磁层析成像管道检测信号空间传递过程的能量变化

Energy Change of Pipeline Signal Spatial Propagation Detected by Magnetic Tomography Method

磁层析成像管道检测方法已经被广泛应用于埋地和海底管道的无损外检测。该方法基于金属磁记忆原理,通过在管道外测量空间磁场分布中的异常情况来判别应力集中区的危险等级和位置。为了研究磁层析成像法管道检测信号在空间中的分布特征和传递规律,对磁化管道的应力集中区空间磁记忆信号的能量分布和变化规律进行了研究。利用磁偶极子场建立管道内壁应力集中区磁场模型,基于磁能理论对管道外不同提离空间磁记忆信号的磁场能量和磁能密度进行有限元计算,得出空间磁场的分布规律,分析了不同提离磁信号磁能密度之间的相关性。结果表明,管道外空气中的磁场能量随着提离值的增加而衰减,在管道外壁至提离值小于50 mm时衰减最快;管道外磁层析成像法检测的磁信号与管道内壁应力集中区信号同源。从理论上解释了磁层析成像管道检测的有效性,为从检测数据中提取有效信号提供了理论依据。

Magnetic tomography method has been widely used for nondestructive external inspection of buried and submarine pipelines,which is based on the principle of metal magnetic memory to discern the danger level and location of the stress concentration zone by measuring the anomalies in the spatial magnetic field distribution outside the pipeline.The distribution characteristics and spatial propagation law of pipeline inspection signal detected by magnetic tomography method,the energy distribution and change law of spatial magnetic memory signal in the stress concentration zone of magnetized pipelines are studied in this paper.The magnetic dipole field is used to establish the magnetic field model in the stress concentration zone of the inner wall of the pipeline,and the magnetic energy and energy density of spatial magnetic memory signals under different lift-off values outside the pipeline are finite element calculated based on the magnetic energy theory to derive the distribution law of spatial magnetic field and the correlation of magnetic energy density of magnetic signals under different lift-off value is analyzed.The results show that the spatial magnetic field energy outside the pipe decays with the increase of lift-off value,and the decay is the fastest within the distance of 50 mm from the outer wall of the pipe to the physical force;the correlation of magnetic energy density of different lift-off values shows that the magnetic signal detected by magnetic tomography method outside the pipe is homologous with the signal in the stress concentration zone of the inner wall of the pipe.Theoretically,it explains the effectiveness of magnetic tomography method and also provides evaluation indexes for extracting effective signals from the detection data.