高速漏磁检测过程中管道内外壁缺陷定位方法研究

管道内外壁缺陷的有效区分是对缺陷进行有效量化的前提，提出一种基于动生涡流的高速漏磁检测过程中管道内外壁缺陷的定位区分方法，利用涡流磁场与外磁场的耦合作用时内外壁磁场信号的变化差异特征区分缺陷位置。首先建立高速漏磁检测数学模型，分析了涡流分布特点以及涡流磁场与外磁场耦合作用规律，利用有限元方法计算分析不同位置时，耦合作用规律对管道内外壁磁化状态影响及内外壁缺陷漏磁场信号差异特征；设计高速漏磁检测实验平台，对不同运行速度、不同检测位置处钢管内外壁缺陷区分效果进行实验研究。结果表明，接近磁化线圈位置时，管壁内产生的涡流磁场方向与管道外壁磁场方向相同、与管道内壁磁场方向相反，在离开磁化线圈位置时，涡流磁场方向与管道外壁磁场方向相反、与管道内壁磁场方向相同；不同检测位置处，管壁磁场变化规律相反，且速度越快，磁化状态影响受影响程度越大，内外壁漏磁场信号差异特征越明显，高速检测时可有效对管道内外壁缺陷进行定位区分，实验结果和理论分析具有很好的一致性。

Study on the defect location method of inner and outer wall of pipeline during high-speed magnetic flux leakage testing

The effective differentiation of pipe inner and outer wall defects is the premise of effective quantification of defects. A method of locating and distinguishing pipe inner and outer wall defects in high-speed magnetic flux leakage detection based on dynamic eddy current is proposed. In this method, the defect location is distinguished by the variation characteristics of magnetic field signals in inner and outer walls when the eddy current magnetic field and external magnetic field are coupled. Firstly, the mathematical model of highspeed magnetic flux leakage detection is established, and the eddy current distribution characteristics and the coupling law of eddy current magnetic field and external magnetic field are analyzed. By using the method of finite element analysis, the influence of coupling action law on the magnetization state of the inner and outer wall and the different characteristics of magnetic leakage signal of inner and outer wall defects at different positions are calculated. A high-speed magnetic flux leakage test platform is designed, and the effect of defect discrimination on the inner and outer wall of steel pipe at different running speeds and detection positions is studied experimentally. Results show that when the pipe enters the position of magnetized coil, the direction of the eddy current magnetic field is the same as that of the outer wall of the pipe. But it is opposite to that of the inner wall of the pipe. When the pipe leaves the position of the magnetized coil, the direction of the eddy current magnetic field is the same as that of the inner wall of the pipe, but opposite to that of the outer wall of the pipe. At different detection positions, the variation law of pipe wall magnetic field is obviously opposite, and with the increase of detection speed, the magnetization state is affected more obviously, and the more obvious the difference of magnetic leakage signals between inner and outer walls. High-speed detection can effectively locate and distinguish the defects of the inner andouter wall of the pipe. The experiment results and theoretical analysis have very good consistency