在役缆索索力时空变换电磁检测原理与方法

Steel cables have been widely used in long-span prestressed structures like large Bridges, tourism cableways and so on, due to its outstanding advantages such as high strength, light weight. It is of great significance for the safety of the above structures to measure the in-service cable tension using appropriate methods. As a non-contact measurement method, electromagnetic method is not affected by the sag and boundary conditions of steel cables, so it has a potentially broad application. However, the problems of heating and hard to install also greatly restricted the application of this method. Based on the analysis of the current measurement technology, this project puts forward an electromagnetic testing principle for in-service cable tension measurement using the time-space transformation. The equivalence between the effect of spatial-domain magnetic field and time-domain magnetic field on steel cables is first studied, which transform the electromagnetic measurement of the cable tension from the time domain into the spatial domain. Therefore, this testing principle can break through the limitation on the existing electromagnetic measurement methods for cable tension which is caused by alternating current. Then, the project will take forward in-depth study on the principle from establishing magnetic characterization model for cable tension, studying on the static excitation method, probing into the method of magnetic field spatial filtering , seeking calibration method, researching the compensation method and so on. The results of this research project will rich the magnetic coupling mechanism in theory; and also search for a new principle for measuring the in-service cable tension, and provide a new method for the safety assessment of long-span prestressed structures.

钢缆索具有高强质轻等突出优点，广泛应用于桥梁、旅游索道等大型预应力结构。采用合适方法实现在役缆索索力检测对保证上述结构安全运营具有重要意义。电磁法作为一种非接触测量方法，其检测结果不受缆索垂度、边界条件等影响，具有广阔的应用前景。但也存在线圈发热、安装困难等不足，极大地制约该方法的应用。在此背景下，本项目在寻找空间域磁场和时间域磁场对缆索作用等效性的基础上，提出在役缆索索力时空变换电磁检测原理，将现有缆索索力电磁测量方法从时间域的测量转化为空间域的测量，突破已有电磁法测索力由于需要输入交变电流引入的测量方法上的限制。并从磁力表征模型、恒定励磁方法、磁场空间滤波方法、标定及补偿方法等方面对该检测原理进行深入研究。在理论上，该研究将丰富磁力耦合机理的相关内容；在实践上，将寻求得到一种全新的索力测量方法，从而为大型缆索结构安全评价提供新手段。

缆索作为一种深加工金属制品，广泛应用于斜拉桥、悬索桥、拱桥等桥梁中，作为一种关键承力部件，如何便捷地获取索力（即应力）状态对保证其安全使用具有重要意义。针对现有应力电磁方法多采用时变磁场作为激励磁场，存在线圈缠绕困难、长时激励线圈发热以及涡流影响检测结果的不足，本项目提出利用恒定磁场激励下，构件上产生的空间变化磁场实现应力检测，突破现有时变磁场方法的限制。.首先，提出了一种基于磁弹效应的应力恒磁检测原理，克服现有时变磁场应力检测中涡流效应对检测结果的影响，给出了一种均匀应力下铁磁构件起始磁化曲线恒磁推算方法。其次，确定了适用于缆索应力恒磁检测的永磁恒定磁场激励方法，使其满足局部均匀与全局衰减正交条件的空间变化磁场条件，实现了应力测量所需的磁场激励。然后，探寻了由缆索表面不同提离下磁感应强度外推外表面上磁感应强度的方法以及由构件外表面磁感应强度计算构件内部磁感应强度的方法，实现了由缆索外部测量值推知缆索内部磁场分布。进一步，研究了铁磁构件应力恒磁检测磁参数表征方法，在原理上确定了不同类型材料的微分磁导率同应力的关系方程，并最终确定了分别适用于高碳钢和中碳钢应力表征的磁参数。最后，在分析影响索力测量诸因素的基础上，设计缆索的退磁装置,削弱缆索剩磁对索力测量的影响，研制了缆索及其组成单元钢丝与钢绞线的检测传感器，开发了应力恒磁检测原型系统，实验结果表明应力检测误差小于10%。.本项目申请发明专利3项，授权1项，发表论文8篇，其中SCI收录5篇，获计算机软件著作权1项，培养博士研究生2名。项目成果为在役缆索索力检测提供了一种新途径，有望发展成为一种方便快捷的铁磁构件工作应力检测方法，同时也为获取铁磁构件起始磁化曲线提供了一种新思路，对推动铁磁材料电磁特性在役测量具有重要意义。.