基于光纤光栅传感器的玻璃纤维复合材料层间应变测试的实验分析

通过对内埋未封装光纤光栅传感器(Fiber Bragg Grating,FBG)的玻璃纤维增强复合材料进行力学实验分析,得到不同试件层间的应变曲线与试件断面的微观截面图.探讨了玻璃纤维复合材料固化过程中温度和压力对FBG传感器的传感性能的影响,深入分析了FBG传感器与玻璃纤维复合材料的融合度以及弯曲实验中FBG传感器检测精度.在试件三点弯曲实验中,与传统电测方法不同,应用新型未封装FBG传感器进行复合材料的层间应变测量,得到的层间应变与载荷数据,拟合直线的线性相关系数均在0.99以上,并且传感器在监测不同试件同一层的层间应变的相对误差不超过5％.为应用FBG传感器检测实际的复合材料构件内部应变以及形成FBG传感网络损伤监测系统提供了实验基础.     

光纤光栅传感器对钢筋混凝土内部应变的测量及温度效应的研究

本文应用光纤光栅传感器实现了对钢筋混凝土试件内部应变的测量．试验不仅就应用光纤光栅进行混凝土结构内部应变测量的技术、工艺进行研究，还通过设计温度控制试验，考察了光纤光栅传感器的温度补偿问题，以及横向应变对测量结果的影响．     

基于双光纤光栅的冰压力传感器研究

冰压力是高纬度地区结构的重要荷载,然而传统的基于电阻应变计开发的冰压力传感装置在稳定性与耐久性上遇到难以跨越的难题。光纤光栅是目前在智能材料系统与结构健康监测研究与应用最为广泛的敏感材料之一,具有分布式绝对测量、抗腐蚀能力强等优点。本文基于双光纤光栅应变测量原理,考虑冰压力测试装置的环境条件,设计开发出冰压力传感装置,详细推导和试验验证了该装置的传感特性,并将试验与理论结果进行了对比。研究结果表明该装置具有温度自补偿、测量值与荷载作用点无关、线性度和重复性好、精度较高等优点,具有良好的应用前景。     

基于准分布式FBG传感器的均质材料内部应变测试的试验研究

采用环氧树脂材料作为试验载体,使用没有任何保护性封装的、运用波分复用技术在同一光纤上刻入三个布拉格光栅的基础FBG传感器,来监测液体树脂流动及固化成型的全过程,并使用固化成型的环氧树脂板进行三点弯曲试验。将所得数据与有限元模拟数值解进行比较,来验证在去除封装、将传感器自身应变影响降到最低的情况下,FBG传感网络是否依然能够有效地反映出试验对象在各种情况下的内部应变。本文给出了FBG光纤光栅在逐级静力荷载加载下材料内部三点弯曲的应变图,并通过数值计算分析了未封装光纤在复合材料内部受力过程中的力学性能。     

光纤光栅传感器应用于典型复合材料梁内部应变测试的试验研究

利用埋设在复合材料内部的未封装光纤光栅(Fiber Bragg Grating,FBG)传感器监测环氧树脂梁和玻璃纤维层压梁在三点弯曲过程中的应变变化,并与理论值进行对比,结果表明:两者所得的应变变化趋势吻合良好.光纤光栅传感器测量典型复合材料梁内部应变的方法不仅适用于各向同性的环氧树脂复合材料,而且适用于各向异性的玻璃纤维复合材料.     

基于光纤光栅的直升机桨叶应变试飞研究

研制了基于光纤布拉格光栅(FBG)传感原理的光纤光栅应变机载测试系统,并应用于直升机旋翼桨叶的外场试飞测试,使直升机桨叶应变试飞实现了光学传感。首先基于等强度梁开展电学应变计与FBG应变计的对比测试,验证了两者测量应变的一致性;其次搭建桨叶运动姿态物理仿真平台,并开展基于模拟桨叶的FBG挥舞弯曲应变测试,初步验证了FBG应用于桨叶应变测试的可行性;最后在直升机飞行试验中,使用FBG网络动态测量桨叶多剖面的分布式挥舞弯曲应变,并分析和对比电学应变计与FBG传感器阵列的实测数据,验证了分布式FBG网络应用于直升机桨叶试飞的技术可行性。     

