基于相移布喇格光纤光栅的折射率传感实验研究

利用图解法求解光纤特征方程,获得腐蚀过程和传感过程中光纤光栅的光谱特性,设计了光纤光栅的部分腐蚀方案,采用氢氟酸溶液腐蚀制作相移布喇格光纤光栅。对光纤光栅进行部分腐蚀,将形成相移光纤光栅。根据相移光纤光栅的特性,讨论了利用反射光光强解调的方式,该方式具有结构简单且对温度不敏感的优点。     

FBG智能传感器及其在土木工程中的应用研究

光纤光栅传感器已经越来越得到土木工程界的认可,并应用到了实际工程.针对大型土木工程结构长期健康监测的变形监测需要,在光纤光栅传输理论的基础上,分析了光纤光栅应变与温度传感特性以及光纤光栅应变传感的温度补偿原理和方法;研制开发出满足工程应用的光纤光栅封装传感器、FRP-OFBG复合智能筋、光纤光栅智能拉索;此外,考虑传感器开发和工程应用的需要,研究了光纤光栅应变传感的界面传递机理和误差修正.最后,建立了光纤光栅智能监测系统,并成功地将光纤光栅传感器应用到实际桥梁结构的施工与运营监测.     

复合材料胶层光纤布格光栅应变监测优化配置研究

航空航天用复合材料粘接胶层在制造和服役过程中不可避免会产生各种缺陷和损伤。针对其粘接胶层缺陷和损伤检测,基于光纤光栅应变传感原理,提出一种针对复合材料胶接层结构应变监测的光纤光栅传感网络优化配置的方法。通过仿真和实验研究了埋入复合材料构件胶接层的光纤布拉格光栅传感器在静载作用下的敏感区域分布特性,分析了载荷位移与布拉格波长漂移的关系,建立符合光纤布拉格光栅传感器实际特点的探测模型,采用粒子群优化算法进行光纤光栅传感网络的优化布置,研究结果表明光纤布拉格光栅传感器位置经优化后,覆盖率得到明显提高。     

光纤光栅传感技术在桥梁静载试验中的应用

光纤光栅传感技术作为工程结构监测的一种全新方法,因其具有较高的性价比而备受青睐;以桥梁静载试验为例,详细介绍了光纤光栅传感原理和布设工艺;根据静载试验得出的应力应变数据对桥梁健康状况加以分析表明:光纤光栅传感技术性能稳定、数据能较好反映出实桥在荷载作用下的健康状况。     

根键式桥墩的光纤光栅传感网络应用研究

论述了光纤光栅传感网络在根键式桥墩应变分布实验测量中的应用研究。根据对桥墩应变点分布情况的有限元法分析,在大桥成桥过程中成功地布置了相适应的光纤光栅传感网络。传感网络共分10层,每层布置8个光纤光栅应变传感器和1个温度传感器,布设的传感器在桥墩的静载荷实验过程中监测结构层的状态。监测结果表明：所布设的光纤光栅传感网络在桥墩12次加载,每次载荷2352kN（240t）的过程中,能正确反映桥墩结构层面的变化,为桥梁的安全载荷运营提供了可靠的依据。     

基于双折射效应的光纤光栅称重方法研究

与通常的光纤光栅传感器原理不同,本文基于光纤在外界径向载荷作用下产生的双折射效应为原理,建立了一套简单的称重实验装置,并对其检测原理进行了详细的分析。实验表明,这种光纤光栅称重传感器适合大载荷情况的重量检测问题,特别适合于公路计重收费系统中对车辆载重的监测领域,其称重灵敏度可达5kg。     

