建筑钢结构隐性损伤与磁记忆信号的量化关系

Hidden damage of building steel structure is one of the sources of hidden danger and may cause structural catastrophe. Steel structure building belongs to the ferromagnetic materials. The natural earth magnetic field is sensitive to the hidden damage change and has metal magnetic memory effective. Accordingly, this project aims to research the quantifiable relationship between the magnetic memory signals and the hidden damage of steel structure building. By theoretical analysis, experimental study, numerical simulation and engineering field measurement and other means, according to the cross connection theory of steel structure building and the ferromagnetism, those difficult problem will be solved, followed as that how to acquisitive and processing magnetic memory signal, how to extract the characteristics of magnetic memory signals and how to collect and treat the weak magnetic field information caused by the hidden damage change of steel structure building. The mechanism of hidden damage and magnetic memory signal changes will be analyzed, magnetic memory signal-damage theory related model for steel structure building will be established, and the quantifiable constitutive relation between the magnetic memory signal and hidden damage of steel structure building will be gotten. This constitutive relation can directly determine the site and the size of the hidden damage. On this basis, a quantitative evaluation method will be established based on the magnetic memory signal change according to hidden damage state of steel structure building, this methods will be able to early find the hidden damage and detect damage degree of steel structure building. The special point of this project are where the hidden damage will be early found and how much the hidden damage will be determined by magnetic feature, research achievement will provide a new way for nondestructive testing of steel structure building.

建筑钢结构的隐性损伤，是安全隐患的祸端之一，会引起结构灾变。建筑钢结构属于铁磁材料，其内部隐性损伤对天然地磁场作用具有敏感的记忆效应。据此，本项目旨在确定建筑钢结构隐性损伤与其对应的磁记忆信号的量化关系。采用理论分析、试验研究、数值模拟和现场实测等手段，在建筑钢结构和铁磁学交叉理论基础上，研究具有杆系、薄壁特点的建筑钢结构微弱磁记忆信号采集和处理方法，提取磁记忆特征信号，解决建筑钢结构磁记忆弱磁场信息采集与处理难的问题；分析隐性损伤与磁记忆信号变化的内在联系规律，建立建筑钢结构磁记忆信号-损伤理论关系模型，得到隐性损伤与磁记忆信号之间的量化本构关系，能够直接确定隐性损伤的大小。在此基础上，建立建筑钢结构隐性损伤磁记忆检测的量化评判方法，可以提早发现建筑钢结构的隐性损伤并评判其潜在危害程度。本项目具有用"磁"来确定"隐性损伤"发生部位与大小的特点，研究成果将为建筑钢结构的无损检测提供新途径。

建筑钢结构正常使用过程中，将不可避免地产生一些早期损伤。随着损伤积累，抗力不断衰减，从而威胁整个结构的安全。尽早发现结构的应力集中和损伤区域，对保证结构安全和防止重大事故发生具有重要意义。本项目基于磁记忆检测技术，在建筑钢结构和铁磁学交叉理论基础上，从理论分析、数值模拟、试验研究三方面开展了研究，取得的主要成果如下：1、机理研究：基于Jiles-Atherton模型，通过理论推导，证明应力致磁场过程不仅与应力有关，还与初始磁化状态有关；在原模型中加入具有应力相关性的应力退磁项和有效磁畴耦合系数，修正后模型能很好的解释拉压磁化的非对称性现象；提出了塑性变形下的Jiles-Atherton模型，数值模拟表明在塑性变形和残余变形初期，非滞后磁化强度和磁化强度均急剧下降，且非滞后磁化强度和磁化强度均对残余应变更敏感，下降趋势更为剧烈，当塑性应变和残余应变继续增大时，非滞后磁化强度和磁化强度缓慢下降，逐渐趋于平缓。2、模拟研究：利用ANSYS软件进行力磁耦合分析，考虑应力对铁磁材料磁导率的影响，对拉伸试验进行有限元模拟，分析了不同拉应力状态下试件表面漏磁场分布情况，并研究了各影响因素（提离值、缺陷宽度、缺陷深度等）对漏磁信号的影响，结果表明，磁记忆信号尽管在幅值大小上有些误差，但模拟结果和试验结果数据基本吻合，具有一致的变化规律，法向分量和切向分量均随提离值高度的增加而减小，随缺陷宽度的增加而增加，随缺陷深度无明显变化；3、试验研究：开展了光滑无缺陷和含浅槽缺陷钢板件、焊接钢板件、工字钢梁静载和疲劳、门式刚架水平低周往复荷载，以及钢丝绳、钢框架等试验研究。分析了各试件在不同载荷下，磁记忆信号法向分量Hp(y)和梯度K值的变化规律，并针对不同试验提取相应的磁信号特征参数。结果表明，不同试件在受到载荷后，磁信号曲线均表现出很强的规律性；通过合理提取磁信号特征参量可准确预测试件的受力状态，确定应力集中区，得到试件损伤程度与磁信号的量化关系。该项目研究成果是磁记忆检测技术用于建筑钢结构领域的重要理论和应用基础。