连续油管分层缺陷磁导率扰动电磁检测方法与检测系统

板材的分层缺陷检测通常采用超声测厚法实现，但超声测厚法对近表层检测存在盲区，且高速检测系统复杂、成本高。本研究提出一种连续油管分层缺陷的磁导率扰动电磁检测新方法，并设计了相应的检测系统。该系统利用永磁体沿钢管或钢板的法向施加磁力，管板内分层产生内部磁场的畸变，进而引起局部区域的磁导率扰动，这一扰动沿厚度方向传递到表层，在空间上差动的涡流探头测量表层磁导率的相对变化，即可实现内部分层缺陷的检测与评估。从机理上阐明了分层缺陷的埋深对测点处相对磁导率变化的影响；随后，基于有限元模型研究了分层的长度、埋深、分层厚度等因素引起的测点处磁导率变化；最后，试验验证了理论分析和仿真结果的有效性。

Method and System of Magnetic Permeability Perturbation Detection for Delaminations in Coiled Tubing

Detection of delaminations in plates is usually realized by ultrasonic thickness measurement, but there are blind areas in near?urface layer, and the high?peed detection system is complex and costly. A new method of magnetic permeability perturbation electromagnetic detection of delaminations in coiled tubing is proposed, and a corresponding detection system is designed. Using a permanent magnet to apply magnetic force along the normal direction of the steel plate, the delamination within the plate produces internal magnetic field distortion, which in turn causes magnetic permeability perturbation in the local area. The perturbation is transmitted to the surface along the thickness direction. The detection and evaluation of internal delaminations can be achieved by measuring the relative change of magnetic permeability on the surface layer with a differential eddy current probe. The effect of the burial depth of the delamination on the relative permeability change at the measurement point is mechanically elucidated; subsequently, the magnetic permeability change at the measurement point due to the length, burial depth, and thickness of the delamination is investigated based on the finite element model; finally, the validity of the theoretical analysis and simulation results is experimentally verified.