基于微分磁导率的铁磁性材料无损检测新方法

New NDT method for ferromagnetic materials based on differential permeability

利用微分磁导率变化特性,提出了一种可对材料的宏观缺陷进行快速扫查的无损检测新方法。首先,将铁磁性材料置于偏置磁化场环境下,缺陷将导致内部磁通的畸变;其次,磁通畸变进一步体现在材料表面微分磁导率分布的差异性;再次,通过特殊设计的微分磁导率检测探头,对材料表面微分磁导率的分布进行扫查;最后,由磁导率分布差异获得材料内部的不连续性信息,从而实现对缺陷的无损检测。开展了系列验证实验,结果表明,相对于传统的漏磁检测方法,新方法具有磁化强度低、磁通泄漏少、检测信号稳定的特点。新方法正、反面缺陷探测信号存在差异,在缺陷深度识别方面亦存在优势。

A new non-destructive testing method is proposed to fast scan and detect the macroscopic defects of materials using the variation characteristics of the differential permeability of ferromagnetic materials. Firstly, the ferromagnetic material, such as steel plate, is placed under the bias magnetic field, and the defects in the material will inevitably lead to the distortion of its internal magnetic flux. Secondly, the magnetic flux distortion is further reflected in the difference of the differential permeability distribution on the surface of the tested material. Thirdly, using a specially designed probe, the distribution of differential permeability on the surface of tested material is rapidly scanned. Finally, from the difference of the differential permeability distribution, the discontinuity information in the material can be obtained, so as to realize the nondestructive testing of macroscopic defects. Series of experiments were carried out, and the results show that, compared with traditional magnetic flux leakage method, the new method has the advantages of low magnetic intensity, less flux leakage and stable detection signals. Moreover, the detection signals for the front-side and back-side defects have obviously different distribution characteristics, and the method also has obvious advantages in the field of defect depth identification.