基于矫顽力的管道应力检测系统研究

发布时间：2018-04-01 15:32

本文选题：铁磁性材料　切入点：矫顽力　出处：《沈阳工业大学》2017年硕士论文

【摘要】：随着我国油气管道的大规模运用,管道网络的运行安全问题更加的值得关注。目前在役油气管道通常选用低碳钢等铁磁性材料制作,管道在长期实际工程运行时可不避免会产生应力集中区域,应力集中区域的存在会导致破裂及腐蚀等管道缺陷,产生不良后果并造成巨大经济损失和生命财产安全。对在役管道重要防护区域定期检测,是减少应力导致安全事故的重要手段。应力会对磁性材料的特性参数造成一定的影响变化,而应力与材料矫顽力间的关系相对简单易于检测,利用矫顽力数值对管道所受应力进行评估,对管道应力检测具有重要意义。本文对应力对铁磁性材料矫顽力的影响进行了深入的分析;应力的施加会对磁化过程中不可逆磁化阶段形成了阻碍,而矫顽力的形成与这一阶段有直接关系,因此应力施加会对铁磁性材料产生影响。提出了一种基于矫顽力的管道应力检测技术,构建了基于矫顽力的管道应力检测硬件和软件系统。该系统采用U型探头进行检测,探头置于被测工件表面,利用低频正弦信号经过功率放大电路接入激励线圈将U型探头与被测工件进行交流磁化,感应信号通过感应信号调理电路进行处理产生感应信号。主控芯片接到脉冲信号后将此刻激励端电流数值通过矫顽力采集电路进行采集,经过计算得到材料的矫顽力数值。通过矫顽力数值的分析可以间接得到材料受到应力大小,从而进行应力评估。实验中,选取不同频率对U型传感器的感应信号进行分析,确定磁化最佳频率,并进行了系统装置的准确性及稳定性实验,选用Q235钢材作为工件材料在弹性形变阶段进行在线拉力实验,证明应力与矫顽力存在线性关系,后依次选择管道所用的X70管道低碳、X80管道低碳钢作为材料工件进行在弹性形变阶段的拉力实验,对不同厚度的不受应力的Q235钢材工件进行矫顽力测量。实验结果表明:U型探头在30Hz-50Hz频率下磁化效果最佳,基于矫顽力的应力检测系统检测Q235等材料在6mm厚度范围内的系统误差范围为±2%;测量精度为0.1A/m;标准差为1.92。铁磁性材料所受到的应力与测量得到的矫顽力数值呈现线性关系,不同管道材料对矫顽力与应力的变化率有一定影响,但不影响应力与矫顽力线性关系。在12mm内同一材料不同厚度不会对系统装置检测的矫顽力数值造成影响。
[Abstract]:With the large-scale use of oil and gas pipelines in China, the safety of pipeline network operation is more worthy of attention. At present, in service oil and gas pipelines are usually made of low carbon steel and other ferromagnetic materials. In the long run of actual engineering, the stress concentration area can not be avoided, and the existence of stress concentration area will lead to pipeline defects, such as rupture and corrosion, etc. Causing adverse consequences and causing huge economic losses and safety of life and property. Regular inspection of important protected areas of existing pipelines, Stress can influence the characteristic parameters of magnetic material, and the relationship between stress and coercivity is relatively simple and easy to detect. In this paper, the effect of stress on coercivity of ferromagnetic materials is analyzed. The application of stress will hinder the irreversible magnetization stage in the process of magnetization, and the formation of coercivity is directly related to this stage. Therefore, stress exertion will have an effect on ferromagnetic material. A coercivity based pipeline stress detection technique is proposed, and a hardware and software system of pipeline stress detection based on coercivity is constructed. The system uses U-shaped probe to detect the stress. The probe is placed on the surface of the workpiece being tested, and the U-shaped probe and the workpiece are magnetized AC by using the low frequency sinusoidal signal through the power amplifier circuit to connect the exciting coil. The inductive signal is processed by the induction signal conditioning circuit to produce the inductive signal. After the main control chip receives the pulse signal, the current value of the exciting end is collected through the coercivity acquisition circuit. The coercivity value of the material can be calculated by the analysis of the coercivity value. The stress magnitude of the material can be indirectly obtained by the analysis of the coercivity value, and the stress can be evaluated. In the experiment, the inductive signals of the U-shaped sensor are analyzed with different frequencies. The optimum frequency of magnetization is determined, and the accuracy and stability of the system are tested. The on-line tension test of Q235 steel as workpiece material in elastic deformation stage proves that there is a linear relationship between stress and coercivity. The X70 low carbon steel used in the X70 pipeline was selected as the material workpiece to carry out the tensile test at the elastic deformation stage. The coercivity measurement of different thickness unstressed Q235 steel workpieces is carried out. The experimental results show that the #number0# U probe has the best magnetization effect at 30Hz-50Hz frequency. The stress detection system based on coercivity has a linear relationship between the stress of ferromagnetic materials and the measured coercivity. The systematic error range of Q235 and other materials in the 6mm thickness range is 卤2, the measuring accuracy is 0.1 A / m, and the standard deviation is 1.92. The change rate of coercivity and stress is influenced by different pipe materials, but the linear relationship between stress and coercivity is not affected. Different thickness of the same material in 12mm will not affect the coercivity value measured by the system device.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE973.6

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