This paper decomposes the sorts of tubing defects into three types of single defect, namely pit-like, through-hole and strip-like defect, as well as compound defects formed by the superposition of the above three types of single defect. Then the 2D finite element method was used to model the tubing with different defect types, and the variation of MFL caused by the change of width, depth and other parameters of a single defect is simulated and analyzed, and the corresponding quantitative relationship curve and fitting formula are obtained. Then the superimposed defects and the compound defects of the same side and the opposite side were simulated to obtain the quantitative relationship curve between the magnetic flux leakage of the compound defects and the width, depth or distance between adjacent defects. Finally, Based on the comparative analysis of the influence pattern of compound defects and single defect, the quantitative pattern of MFL detection is summarized. Simulation results show that the variation of magnetic flux leakage between single defect and compound defects with different defect parameters is similar. The MFL detection signal of compound defects is also affected by the location relationship of adjacent defects and changes regularly. Based on this rule, and further combined with the study of transient field, more comprehensive and accurate defect parameters and the density of compound defects can be obtained, so as to better meet the high requirements of non-destructive evaluation.

本文将各类管材缺陷分解为坑状、通孔和条状缺陷三种单一缺陷，以及上述三种单一缺陷叠加形成的复合缺陷。然后采用二维有限元方法对不同缺陷类型的油管进行建模，模拟分析单个缺陷宽度、深度等参数变化引起的MFL变化，并得到相应的定量关系曲线和拟合公式得到。然后对叠加缺陷和同侧和对侧的复合缺陷进行模拟，得到复合缺陷的漏磁与相邻缺陷的宽度、深度或距离之间的定量关系曲线。最后，通过对复合缺陷和单一缺陷影响模式的对比分析，总结了MFL检测的定量模式。仿真结果表明，具有不同缺陷参数的单缺陷和复合缺陷之间漏磁通的变化相似。复合缺陷的MFL检测信号也受相邻缺陷位置关系的影响，有规律地变化。基于此规律，进一步结合瞬态场的研究，可以获得更全面、更准确的缺陷参数和复合缺陷的密度，从而更好地满足无损评价的高要求。仿真结果表明，具有不同缺陷参数的单缺陷和复合缺陷之间漏磁通的变化相似。复合缺陷的MFL检测信号也受相邻缺陷位置关系的影响，有规律地变化。基于此规律，进一步结合瞬态场的研究，可以获得更全面、更准确的缺陷参数和复合缺陷的密度，从而更好地满足无损评价的高要求。仿真结果表明，具有不同缺陷参数的单缺陷和复合缺陷之间漏磁通的变化相似。复合缺陷的MFL检测信号也受相邻缺陷位置关系的影响，有规律地变化。基于此规律，进一步结合瞬态场的研究，可以获得更全面、更准确的缺陷参数和复合缺陷的密度，从而更好地满足无损评价的高要求。