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管道漏磁检测及其缺陷漏磁场的仿真技术研究具有十分重要的意义。在对各种漏磁场计算方法进行比较之后,选择了有限元法作为主要研究工具。叙述了漏磁检测的基本原理,介绍了漏磁管道检测装置的工作原理和基本结构,建立了管道漏磁检测中缺陷漏磁场计算的三维有限元模型,并以此为基础分别研究了缺陷漏磁信号特点、缺陷的几何尺寸与漏磁信号的关系、以及材料壁厚等对漏磁信号的影响等问题。通过对多磁化单元结构进行有限元模拟和试验仿真,发现多个磁化单元会造成磁场的叠加,磁化单元数量的增加会使缺陷处漏磁场增强,并且中间磁化单位的增加量要大于两侧。缺陷的几何尺寸影响漏磁场的分布,在一定缺陷直径范围内,缺陷深度与漏磁场信号强度呈近似线性关系。无论被测管道壁厚如何变化,相同几何参数的缺陷漏磁场轴向分量变化趋势仍然相同。适当选取提离值,将有助于获得良好的漏磁场信号。 相似文献
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有限元法在管道漏磁检测中的应用 总被引:12,自引:2,他引:10
介绍管道漏磁检测中有限元计算方法的基本原理,推导出轴对称的漏磁检测系统在极坐标下的有限元方程、网格剖分方法及有限元计算的边界条件,并计算出不同形状缺陷的管道的磁力线分布图.从计算结果可清楚地看出不同缺陷对磁力线分布造成的影响也不相同. 相似文献
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The effects of uniaxial stress on the normal (radial) component of the magnetic flux leakage (MFL) signal induced by blind-hole defects for depths of 25%, 50% and 75% of the thickness of the pipe wall were investigated with a pipe wall flux density of 1.24 T. These three defects were on the same surface as the magnetizer and sensor for the MFL signal (near side). A fourth 50% defect was on the pipe wall surface opposite the sensor (far side). Changes of as much as 47% in the MFL signal due to stresses of up to 300 MPa were observed. Increased changes in the stress dependent MFL signal were observed with increasing defect depth. Comparison of the near side and far side 50% defects indicated similar changes in the MFLpp signal as a function of stress, although the shape of the MFL signals was qualitatively different. The stress dependent MFL signal was also investigated for the near side 50% defect for pipe wall flux densities between 0.65 T and 1.24 T. A linear increase in the effects of stress on the MFL signal with increasing flux density was observed. Results demonstrated that the variation of the MFL signal with stress is primarily a bulk stress effect, although the effect of defect-induced stress concentrations upon the various MFL signals investigated could also be observed. 相似文献
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漏磁检测法已成功应用于各类铁磁性材料的检测中,但当代生产技术的革新和新应用领域的出现对漏磁检测法的检测速度提出了新的挑战。高速漏磁检测的信号出现畸变,制约着检测速度的进一步提高。对此,众多研究人员对信号畸变的机理进行研究,发现磁化滞后效应是影响高速漏磁检测信号的主要因素。当高速运动的钢管通过磁化线圈时,涡流使得管壁内的磁场无法达到稳定状态,从而影响了漏磁检测信号。在机理探究的基础上,提出了增大磁化线圈长度、采用多级磁化等方法来抑制高速漏磁检测时信号的畸变。动生涡流无损检测法和动生涡流热成像检测法等新电磁检测方法也被提出,并在高速检测时获得了较好的效果。 相似文献
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Magnetic flux leakage (MFL) is the most used technique for pipeline inspection, being applied through the use of instrumented PIGs. The pipe wall is magnetized and when metal loss or other irregularities occur, a larger fraction of the magnetic flux “leaks” outwards from the wall and is detected by sensors. MFL presents some limitations since it requires magnetic saturation of the pipe wall. Therefore, it is difficult to inspect small diameter and thick wall pipelines. Internal corrosion sensor (ICS) has been developed as a solution for internal corrosion measurements of thick walls. The technique, also called “field disturbance”, is based in a direct magnetic response from a small area of the wall. It is not necessary to achieve the magnetic saturation of the pipe material, and thus ICS performance is not affected by the thickness of the pipe wall. In the present work, finite element calculations are performed and the best resultant configuration of the sensor is proposed. Experimental tests with a prototype were carried out and the results give a strong indication of the validity of the theoretical model proposed for sizing. 相似文献
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提出一种油气管道裂纹漏磁场检测的数学分析方法。先根据麦克斯韦方程组推导出漏磁场数据分析模型。其次,利用三维有限元分析原理在Ansys环境下建立数学仿真模型。再将仿真结果与实际测试数据进行比较,确定该方法的可靠性。最后,通过仿真分析得出了裂纹几何参数(深度和宽度等)对漏磁信号特征的影响规律,并给出它们的关系曲线。该方法为实际利用漏磁场分布检测油气管道裂纹提供了重要的依据。 相似文献
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