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Studies on Identification of Mechanical Loading Applied to Composite Plates Using Distributed Fiber Optic Sensors

使用分布式光纤传感器识别复合板机械载荷的研究

基本信息

批准号：
07455391
负责人：
TAKEDA Nobuo
金额：
$ 4.67万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455391/
关键词：
Fiber Optic Sensor Distributed Sensor Mechanical Load Identification Composite Materials Smart Structures Smart Materials Crack Detection Modal Domain スマート材料力学負荷偏波維持スマート構造

项目摘要

The purpose of the present study is to develop a fundamental theory of mode couplings in modal-domain polarization-maintaining optical fibers subjected to an arbitrary three-dimensional stress state, and to demonstrate its validity through comparison with some experiments for possible applications to smart materials/structures.Mode couplings in polarization-maintaining optical fibers embedded in materials under different loading conditions were theoretically derived to demonstrate the effects of embedded material properties as well as types of loadings such as axial tension, pure bending, torsion and transverse compression. Practically useful formulas were derived for mode coupling equations by expanding the stresses into Taylor series around the center of the optical fiber.Considering a sensitive response of mode couplings under transverse compressive loadings, load sensor modules were developed. For stable and quantitative measurements, the following design criteria were establishied : (1)to protect the optical fiber without coatings, (2)to attach a sensor head, (3)to load the optical fiber normal to the fiber axis, (4)to fix the angle between fiber principal and loading directions to 45 degree, and(5)to fix the loading length to 1 mm. Different types of load sensor modules were designed and fabricated for performance tests, and practical miniature load sensor modules were successfully developed.In addition, some attempts were made to detect stress concentrations due to cracks or notches. Different sensitivities between sensor outputs and crack lengths were noticed under Mode I and Mode II loadings. The sensitivity were found to be extremely high when the beat length of fundamental modes of the optical fiber was equivalent to the crack length. However, the sensitivity became low when the crack length is less than 5% of the beat length of fundamental modes of the optical fiber.

本研究的目的是建立模域保偏光纤在任意三维应力状态下模式耦合的基本理论，并通过与一些可能应用于智能材料/结构的实验的比较来证明其有效性。从理论上推导了不同载荷条件下保偏光纤嵌入材料中的模式耦合，证明了嵌入材料特性以及轴向拉伸、纯弯曲、扭转和横向压缩等载荷类型对保偏光纤的影响。通过将光纤中心周围的应力展开成泰勒级数，推导出了实用的模式耦合方程公式。考虑到模态耦合在横向压缩载荷下的敏感响应，开发了载荷传感器模块。为了稳定和定量的测量，建立了以下设计准则：(1)保护无涂层的光纤，(2)附加传感器头，(3)使光纤与光纤轴垂直加载，(4)将光纤主体与加载方向的夹角固定为45度，(5)将加载长度固定为1mm。设计并制作了不同类型的负载传感器模块进行性能测试，成功开发出实用的微型负载传感器模块。此外，还进行了一些尝试，以检测由于裂纹或缺口引起的应力集中。在I型和II型加载下，传感器输出和裂纹长度之间的灵敏度存在差异。当光纤基模的拍长与裂纹长度相等时，灵敏度极高。但当裂纹长度小于光纤基模拍长的5%时，灵敏度变低。