一种涡流检测探头响应与缺陷大小的关系研究

为了实现涡流无损检测的定量评估,设计了一种直接测量涡流磁场的涡流检测探头,该探头包含两个激励线圈和一个检测线圈.通过有限元法建立三维涡流仿真模型,对比研究导体内有无圆柱形缺陷时涡流的分布情况以及检测线圈响应的变化量.仿真结果显示,当导体内存在圆柱形缺陷时,涡流密度会集中分布在缺陷的侧面区域并且其大小会增加;检测线圈中响应的变化量与缺陷体积之间的关系满足两个指数函数的线性组合,对于体积较小的缺陷,检测线圈中响应的变化量与缺陷的体积近似成正比关系.实验结果验证了导体内存在小体积的缺陷时,检测线圈中响应的变化量与缺陷的体积之间的近似正比关系,证明了该结构的探头可以用于对缺陷的定量研究.

Research on relationship between response of an eddy current testing probe and defect

In order to realize the quantitative evaluation of eddy current nondestructive testing,an eddy current tes-ting probe which can be used to detect the eddy current field directly is designed. The probe is composed of two driving coils and a pick-up coil. With the finite element method,the three-dimensional eddy current simulation mod-el is established,and the distribution of eddy current and the changes in the pick-up coil response whether there is cylindrical defect in the conductor are compared and studied. The simulation results show that the eddy current den-sity will be concentratedin the side area of the defect and its magnitude will increase,when cylindrical defect exist-ing in the conductor. Meanwhile,the relationship between the changes in the pick-up coil response and the defect volume satisfy the linear combination of the exponential function. For smaller defects,the changes in the pick-up coil responseare approximately proportional to the volume of the defect. The experimental results show that there is an approximate proportional relationship between the variation of the response in the pick-up coil and the volume of the defect when there are small volume defects in the conductor. Consequently,it is proved that the structure of the probe can be used for the quantitative researchof defect.