X80管线钢矫顽力与应力关系

Relationship between coercivity and stress of X80 pipeline steel

长输油气管道沿途运行环境复杂,期间异常外载荷易导致局部区域应力集中,增加管道运行风险。基于矫顽力的应力测量方法是评价管道安全裕度、预防管道安全事故的新兴技术。通过深入探究铁磁性材料原子磁矩、磁畴结构、磁滞回线等磁特性,阐明了矫顽力测量应力的力磁耦合机理,介绍了现有的单向应力状态下矫顽力-应力关系表达式,推导了双向应力状态下矫顽力-应力关系模型,并开展实验对X80管线钢单、双向应力状态下的矫顽力-应力关系进行验证。实验结果表明,X80管线钢在单向应力状态下的矫顽力与应力间呈现良好的线性关系,双向应力状态下矫顽力与两向应力均相关,且规律与推导模型相符。研究成果为矫顽力法的现场应用提供了理论和实验依据,证明矫顽力法能够准确测量X80管线钢应力水平,是评估在役管道安全裕度的可靠方法。

The operation environment along the long-distance oil and gas pipelines is complex, and the abnormal external load during pipeline operation may lead to local stress concentration, which will increase the operation risk of pipeline.The coercivity-based stress measurement method is a new technology to evaluate the safety margin and prevent the safety accidents of pipeline. Herein, the magnetic properties of ferromagnetic materials, such as atomic magnetic moment, domain structure and hysteresis loop, were explored in depth. The mechanism of mechanical and magnetic coupling in coercivitybased stress measurement was clarified. The existing expressions of relationship between coercivity and stress in uniaxial stress state were introduced. The model of relationship between coercivity and stress in biaxial stress state was deduced.Besides, experiments were performed to verify the relationship between coercivity and stress of X80 pipeline steel in the uniaxial and biaxial stress states. The experimental results show that there is a good linear relationship between the coercivity and stress of X80 pipeline steel in uniaxial stress state, the coercivity is related to the biaxial stress in the biaxial stress state, and the laws are consistent with the models derived herein. The research result provides a theoretical and experimental basis for the field application of coercivity-based stress measurement method, which is proved to be capable of accurately measuring the stress of X80 pipeline steel, and it is a reliable method to evaluate the safety margin of in-service pipeline.