Fe-C膜光纤光栅锈蚀传感器在模拟海洋环境中的特性研究

研究了一种基于与钢筋成分相似的Fe-C膜光纤光栅锈蚀传感器,在模拟海洋环境3.5%NaCl溶液中进行锈蚀监测,同时与电化学监测比较。对Fe-C膜进行电子探针、XRD和SEM测试,阐述了传感器的结构和原理。实验结果表明:光纤锈蚀传感器在2.5d达到最大漂移量430pm,锈蚀10d敏感膜出现脱落,波长发生回落。与电化学监测相比,光纤锈蚀传感器能够实现长期监测,并获得锈蚀时间、锈蚀速率和锈蚀程度等锈蚀状态,对钢结构的实时在线监测具有重要意义。     

混凝土结构的光纤光栅智能监测技术

根据混凝土结构的内部应变监测需要，提出了光纤光栅管式封装应变传感器，并对其传感特性进行了研究；探讨了光纤布拉格光栅传感元件在混凝土结构中的布设工艺，并用光纤光栅监测了水泥净浆的固化过程；用管式封装光纤光栅与裸光栅对钢筋温凝土梁进行了应变监测；最后将光纤光栅传感器成功地应用于黑大公路大桥。     

一种简易测试光纤光栅应变测量系统的方法

针对光纤光栅应变测量系统应用测试问题,基于悬臂等强度梁应变实验,对比理论计算、光纤光栅应变传感器及电阻应变片的三种应变测量方法,得出光纤光栅应变测量系统具有较好的可靠性和准确性。以国外可靠光纤光栅应变测量系统为参照,提出了简易测量光纤光栅应变传感器和光纤光栅传感分析仪性能的方法。针对准分布式监测问题,主要分析了光分路器对光纤光栅传感应变测量的影响。上述分析为光纤光栅应变测量系统在工程中的应用提供充分依据。     

基于光纤光栅传感器的复合材料层合板冲击能量研究

复合材料结构较容易产生结构表面无法探测到的低速冲击损伤。试验利用光纤复合材料结构中布拉格光纤光栅传感器受到低速冲击后光栅中心波长随应力变化这一特性,在恒温下用布拉格光纤光栅传感器对复合材料智能结构受到的低速冲击能量给出判别,并对通过光纤光栅解调仪采集下来的低速冲击信号进行频谱分析。在计算冲击信号所有能量等级的频谱峰值后,给出可以界定能量等级的频谱峰值临界值,利用其来判别低速冲击能量等级。试验表明布拉格光纤光栅传感器可以监测复合材料受到冲击的信号,能够对复合材料结构低速冲击进行能量等级判断研究     

Correlation between corrosion pits and stresses in Al alloys

Pitting corrosion is commonly observed in a wide range of aluminum alloys that are being used for aerospace applications. There is a need to study the stress environment around pits in order to predict the nucleation of cracks. The objective of this study is to investigate the correlation between pits and stresses in aluminum alloys. Corrosion experiments were carried out on aluminum 2024-T3 alloy samples and imaged through Atomic Force Microscopy (AFM) to obtain the pit profiles. An analysis procedure was developed using CAD and finite element analysis to predict stresses resulting from corrosion pits. Based on the analysis, it was observed that the stress distribution and levels on the corroded surface varied due to irregularity in the corrosion process. The results obtained indicate that the stress initially increases and reaches a plateau with increasing corrosion time. From these stresses it is possible to estimate the initiation of cracks, from which the life can be estimated for failure in the material.     

新型航空T-31钛合金导管连接件在模拟服役环境中的抗腐蚀性能研究

使用自行研制的航空导管连接件腐蚀试验系统,研究了新型航空T-31钛合金导管连接件在模拟服役环境中的气密性、油压气密性以及应力腐蚀、表面腐蚀等综合性能.对这种钛合金导管连接件在高温盐水溶液浸泡与烘烤循环条件下的表面腐蚀及应力腐蚀行为进行了评价;初步探讨了在模拟服役环境中,这种钛合金发生腐蚀的机理.并比较研究了导管材料1Cr18Ni9Ti与连接件钛合金在6%NaCl水溶液中的电偶腐蚀敏感性.研究发现,T-31钛合金导管连接件在模拟服役环境中只在应力集中处发生轻微孔蚀,在试验应力水平下,无应力腐蚀倾向,具有良好的耐蚀性能;并证明,腐蚀介质通过钛合金阳极化膜层小孔渗入基体对基体造成轻微腐蚀,试验应力水平未造成孔蚀发生处裂纹形核;电偶腐蚀试验进一步说明1Cr18Ni9Ti / T-31电偶对有很小的电偶腐蚀电流,用它们制备的导管及导管连接件能安全地进行偶接.     

