Selection of Radial and Axial Components from Magnetic Flux Leakage Signals
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摘要: 缺陷漏磁场的径向分量和轴向分量是漏磁检测中经常检测的物理量, 两者之间如何选择, 至今尚无定论。采用等效面偶极子模型分析了缺陷漏磁场的空间分布特点, 解释了径向分量比轴向分量衰减更快的原因。结合有限元方法, 研究了不同深度、宽度的二维矩形槽和不同倾角的梯形槽缺陷的漏磁场分布, 分析了径向分量与轴向分量的变化特点, 总结了缺陷参数变化时临界点的变化趋势。从探头设计的角度, 考察了探头提离值以及缺陷参数对缺陷漏磁场信号轴向和径向分量幅值的影响, 提出利用临界点作为检测分量的选取原则。Abstract: Both radial component and axial component are the favorite testing factors in the magnetic flux leakage testing(MFLT). Equivalent magnetic dipole model was taken to analyze the distribution feature of magnetic flux leakage of defects, demonstrating the fact that radial component decays more rapidly than axial component. The flux leakage due to steel pipe defects with various defect depth(10% to 40%) and width(0.5 mm to 20 mm) was calculated using finite element method. The sharpness angle of the notch was also taken into consideration in the calculation. The critical point, where the amplitude of radial component is equal to that of axial component, transits with various parameters of defects. The tendency of shift of critical point is discussed for the different cases. The effects of lift-off of sensor and defect parameters on amplitude of components of flux leakage were studied from sensor design. The conclusion is drawn that critical point can be used to determine which component would be pick out by one dimensional sensor in designing MFLT equipments.
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Keywords:
- Magnetic flux leakage testing /
- Axial component /
- Radial component /
- Critical point
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