时域电磁法套管探伤技术三维有限元数值模拟

提出了一种非接触式套管探伤装置设计方案.采用有限元仿真技术,对装置中纵向磁探头与横向磁探头的时域电磁响应进行了数值模拟.结果表明,纵向磁探头产生与套管同轴的环状涡流,而横向磁探头产生的涡流方向与前者互相垂直.磁探头上的接收信号主要来自金属套管.分析了套管上存在孔洞、纵向裂缝和横向裂缝时,两种磁探头的响应特性.不同孔洞损伤的电磁响应计算结果显示,两种磁探头对孔洞直径的变化均具有较高分辨率.通过对不同参数纵向裂缝与横向裂缝电磁响应特征的讨论,认为横向磁探头对套管上纵向裂缝长度的变化无判断能力,而纵向磁探头对横向裂缝长度变化的识别效果较弱.不同套管损伤的实验结果证实了数值模拟的正确性.

Three-dimensional finite element numerical simulation for time-domain electromagnetic casing inspection technology

A design scheme for non-contact casing detection equipment is presented.Finite element simulation technologies are used to calculate the time-domain electromagnetic responses of vertical and horizontal magnetic probes.The results show that the vortex generated by vertical magnetic probe is coaxial with the casing,while the vortex cased by horizontal magnetic probe is perpendicular to the former.The received signal of the magnetic probe is mainly come from the metal casing.And the response characteristics of the two magnetic probes are discussed separately under the conditions that there are hole,vertical crack and horizontal crack on the metal casing.The electromagnetic response simulation results for different diameter holes indicate that the two magnetic probes are all have high resolution for the hole-type damage.Results for the vertical and horizontal cracks with different parameters show that the horizontal magnetic probe has no ability to judge the changes of the vertical crack length.It is also found that the vertical magnetic probe has higher sensitivity to the changes of the horizontal crack width,but has weaker recognition effect to the changes of its length.The measurement results for different casing damages confirm the correctness of the numerical simulations.