Non-destructive Evaluation of Composite Pressure Vessel by Using FBG Sensors

In recent years, advanced composite structures are used extensively in many industries such as aerospace, aircraft, automobile, pipeline and civil engineering. Reliability and safety are crucial requirements posed by them to the advanced composite structures be- cause of their harsh working conditions. Therefore, as a very important measure, structural health monitoring （SHM） in-service is deft- nitely demanded for ensuring their safe working in-situ. In this paper, fiber Bragg grating （FBG） sensors are surface-mounted on the hoop and in the axial directions of a FRP pressure vessel to monitor the strain status during its pressurization. The experimental results show that the FBG sensors could be used to monitor the strain development and determine the ultimate failure strain of the composite pressure vessel.

High Sensitivity FBG Pressure Sensor Based on Mechanical Amplifier and Interrogation Using Tunable FBG Filter

A high sensitivity fiber Bragg grating pressure sensor by using mechanical amplifier is demonstrated. The measured pressure sensitivity is -1.80×10 -4 /MPa, which is about two orders of magnitude better than a simple monomode fiber with an in-fiber grating. The resolution of pressure measurement is 0.015 MPa based on interrogation using tunable fiber grating filter.

Temperature Compensation Fiber Bragg Grating Pressure Sensor Based on Plane Diaphragm

Pressure sensors are the essential equipments in the field of pressure measurement. In this work, we propose a temperature compensation fiber Bragg grating （FBG） pressure sensor based on the plane diaphragm. The plane diaphragm and pressure sensitivity FBG （PS FBG） are used as the pressure sensitive components, and the temperature compensation FBG （TC FBG） is used to improve the temperature cross-sensitivity. Mechanical deformation model and deformation characteristics simulation analysis of the diaphragm are presented. The measurement principle and theoretical analysis of the mathematical relationship between the FBG central wavelength shift and pressure of the sensor are introduced. The sensitivity and measure range can be adjusted by utilizing the different materials and sizes of the diaphragm to accommodate different measure environments. The performance experiments are carried out, and the results indicate that the pressure sensitivity of the sensor is 35.7pm/MPa in a range from 0MPa to 50MPa and has good linearity with a linear fitting correlation coefficient of 99.95%. In addition, the sensor has the advantages of low frequency chirp and high stability, which can be used to measure pressure in mining engineering, civil engineering, or other complex environment.

Research on a New Fiber-Optic Axial Pressure Sensor of Transformer Winding Based on Fiber Bragg Grating

Based on the principle of the fiber Bragg grating, a new type of fiber-optic pressure sensor for axial force measurement of transformer winding is designed, which is designed with the structure of bending plate beam, the optimization of the packaging process, and material of the sensor. Through the calibration experiment to calibrate the sensor, the field test results of the Taikai transformer factory show that the sensitivity of the sensor is 0.133 pm/kPa and the repeatability error is 2.7%FS. The data of the fiber-optic pressure sensor in different positions maintain consistent and repeatable, which can meet the requirement of the real-time monitoring of the axial force of transformer winding.

Fiber Bragg grating pressure sensor with enhanced sensitivity

A novel fiber Bragg grating （FBG） pressure sensor with the enhanced sensitivity has been demonstrated. A piston-like diaphragm with a hard core in the center is used to enhance the sensitivity. Both the theoretical analysis and the experimental result show that the radius of the hard core has significant effect on the pressure sensitivity. When the radius of the hard core is 1.5 mm, a pressure sensitivity of 7.23 nm/MPa has been achieved.

Numerical investigation and optimal design of fiber Bragg grating based wind pressure sensor

A wind pressure sensor based on fiber Bragg grating （FBG） for engineering structure was investigated in this paper. We established a transaction model of wind pressure to strain and proposed a method of temperature compensation. By finite element analysis, the basic parameters of the sensor were optimized with the aim of maximum strain under the basic wind pressure proposed in relative design code in China taking geometrical non-linearity into consideration. The result shows that the wind pressure sensor we proposed is well performed and have good sensing properties, which means it is a technically feasible solution.

耐高压光纤Bragg光栅压力传感技术研究

分析了聚合物封装光纤光栅的压力响应特性 ,通过采用特殊聚合物材料将光纤光栅封装于金属套管中 ,并通过在金属套管预涂覆一层软弹性材料 ,以消除封装过程中由于聚合物固化收缩以及聚合物与套管壁粘接与摩擦产生的光纤光栅啁啾化 ,改善了光纤光栅压力响应特性 封装后的光纤光栅压力响应灵敏度为 0 .0 36nm/MP ,具有良好的线性 ,压力测量范围可达 4

A Novel High-Sensitivity Pressure Sensor: Thinned Fiber Bragg Grating with Pressure-Sensing Polymer

Based on thinned fiber Bragg grating and polymer material, we propose a novel high-sensitivity pressure sensor and obtained a new contribution to the pressure sensitivity, which is dependent on the derivative of the effective refractive index （RI） of core mode with respect to the surrounding medium RI, as well as on the relationship between the polymer RI and the pressure; moreover, it is inversely proportional to Young＇s modulus of the polymer material. For the polymer with Young＇s modulus of 1.0 MPa, the total pressure sensitivity 1.54×10-2 MPa-1 can be obtained.

