Magneto-Elastic Sensors for Postearthquake Damage Detection in Steel Structures

在本项目中，研究开发一种基于铁磁性结构材料磁化特性测量的直接应力测量方法。研究表明，铁磁材料的磁化特性与应力水平有关，世界各地的研究人员已经设计出了许多成功的磁弹性传感器。这些传感器大多为圆柱形设计，主要用于测量圆柱形试样中的力和应力。这有时被视为一个严重的缺陷，因为典型结构中的绝大多数结构元素是平面的（梁和梁，板和甲板），并且所调查的样品不能被封闭在传感器内。利用磁阻测量应力分析的概念，设计一种新颖的平面传感器。传感器的设计理念强调在结构屈服后区域进行应力测量的能力。研究包括以下任务：1)设计可在屈服后区域工作的传感器；2)开发能够检测屈服的残余应力传感器；3)开发与圆柱形设计相比可安装在表面的平面传感器设计；4)开发用于确定渗透-应力关系的合适本构模型，用于传感器设计和校准。该传感器具有灵活性，可用于多种结构监测方案、平面和圆形截面的力测量、桥梁梁的预应力损失监测以及结构构件的震后评估。＊＊＊

9724948 Wang In this project, research is conducted toward development of a method of direct stress measurement based on the measurement of magnetization characteristics of ferro-magnetic structural materials. It has been shown that the magnetization characteristics of ferro-magnetic materials are related to the stress level, and a number of successful magneto-elastic sensors have been designed by researchers around the world. Most of these sensors are cylindrical in design and are primarily designed for measuring force and stress in cylindrical specimens. This is sometimes seen as a severe deficiency, since the bast majority of structural elements in a typical structure are planar (girders and beams, plates and decks) and the specimen under investigation cannot be enclosed within the sensor. A novel planar sensor design will be achieved using the concept of magnetic reluctance measurement for stress analysis. The sensor design philosophy emphasizes the ability to make stress measurements in the post yield region of the structure. The research consists of the following tasks: 1) design of sensors that can operate in the postyeild zone, 2) development of a residual stress sensor capable of detecting yielding, 3) development of a surface mountable planar sensor design in contrast to a cylindrical design, and 4) development of a suitable constitutive model for determination of permeability-stress relationships for sensor design and calibration. The proposed sensor is flexible and can be utilized for a variety of structural monitoring schemes, force measurement of inplanar and circular cross-sections, monitoring of prestress loss in bridge girders, and postearthquake evaluation of structural members. ***