2024铝合金的一种新时效制度

通过对２０２４铝合金在不同时效制度下硬度和导电率的测试及统计分析,提出了用于替代室温下自然时效的一种新时效制度,对两种时效制度下的２０２４铝合金进行了拉伸、疲劳、腐蚀、疲劳裂主展速率和扩展寿命的对比试验及统计分析,证明两种时效下的材料机械性能无显著差异,新时效制度的２０２４铝全金完全满足适航要求,这 新时效制度可大在缩短飞机结构停场修理时间,给飞机维修公司和航空公司带来较高的经济效益。     

Evaluation of the Effects of Corrosion on Fatigue Life of Clad Aluminum Alloy 2024-T3-Riveted Lap Joints with Acoustic Emission Monitoring

Corrosion affects the fatigue life of clad aluminum alloy-riveted lap joints, such as those found on an aircraft fuselage structure. Single-, double-, and triple-column-riveted lap joint specimens were fabricated and corroded in a Q-Fog accelerated corrosion chamber for five months using an ASTM G85-A5 prohesion test. Specimens were taken out of the chamber every 4?weeks, and the corrosion products which had been deposited on them were removed by immersion in concentrated nitric acid. For each corroded specimen, the mass loss with corresponding corrosion rate was determined. The specimens were fatigue loaded to failure on an MTS Universal Testing Machine with acoustic emission monitoring. Results indicate that exposure of lap joint specimens to this corrosive environment increased corrosion (mass loss), corrosion rate, and significantly reduced fatigue life. For a prolonged exposure in the corrosive environment, the fatigue life was reduced to zero, which has significant implication for aging aircraft. Acoustic emission monitoring successfully detected fatigue failure. Two failure modes, multisite crack damage and shear of the rivets, were observed.     

Simple high-resolution wavelength monitor based on a fiber Bragg grating

A compact and low-cost device for monitoring the peak wavelength of single-peak spectral distributions is presented. The system is based on the transmission properties of a fiber Bragg grating when its period is modulated. Different types of optical signal, such as the emission of distributed-feedback lasers and the reflection of a broadband optical source produced by fiber gratings used in sensor systems, can be measured with this device. We demonstrate that a high wavelength resolution of micro 1 pm can be achieved and that our proposal can be used for real-time monitoring.     

铝合金船舶的腐蚀防护技术现状与展望

针对国内外铝合金船舶的船体、空舱、海水管路系统、艉板法兰等部位的铝合金腐蚀现状进行了调研分析,发现船体基本采用涂料+铝合金牺牲阳极的方法进行保护,效果良好;而空舱、海水管路系统和艉板法兰等部位,却因防腐措施不到位分别存在一定的腐蚀问题。文章结合青岛海洋腐蚀研究所多年积累的铝合金实海腐蚀研究资料,在对相应部位腐蚀问题客观分析的基础上,分别对铝合金船舶的牺牲阳极阴极保护、防腐防污涂层保护、微弧氧化处理和电绝缘保护等腐蚀防护技术,在使用过程中存在的问题以及相应应对措施进行了分析总结,同时对铝合金船舶各项腐蚀防护技术的发展前景以及需要解决的问题进行了展望。     

Multiplexed Long-Base Flexible Optical Fiber Extensometers and Temperature Bragg Sensors Interrogated by Low-Coherence Interferometry

We present a novel concept of quasi-distributed flexible optical fiber extensometers fully compensated from thermal variations. Developed for structural health monitoring applications, the sensors are composed of a combination of intrinsic Fabry-Perot cavities as long-base extensometers, and point-like Bragg gratings inserted along the same fiber used as temperature sensors. This configuration enables a high degree of multiplexing, thus quasi-distributed sensing, and very efficient temperature compensation. Both types of sensors are read by a fiber-optic low-coherence interferometer, used in an original way to measure simultaneously the length variations of the cavities and the wavelength shifts of the Bragg gratings. Finally, we present the experimental validation of the whole measurement system, suitable for concrete structures instrumentation, as it includes an original optical fiber sheath packaging the optical fiber as a flexible sensor.     

