涡流效应影响高速运动钢管磁化的仿真研究

根据楞次定律，在高速漏磁检测过程中钢管与轴向磁化线圈发生轴向相对运动时将产生涡流效应。涡流磁场与原磁化场叠加后影响钢管磁化状态，最终影响到高速漏磁检测结果的一致性。为分析高速漏磁检测中涡流效应对钢管全长磁化的影响，将原磁化场矢量分解轴向分量和径向分量并根据楞次定律建立钢管内部涡流分布方程，并获得感应涡流磁场在钢管中的空间分布。分析涡流磁场叠加于原磁化场之后对管头、管体和管尾处磁化状态的影响，发现管头涡流磁场与原磁化场方向相反，涡流效应具有抑制钢管磁化作用；管尾处两者方向相同，涡流效应具有增强磁化作用；涡流效应对管体磁化基本没有影响。通过有限元法分析钢管运行速度与涡流密度的关系，并进一步研究涡流效应对钢管管头、管体和管尾磁化状态的影响，为钢管全长一致性评价提供参考依据。

Numerical Simulation on the Influence of the Eddy-current Effect on the Magnetization of Steel Pipe at High Speed

According to Lenz’s Law, eddy current effect essentially occurs when relative movement happens between steel pipe and axial magnetizing coil in magnetic flux leakage(MFL) testing. The eddy current magnetic field and the magnetizing field magnetize the pipe together, eventually affecting consistency of the MFL signals. The aim is to analyze the affection on the pipe magnetization by eddy-current effect. Firstly, the eddy current distribution equation in the pipe is established based on the Lenz’s Law, and moreover the eddy current magnetic field is obtained. Then, the eddy current magnetizing affections on the pipe head, pipe body and pipe tail are analyzed respectively. The direction of the eddy current in the pipe head is opposite to the one of the magnetizing current, which brings about the reduction of magnetization status. However, the eddy current in the pipe tail and the magnetizing current have the same direction, resulting in the increase of the magnetization. For the pipe body, the eddy current has no affection on the magnetization. The finite element simulation was applied to analyze the relationship between the eddy current intensity and the pipe moving speed and the affection of the eddy current on the magnetization of the whole pipe, which supplies the reference of the uniform evaluation for the steel pipe.