可控薄弱环节复合材料圆柱壳的耐撞性研究

为了验证SMA可控薄弱环节的效果,制作了含有与不含有SMA丝的玻璃/环氧复合材料圆柱壳试验件,并对其进行了准静态轴向压缩试验,比较了各种试件的峰值载荷、平均载荷以及吸能能力。试验结果表明,可控薄弱环节不但可以降低试件的峰值载荷,而且能够改善复合材料结构的耐撞性能,有望解决传统复合材料吸能结构设计中静强度(刚度)与耐撞性之间的矛盾问题。     

基于CT扫描的花岗岩三维数值试件重构模型及应用

本文以花岗岩试件为研究对象,借助于先进的CT技术获取试件内部结构切片图像,利用数字图像处理技术实现了基于CT图像的花岗岩试件结构的识别和表征,基于矢量化方法和岩石破裂过程分析系统RFPA3D建立了花岗岩三维数值试件,对花岗岩试件单轴压缩破裂过程进行了数值模拟。通过数值试验结果与物理实验结果对比发现,基于CT扫描的花岗岩数值试件的破裂模式与室内实验得到的破裂模式相似,为深入研究岩石、复合材料等力学特征提供了一种可行方法。     

混凝土内部应变光纤测量结果及分析

本文采用迈克尔逊（Michelson)光纤白光应变测量干涉系统,利用新型光纤传感探头,对混凝土内部的一维和二维应变状态进行了测量,给出了混凝土试件单轴和两轴的力学实验结果并与Instron8505液压伺服材料实验机得到的结果进行了比较和分析。     

Hopkinson拉杆试验的优化与高导无氧铜拉伸本构关系的确定

为有效测量试件中的应力、应变及应变率,Hopkinson拉伸试验(TSHB)必须作优化分析,所进行的数值模拟涉及试件与杆件等连接对于实验结果的影响.为减小上升前沿、惯性效应且使试件处于一维应力及均匀应力与应变状态,优化的试件具有一定的长度与形状要求.对于高导无氧铜,由准静态试验及不同应变率与温度的优化TSHB试验得到一...     

Monitoring damage in holed CFRP laminates using embedded chirped FBG sensors

This study proposes a new approach to monitoring the damage process in holed CFRP laminates using an embedded chirped fiber Bragg grating (FBG) sensor. To this end, we experimentally and numerically investigated the damage process and the damage-induced changes in the spectrum shape. It was experimentally confirmed that multiple types of damage (e.g., splits, transverse cracks and delamination) appeared near a hole, and that the spectrum shape of the embedded chirped FBG sensor changed as the damage extended. Our proposed simulation for the reflection spectrum considering the damage agreed with the experiments. Furthermore, this study investigated the effect of each damage pattern on the changes in the spectrum shape. Finally, based on these discussions, we present simple damage identifications with the embedded chirped FBG for the holed CFRP laminates under completely unloaded conditions.     

埋光纤光栅传感器智能土木结构应变监测

采取与土木工程施工特点相适应的操作工艺与保护方法，将光纤Bragg光栅传感器埋入钢筋混凝土结构中，分别在实验室和实际工程施工现场对混凝土内部的应变进行了测量。实验中光纤Bragg光栅传感性能良好，能够监测混凝土内部应变状态，显示出成活率高、绝对值测量、寿命长等优势，为建立基于光纤传感器的结构健康监测系统奠定了基础。     

Development of an Optical System for Simultaneous Ultrasonic Wave Propagation Imaging at Multi-points

This paper introduces the development of an optical system for simultaneous ultrasonic propagation imaging at multi-points. For the system, fiber acoustic wave grating sensors (FAWGSs) and a Q-switched pulsed laser (QPL) mirror scanner are utilized for simultaneous multipoint sensing and remote scanning ultrasonic generation, respectively. The structural strain-free FAWGS based on a fiber Bragg grating allows simultaneous multipoint acoustic emission (AE) sensing. A structure in which the FAWGSs are deployed can sense external ultrasonic stimulus. Consequently, the structure with the integrated FAWGSs cannot only detect damage event under the passive AE technique, but can also evaluate the damage under the active scheme of ultrasonic transmission and reception. The feasibility of the simultaneous multipoint ultrasonic sensing system based on the FAWGSs as built-in sensors is studied with ultrasound transmitted by a piezoelectric transducer and a QPL. Then the QPL ultrasonic generator is modified into a QPL mirror scanner for laser beam scanning and finally an optical UPI system is integrated. The ultrasonic wave propagation movie (UWPM) obtained by the optical UPI system visualizes impact damage on a carbon-fiber reinforced composite.     

