Based on the spatial distribution of magnetic dipole,the equation of the normal component of leakage magnetic field on the tube surface under low-intensity field was derived.

• 根据磁偶极子空间磁场分布,导出了在外部垂直方向弱磁场下管状工件表面细长缺陷产生的弱磁场法向分量的计算公式。