铁磁屏蔽对脉冲涡流检测的影响机理

针对脉冲涡流进行缺陷检测经常受到激励磁场和背景磁噪声干扰的问题,提出对缺陷处进行铁磁屏蔽的方法。在脉冲涡流检测中的磁屏蔽理论分析基础上,建立了脉冲涡流检测的有限元仿真模型。仿真表明:对于铁磁性构件,铁磁屏蔽能够使感应涡流尽可能地分布在缺陷附近,该措施减弱了检测信号的幅值,但对于不同深度的缺陷能够更好的辨别,能有效提高缺陷检测的灵敏度。根据有限元仿真结果,制作了铁磁性材料的磁屏蔽罩。实验表明:在铁板的表面,铁磁屏蔽能有效提高其检测信号灵敏度,而在铁板亚表面,灵敏度获得的提升较小。

Investigation of the Mechanism of the Influence of Ferromagnetic Shielding on Pulsed Eddy Current Testing(PECT)

Aiming at the problem that eddy current signal was easily disturbed by the excitation magnetic field and background magnetic noise, the method of PECT based on ferromagnetic shielding was proposed. The finite element simulation model with ferromagnetic shielding was established on the base of the theoretical analysis of magnetic shielding. The simulation result showed that the component of eddy current became intensive under the ferromagnetic shielding, although it weakened the amplitude of the testing signal. The defects of different depth can be easily recognized and the sensitivity of signal is effectively improved. According to the results of finite element simulation,the magnetic shield of ferromagnetic materialis manufactured. The experimental result indicates that magnetic shielding can effectively enhance the sensitivity of testing on the surface defects of ferromagnetic metal, whereas the method cannot improve the detection effect on the subsurface defects of ferromagnetic metal.