金属管件电涡流检测偏心效应的解析建模与仿真

Modeling and Analysis of the Effect of Probe Radial Offset on Eddy Current Nondestructive Testing and Evaluation of Metallic Tubes

电涡流方法是金属管道质量检测的一种有效手段,该方法要求探头和管道同轴。然而在实际工程应用中有很多干扰因素都会引起探头位置波动(即偏心),进而影响检测结果的精度和准确性。该文通过引入二阶矢量磁位,应用分离变量法建立了互感式探头偏心效应的解析模型;以此为基础仿真研究了不同材料、不同频率条件下偏心效应对探头信号的影响规律,并对偏心效应引入的误差进行评估。结果分析表明,偏心效应的阻抗变化近似为直线,且探头信号误差随着偏心量的增加显著增大,必须采取适当措施予以抑制。研究结果为研究偏心效应抑制算法提供了理论指导,有助于提高金属管道无损检测与评估的精度。

Eddy current testing is one of the most effective methods for the evaluation of metallic tubes.It theoretically requires perfect alignment of the axes of the tube and probe coil.In practice,however,alignment work can not be excellently performed or is impossible to carry out because of lack of space.As a result,probe response contains undesirable signal due to imperfect alignment（radial offset）,which readily degrades the SNR.In this paper,driver-pickup probe response is analytically modeled using Separation Method based on second order vector potential formulation.Next,simulations were done to analyze the effect of radial offset for different materials and exciting frequencies.The resulting errors were quantitatively examined.It is found that the impedance variation behaves like a straight line.The errors introduced increase with eccentricity of the probe,so techniques should be used to cancel out its effect.This research not only provides some help to develop algorithms for removal of the raidal offset effect,but also improves evaluation of the metallic tube.