Interaction between sulfate-reducing bacteria and aluminum alloys——Corrosion mechanisms of 5052 and Al-Zn-In-Cd aluminum alloys

Microbiologically influenced corrosion caused by sulfate-reducing bacteria(SRB) poses a serious threat to marine engineering facilities.This study focused on the interaction between the corrosion behavior of two aluminum alloys and SRB metabolic activity.SRB growth curve and sulfate variation with and with aluminum were performed to find the effect of two aluminum alloys on SRB metabolic activity.Corrosion of 5052 aluminum alloy and Al-Zn-In-Cd aluminum alloy with and without SRB were performed.The results showed that both the presence of 5052 and Al-Zn-In-Cd aluminum alloy promoted SRB metabolic activity,with the Al-Zn-In-Cd aluminum alloy having a smaller promotion effect compared with 5052 aluminum alloy.The electrochemical results suggested that the corrosion of the Al-Zn-In-Cd aluminum alloy was accelerated substantially by SRB.Moreover,SRB led to the transformation of Al-Zn-In-Cd aluminum alloy corrosion product from Al(OH)3 to Al2 S3 and NaAlO2.     

Proposal of an active composite with embedded sensor

Though advanced composites with embedded actuator materials such as shape memory alloys and piezo ceramics have been developed as active materials, another one by making use of thermal deformation of composites was proposed and an active laminate was prepared as an example by hot-pressing of aluminum plate as material of high coefficient of thermal expansion (CTE), uni-directional carbon fiber reinforced plastics (CFRP) prepreg as low CTE material and electric resistance heater, polymer adhesive film as insulator between them, and copper foils as electrodes. Actuation of this laminate is different from that of bimetal because CTE of the CFRP layer is strongly anisotropic due to directionality of its reinforcement fiber. As CTEs of the CFRP layer and the aluminum plate in the fiber direction are quite different from each other though they are close to each other in the transverse direction, smooth and uni-directional actuation becomes possible. In this study, its fundamental performances such as shape change and output force were observed and evaluated, and after establishment of its fabrication, an optical loss type sensor was formed in the active composite, by embedding multiply pre-notched optical fiber in the CFRP layer and breaking it at the pre-notches under bending, followed by lamination on aluminum plate with adhesive. As the sensing part can be formed inside the matrix without any complicated processes, a robust and low cost sensor is obtained. From the results, it becomes clear that: (1) curvature of the active composite linearly changes as a function of temperature between room temperature and its hot pressing temperature by electric resistance heating of the CFRP layer and cooling, (2) its output force against a fixed punch during heating from room temperature up to around glass transition temperature of the resin phase almost linearly increases with increasing temperature, (3) the multiply pre-notched, embedded and fractured optical fiber works as a sensitive sensor for monitoring the curvature of the active composite.     

高阻尼铝基复合材料在海水中的腐蚀行为

研究了高阻尼铝基复合材料在海水中的腐蚀行为,本实验所用高阻尼铝基复合材料是以6061铝合金为基体,加入SiC颗粒和石墨粉,用粉末冶金方法制备的。测定了高阻尼铝基复合材料在海水中的腐蚀速率度、电极电位和极化曲线,并通过与基体金属的对比来描述它的腐蚀特性。实验表明,在海水介质中,高阻尼铝基复合材料的耐蚀性能比6061铝合金差,孔蚀倾向大。在海水介质中使用高阻尼铝基复合材料必须加以保护。