一种差动式光纤Bragg光栅渗压、温度双参量传感器

设计了一种差动式双光纤Bragg光栅渗压、温度双参量传感器。在渗压作用下,波纹管产生一个轴向位移,并传递给等强度悬臂梁的自由端,使等强度悬臂梁产生一个挠度变化,带动粘贴在悬臂梁上下表面的光纤Bragg光栅的中心波长发生移位。通过检测两只光纤Bragg光栅中心波长的差值来获得渗压;通过检测两只光纤Bragg光栅中心波长的平均值来获得环境温度。传感器测试表明,传感器对渗压的灵敏度为1.982 nm/MPa,线性度约为0.97%,重复性为1.5%;传感器对温度的灵敏度为0.009 5 nm/℃,线性度约为3.4%。该传感器利用差动结构并结合适当的数据处理实现了对渗压与温度的双参量检测。

大范围光纤Bragg光栅压力传感器增敏实验研究

鉴于钛合金材料具有低弹性模量、受温度影响小等特性，设计制作了一种以钛合金管作为光纤Bragg光栅应变增敏衬底元件的高压压力传感器件．通过与电阻应变计实时监控的对比，从实验上研究了光纤Bragg光栅的中心波长偏移对调谐压强的响应．结果表明：这种增敏设计，具有良好的线性响应和可重复性，且与理论推导结果吻合较好．增敏后对压力的响应灵敏度可达0．034nm／MPa，测压量程可达0～40MPa，甚至更宽．

焊接结构光纤Bragg光栅土压力传感器设计

针对传统土压力传感器长期稳定性差、抗电磁干扰能力不强以及组网难度大等问题,根据传感器与土介质的匹配原则,设计了一种焊接结构双膜片光纤Bragg光栅(FBG)温度自补偿土压力传感器,可实现温度和土压力2个参量的同时测量。传感器主要由2个膜片与基体组成,膜片与光栅固定柱一次成型,便于加工封装。对传感器灵敏度系数进行了计算分析。根据分析结果,加工封装传感器并对其进行了压力校准及温度自补偿性能实验。实验结果表明:传感器的输出波长分别与温度和压力呈线性关系,压力灵敏度系数为528.1pm/MPa,输出分辨率为0.19%,线性相关度99.988%;在5~45℃内温度灵敏度系数为31.9 pm/℃,线性相关度99.998%,传感器在5~45℃范围内具有良好的温度自补偿能力,其性能参数符合工程应用要求。

新型光纤Bragg光栅微型压力传感器

介绍了一种新型的光纤Bragg光栅微型压力传感器,这种压力传感器采用特殊的结构将作用在光纤横向的压力转换成沿光纤轴向的张力,从而实现对光纤横向压力的高灵敏度测量,传感器对横向压力的灵敏度可达到-4.55×10-3/MPa,比国外同类研究成果高出3个数量级。同时,该微型压力传感器的横向尺寸可做到几百个微米,因此,可以置于很小的空间中对压力进行测量,在工业和军事领域具有广泛的应用前景。

光栅型缸压传感器解调系统设计

为使携带被测量信息的光信号更加真实地还原缸压信号,从光纤感知原理出发分析解调系统构成和工作过程,设计解调缸压信号的电路结构并分析研究参数指标取值。利用Cadence PSpice仿真软件及电路图制版实物试验验证了所做工作的合理性。对所设计电路进行灵敏度分析,确定对电路工作性能影响较大的关键元器件,并预测关键器件取不同容差±5%、±1%、±0.5%、±0.1%时电路性能指标的变化范围,可为研究人员选择最佳器件提供依据。

光纤Bragg光栅压力传感特性研究

提出了以半导体硅材料作为光纤Bragg光栅（FBG）衬底的FBG压力传感密封型结构，并对其压力传感特性进行了研究，结果表明：FBG的中心反射波长漂移对压力呈现良好的线性响应特性，在0-35MPa的测压范围内，压力调谐灵敏度为0．034nm／MPa；有良好的机械性能和稳定性能。通过对实验数据的拟合分析表明：采用这种材料，其中心波长和压力变化有着好的线性拟合度和重复性，且迟滞很小，它们的相关系数都达到0．99，在光传感领域具有实用价值。

双膜结构FBG土压力传感器优化设计及灵敏度分析

为实现桩基础结构安全及其服役状态的监测和有效评估,提出一种双膜结构土压力传感器,以光纤布拉格光栅(fiber Bragg grating,FBG)为传感元件,通过保护结构中增加的温度补偿膜,实现温度作用与外部荷载作用的彻底分离。基于双膜结构土压力传感器的工作原理,讨论了传感器压力灵敏度系数特性。结合有限元分析和实验研究,对灵敏度系数的影响参数展开了系统分析。数值分析结果表明,膜片厚度对压力敏感度系数的影响最大,结构半径和膜片厚度可选取为20 mm和1.8 mm;实验结果表明,在0-2 MPa范围内,压力灵敏度系数达3.32 pm/kPa。

