磁化方向对焊缝缺陷漏磁场的影响分析

漏磁检测（MFL）技术适用于焊缝裂纹、气孔等缺陷的检测。由于焊缝结构的特殊性，不同磁化方向下的磁化路径及漏磁场强度均存在差异。采用合适的磁化方向能够激发更强的缺陷漏磁场信号，从而提高小尺寸缺陷的检出率。通过Ansys有限元仿真软件计算焊缝缺陷漏磁场，定量分析比较了磁化方向分别为垂直与平行于焊缝时，圆孔缺陷和纵向矩形槽缺陷的漏磁场及其分量强度。据此探讨任意磁化方向下的缺陷漏磁场及分量的特征规律，并搭建了焊缝漏磁检测平台进行试验验证。实验结果表明，圆孔型缺陷垂直磁化时漏磁信号幅值仅为平行磁化时的18.6%，纵向裂纹型缺陷平行磁化时漏磁信号幅值仅为垂直磁化时的9.2%至29.3%。

Analysis for MFL Signal of Weld Defects Affected by Magnetization Direction

Magnetic flux leakage (MFL) technology is suitable for weld crack, porosity and other defects testing. Due to the particularity of weld, magnetization paths and MFL signals under different magnetization directions are different, and adopting appropriate magnetization direction can stimulate stronger MFL signals, thus improving the detection rate of small size defects. Ansys FEM simulation software was used to calculate the MFL signals of weld defects, and the strength and components of the MFL signals of circular holes and longitudinal rectangular slots defects when the magnetization direction was perpendicular or parallel to the weld seams were respectively analyzed and compared quantitatively. On this basis, the variation rules of the MFL signals in different magnetization directions were discussed. A MFL testing platform for welding seams was established for experimental verification. The experimental results show that the magnetic flux leakage signal amplitude of circular flaw is only 18.6% of that of parallel magnetization, and the magnetic flux leakage signal amplitude of longitudinal flaw is only 9.2% to 29.3% of that of vertical magnetization.