Simultaneous Measurement of Effective Chemical Shrinkage and Modulus Evolutions During Polymerization

A novel method is proposed to simultaneously measure the effective chemical shrinkage and modulus evolutions of advanced polymers during polymerization. The method utilizes glass fiber Bragg grating (FBG) sensors. They are embedded in two uncured cylindrical polymer specimens with different configurations and the Bragg wavelength (BW) shifts are continuously documented during the polymerization process. A theoretical relationship is derived between the BW shifts and the evolution properties, and an inverse numerical procedure to determine the properties from the BW shifts is established. Extensive numerical analyses are conducted to provide general guidelines for selecting an optimum combination of the two specimen configurations. The method is implemented for a high-temperature curing thermosetting polymer. Validity of the proposed method is corroborated by two independent verification experiments: a self-consistency test to verify the measurement accuracy of raw data and a warpage measurement test of a bi-material strip to verify the accuracy of evolution properties.     

Measurement of inhomogeneous strain fields by fiber optic sensors embedded in a polymer composite material

Experimental results of strain field measurement in polymer composite specimens by Bragg grating fiber optic strain sensors embedded in the material are considered. A rectangular plate and a rectangular plate with “butterfly” shaped cuts are used as specimens. The results of uniaxial strain experiments with rectangular plates show that fiber optic strain sensors can be used to measure the strains, and these results can be used to calculate the calibration coefficients for fiber optic strain sensors. A gradient strain field is attained in a plate with cuts, and the possibility of measuring this field by fiber optic strain sensors is the main goal of this paper. The results of measurements of gradient strain fields in the plate with cuts are compared with the results obtained by using the three-dimensional digital optic system Vix-3D and with the results of numerical computations based on finite element methods. It is shown that the difference between the strain values obtained by these three methods does not exceed 5%.     

粉尘质量浓度的光纤光栅传感测量技术

粉尘质量浓度是粉尘爆炸的关键因素，针对目前对本质安全、可实时监测预警的粉尘质量浓度测量技术的迫切需求，提出一种基于光纤光栅和光纤准直器的新型测量技术，在阐述其测量理论的基础上，搭建测量和实验装置实物。对200、300和400目这3种粒径规格的小麦粉尘分别开展实验测量，结果表明:所提出的测量技术的光功率输出和粉尘质量浓度呈线性关系；并与标准的称重法得到的粉尘质量浓度开展对比，验证了光纤光栅测量技术的有效性。     

Torsion measurement using fiber Bragg grating sensors

In this paper, the authors study the potential of using fiber Bragg grating (FBG) strain sensors to measure the torsion deformation theoretically and experimentally. FBG sensors are bonded on the surface of a shaft. When the shaft is under torsion, there is strain induced in the FBG sensor and the Bragg wavelength will shift accordingly. According to the wavelength shift and photoelastic properties of the FBG sensor bonded to the shaft, the torsion deformation of the shaft can be obtained. To minimize the measurement error, the optimal direction of the FBG sensor is obtained. The influences of the orientation deviation of the FBG sensor are discussed. The feasibility of this method is demonstrated by experiment, and the test results agree well with the theoretical analysis.     

基于神经网络与光纤传感阵列的结构状态监测方法

以探测机敏复合材料与结构内应变、应力及损伤等物理状态的位置信息为目的．提出了一种新颖的可内埋于材料与结构内作为结构状态监测用的强度调制型光纤传感阵列网络，并采用人工神经网络来处理传感阵列输出的并行分布式传感信号，阐述了适用的Ｋｏｈｏｎｅｎ网模型及其变化形式，给出了仿真实验结果