基于光纤光栅的抗偏载压力环传感研究及其工程应用

为解决压力传感器在拉索索力监测中抗偏载能力不足的问题,设计了一种基于光纤光栅的组合式压力环,理论分析了粘贴式光纤光栅传感器与基体之间的应变传递率;根据索力监测量程,对承力支柱的弹性模量、直径、数量及光纤光栅自感知杆件预拉应力提出了设计要求。利用8个准分布式光纤光栅传感器预拉应变的恢复对索力进行监测,消除偏载对测量结果的影响。采用压力试验机对组合式光纤光栅压力环进行循环加载试验,结果表明,组合式光纤光栅压力环能有效监测荷载,其监测灵敏度约为2.2982×10^(-4)nm/kN,线性度误差≤0.821%、迟滞误差≤0.382%、重复性误差≤3.758%、总精度≤3.867%。利用组合式光纤光栅压力环对桥梁的索力张拉进行实时监测,并与油压表读数法、频率法相互验证,分析发现,组合式光纤光栅压力环和频率法监测的索力基本相近,误差在3.4%以内。组合式光纤光栅压力环利用分区承载、预拉应变的恢复实现受压监测,消除偏载弯曲产生的测量误差,提高监测精度高,改变自感知杆件预拉应力和承力支柱数量可实现多种规格拉索的索力监测,降低工程监测成本。

钻孔压灌桩的超弱光纤光栅应变场监测方法

提出了一种在长螺旋钻孔压灌桩中引入超弱光纤光栅的应变场监测方法。分析了超弱光纤光栅多点应变传感原理,设计了一种定点式标距1 m的超弱光纤光栅光缆,对灵敏度进行了标定,在10000με范围内的平均应变灵敏度为1.15 pm/με。在广州市有轨电车试验桩项目中,采用预拉力方式将光缆与钢筋笼结合后埋设,经过28天固化后对多根长螺旋钻孔压灌桩进行了静载测试和分析。试验表明,超弱光纤光栅传感系统工作频率1 Hz,应变精度1可实现对桩基应变场的多点、大量程、高精度的线性监测,验证了超弱光纤光栅传感器在桩基监测中的可行性。

基于光纤光栅传感器的复合材料气瓶应变检测

针对复合材料气瓶应变检测的需求,提出了一种光纤光栅传感器植入碳纤维缠绕铝合金内衬的复合材料气瓶的方法,首先在室温下将光纤光栅传感器粘接在经过喷砂处理的铝合金内衬外表面,然后对粘接了光纤光栅传感器的铝合金内衬进行高温老炼,最后进行碳纤维缠绕和固化。开展了8只光纤光栅应变传感器植入复合材料气瓶的试验,其中6只传感器在复合材料气瓶150℃/1.5 h固化后保持存活,实现了复合材料气瓶固化、水压疲劳、高温试验等过程中的应变检测。结果表明,所提出的方法可以减小内衬的粗糙外表面导致的光纤光栅信号衰减,验证了光纤光栅传感器植入复合材料气瓶进行应变检测的可行性。

一种双面感压式光纤土压力传感器

针对现有的光纤光栅式土压力传感器易因光栅受力不均匀而导致光栅反射谱展宽甚至出现啁啾而降低测量精度等问题,基于菱形金属框架结构和金属化光纤光栅设计制作了一种双面感压式土压力传感器,将光纤光栅直接焊接固定在菱形金属结构对角线的两端,通过菱形金属结构将外界压力放大后作用于光栅两端,使得光栅栅区始终处于悬空且均匀受力状态,避免了光栅受力不均匀导致的光谱展宽及啁啾现象,采用焊接工艺避免了胶粘带来的蠕变、老化、失效等问题,保证了传感器较高的测量精度和较好的长期稳定性。理论分析和实验结果表明,研制的光纤式土压力传感器波长-压力灵敏度系数约为624 pm/MPa,量程为3.5 MPa。

双块式无砟轨道枕上压力监测标定方法

为探寻双块式无砟轨道枕上压力的长期监测方法,以CRTSⅠ型双块式轨枕为研究对象,首次利用埋入式光纤光栅传感器研究了双块式轨枕内部应变值和枕上压力的线性关系.首先,在轨枕制造阶段埋入FRP-OF光纤光栅应变传感器,用于测试轨枕内部应变变化;其次,通过反力架和千斤顶对轨枕进行静力加载标定,分析轨枕表面加载力和轨枕内部应变的线性关系;最后,通过有限元仿真进行验证和修正.结果表明:在轨枕表面施加的载荷和轨枕内部光纤光栅应变传感器的测试值具有良好线性关系,将此线性斜率确定为标定系数(4.90~5.28 kN/με),仿真数据与实测数据的误差在5%以内;对比轨枕在反力架约束和在道床板约束两种不同边界条件工况下的枕内应变,修正了枕上压力计算式,提出了一种基于双块式轨枕内部应变的枕上压力计算方法,并在高速铁路运营线路上测得枕上压力约为30~42 kN;该方法为高速铁路轮轨荷载传递研究、无砟轨道结构的强度计算理论和方法的完善以及列车轮对状态监测提供重要依据.