Magneto-Elastic Sensors for Postearthquake Damage Detection in Steel Structures

9724948王在这个项目中，研究开发了一种基于铁磁结构材料磁化特性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设计了许多成功的磁弹性传感器。这些传感器大多是圆柱形的，主要用于测量圆柱形试件中的力和应力。这有时被认为是一个严重的缺陷，因为典型结构中的绝大多数结构元素都是平面的(梁、梁、板和甲板)，正在研究的样品不能被封闭在传感器中。利用磁阻测量的概念进行应力分析，实现了一种新颖的平面传感器设计。传感器的设计理念强调在结构的屈服后区域进行应力测量的能力。这项研究包括以下任务：1)设计能够在产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)开发与圆柱形设计不同的表面贴装平面传感器设计，以及4)开发合适的本构模型来确定用于传感器设计和校准的渗透率-应力关系。该传感器具有很强的灵活性，可用于各种结构监测方案、平面内和圆形截面的测力、桥梁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. ***