基于磁记忆的油气管道应力损伤检测方法研究

Study on the testing method of oil-gas pipeline stress damage based on magnetic memory

应力集中是油气管道损坏的关键因素,对管道安全构成重大威胁。对其进行有效检测,既可发现由应力集中引起的机械损伤亦可实现对管道早期损伤的预判。磁记忆检测技术作为一种应力检测方法得到了业界认可。从能量平衡角度出发,分别从宏观和微观的角度对应力作用下的铁磁体磁记忆信号特征进行分析,建立应力与材料磁化率及原子磁矩之间的理论关系模型。采用基于第一性原理的CASTEP软件对铁碳金属体系的磁记忆力磁耦合过程进行仿真。结果表明,铁磁体在外力作用下,体系能量将重新平衡并达到稳定状态,电子能带及态密度分布特征发生改变,导致材料磁性下降,原子磁矩及材料磁化率随应力增大呈线性减小的变化趋势。通过对含裂纹管道的磁记忆检测,验证了应力损伤磁记忆检测方法的理论分析正确性及工程应用有效性。

Stress concentration is the key factor that induces the damage of oil-gas pipeline. It is a serious threat to the safe of pipeline. Effective test can both find the mechanical damage induced by stress concentration and achieve pre-judgment of early damage of pipeline. Magnetic memory technology has been widely recognized by the customers as a method of stress testing. In this paper, magnetic memory signal character of ferromagnetic material in different stress application is analyzed in the macroscopic and microcosmic range from the point of energy balance. The theory relation model between stress and susceptibility or atomic magnetic moment is build. Force magnetic coupling process of magnetic memory in Fe-C metal system is simulated by CASTEP software, which is based on first principle. The results show that ferromagnetic system energy balances and achieves to stable state when the stress is applied. It also weakens the material magnetism and changes the distribution character of electron band structure and density of state. Atomic magnetic moment and susceptibility decrease linearly along with the increase of stress. Finally, magnetic memory testing experiments on pipeline contained crack demonstrate the correctness of theory analysis and effectiveness of engineering application.