability detection process,a variety of magnetic parameters were measured and applied for non-destructive characterization of layer thickness.Nickel-coated 65Mn steel plates were used as test samples.Digital filtering tool was employed to separate the concerned signal from the measured magnetic responses superimposed by low and high frequency components.Orthogonal demodulation together with related digital signal processing techniques was used to extract multiple magnetic parameters from the curves of tangential magnetic field,eddy current impedance and magnetic incremental permeability.Linear fitting method was used to evaluate the performances(represented by the linear correlation extent and normalized sensitivity)of individual parameter on characterizing the nickel layer thickness.The magnetic parameters with small dispersion for repeated test results and high normalization sensitivity were selected for high-performance nickel layer thickness measurement on 65Mn steel plate.