铁磁构件内外表面裂纹低频漏磁检测技术研究

针对承压设备中铁磁性构件内外壁损伤检测问题,发展了一种低频漏磁检测技术。对低频漏磁信号进行分析处理,提取出的低频漏磁信号的幅值和相位信息,用于铁磁构件内外表面损伤检测与定量评价。通过数值仿真和检测实验,研究了裂纹深度和位置(上表面或下表面)的裂纹对漏磁场特征参数空间分布的影响。结果表明,漏磁信号的幅值特征参数和相位特征参数均可用于铁磁性构件上下表面一定深度范围内裂纹检测及定量表征,但两个参数对不同位置及深度范围内裂纹检测的敏感性不同。当裂纹位于试件上表面时,幅值特征参数对裂纹深度变化更敏感;而当裂纹位于试件下表面时,相位特征参数对裂纹深度变化的敏感性更高。本文研究工作为承压设备中铁磁性构件内外壁损伤检测做了有益探索。

Study on low frequency AC magnetic flux leakage detection for internal and external cracks of ferromagnetic structures

In this paper, based on the low frequency electromagnetic technology, the non-destructive testing of the internal and external surface of the ferromagnetic structures in the industrial pressure equipment is studied. By analyzing the magnetic flux leakage signal and the amplitude and phase change of magnetic flux leakage signal, a method for quantitatively characterizing the internal and external surface cracks of ferromagnetic structures is presented. Based on the low frequency magnetic flux leakage simulation model, the variation of the characteristic parameters of the magnetic flux leakage signal in different depth and different position is studied. Furthermore, a single channel low frequency magnetic flux leakage sensor is developed and applied to detect the internal and external surface of the ferromagnetic structure with different depth and different positions of the artificial crack. The simulation and experimental results show that the amplitude is more sensitive to the depth of the upper surface crack, and the phase value is more sensitive to the depth of the lower surface crack. This study provides technical support for the safe operation of the ferromagnetic structures of the industrial pressure equipment.