管线钢磁力耦合效应及在线无损应力检测

Magnetic Coupling Effect and On-line Nondestructive Stress Detection of Pipeline Steel

天然气管道服役期内的载荷变异、介质侵蚀、环境变化等诱发的集中应力使管道强度接近甚至超过设计值,形成安全隐患,而现有的检测手段很难实现在线无损应力检测。结合铁磁材料磁力学机理,开展了X80管线钢的磁力耦合效应微观特性试验研究,探讨了应力引起磁畴结构变化的机理。以X80管线钢圆棒试样为研究对象,设计了基于磁力耦合效应的在线无损应力检测装置,提出了X80管线钢磁力耦合效应应力检测的理论基础及应用方法,并对试验数据进行了分析。结果表明:①在单向拉/压应力作用下,管线钢试样应力变化诱发磁畴结构的改变,从而使受拉方向上的磁化强度增大,使受压方向的磁化强度减小;②恒定加载速率下,在弹性变形阶段,X80管线钢圆棒试样的拉/压应力与通过其截面的感应磁通量之间基本呈现线性关系;③试验得出的X80管线钢试样各种工况的感应磁通量-应力关系吻合较好,精度能满足工程要求。基于管线钢的磁力耦合效应,以感应磁通量为参量建立的磁力本构模型能准确地反映服役管道应力变化,为在线无损应力检测提供了新方法。

During service of natural gas pipeline,the concentrated stress induced by load variation,medium erosion and environmental change makes pipeline strength close to or even exceed the design value,thus forming a potential safety hazard.However,it is difficult to realize on-line non-destructive stress detection by existing detection methods.Based on the magnetism-stress mechanism of ferromagnetic materials,the experimental study on the micro-characteristics of magnetism-stress coupling effect of X80 pipeline steel was carried out,and the mechanism of domain structure change caused by stress was discussed.An on-line non-destructive stress detection device based on magnetic coupling effect was designed for X80 pipeline steel rod samples.The theoretical basis and application method of stress detection of X80 pipeline steel based on magnetic coupling effect were put forward,and the test data were analyzed.The results show that,(1) under unidirectional tension/compression stress,the stress change of pipeline steel specimen induces the change of domain structure,which increases the magnetization intensity in the direction of tension and decreases the magnetization intensity in the direction of compression.(2) At constant loading rate,the tension/compression stress of X80 pipeline steel bars is linearly related to the induced magnetic flux through its cross section during the elastic deformation stage.(3) The inductive flux--stress relationships of X80 pipeline steel samples under various working conditions are in good agreement,and the accuracy can meet the engineering requirements.The magnetic constitutive model,which is based on the magnetism-stress coupling effect of pipeline steel and takes the induced magnetic flux as a parameter,can accurately reflect the stress change of pipeline in service,and provides a new method for on-line non-destructive stress detection of in-service pipeline.