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1.
A reliable understanding of the properties of 3-D braided composites is of primary importance for proper utilization of these materials. A new method is introduced to study the mechanical performance of braided composite materials using embedded optic fiber sensors. Experimental research is performed to devise a method of incorporating optic fibers into a 3-D braided composite structure. The efficacy of this new testing method is evaluated on two counts. First, the optical performance of optic fibers is studied before and after incorporated into 3-D braided composites, as well as after completion of the manufacturing process for 3-D braided composites, to validate the ability of the optic fiber to survive the manufacturing process. On the other hand, the influence of incorporated optic fiber on the original braided composite is also researched by tension and compression experiments. Second, two kinds of optic fiber sensors are co-embedded into 3-D braided composites to evaluate their respective ability  相似文献   

2.
分析了分布式光纤传感器测量结果的可靠性,提出从应变系数和温度系数标定到分布式光纤传感器物理量测量以及结果评价的方法,设计了分布式光纤传感器的应变系数和温度系数标定装置,同时分析了应变标定装置的不确定度来源,采用基于光频域反射技术的分布式光纤解调仪进行了实验验证。应变标定范围为-5000με~5000με,温度标定范围为20℃~50℃,第一次测量得到应变系数和温度系数分别为:-6.6775με/GHz和-0.5921℃/GHz。使用获得的应变系数和温度系数再次测量,得到在测量范围内,应变测量相对误差为1%,温度测量相对误差为2%,满足工程应用要求。上述结果表明,设计、发展的数据标定及分析方法可用于分布式光纤传感器应变系数和温度系数的标定。  相似文献   

3.
The active vibration control of a rectangular plate either partially or fully submerged in a fluid was investigated. Piezoelectric sensors and actuators were bonded to the plate, and the assumed mode method was used to derive a dynamic model for the submerged plate. The properties of the piezoelectric actuators and sensors, as well as their coupling to the structure, were used to derive the corresponding equations of their behaviour. The fluid effect was modelled according to the added virtual mass obtained by solving the Laplace equation. The natural vibration characteristics of the plate both in air and in water were obtained theoretically and were found to be consistent with the experimental results, and the changes in the natural frequencies resulting from submersion in fluid can be accurately predicted. A multi-input, multi-output positive position feedback controller was designed by taking the natural vibration characteristics into account and was then implemented by using a digital controller. The experimental results show that piezoelectric sensors and actuators along with the control algorithm can effectively suppress the vibration of a rectangular plate both in air and submerged in a fluid.  相似文献   

4.
埋光纤光栅传感器智能土木结构应变监测   总被引:4,自引:0,他引:4  
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。  相似文献   

5.
The evolution of spatially resolved internal strain/stress during the manufacturing of thermoplastic composites and subsequent relaxation from water intake are evaluated using an in-situ fiber optic sensor corresponding to a coated optical glass fiber with a nominal diameter of 160 μm. Unidirectional carbon fiber-polyamide 6 composites are produced using compression molding with an embedded fiber optic for strain measurement. The distributed fiber optic based strain sensor is placed in an arrangement to capture 0, 45, and 90° strains in the composite to resolve in-plane strain tensor. Strains are monitored in the direction of fiber optic sensor along its length at high resolution during the various stages of compression molding process. Results indicate considerable internal strains leading to residual stress at the end of processing step along the off-axis (45°) and transverse (90°) directions, and small strains in the carbon fiber pre-preg (0°) direction. At the end of compression molding process, an average of 7000 and 10,000 compressive micro-strains are obtained for residual state of strain in the off-axis and transverse direction. Since water/moisture infusion affects the mechanical properties of polyamide-6 matrix resin, these composite panels with embedded sensors targeted for marine applications are monitored in a water bath at 40 °C simulating accelerated testing conditions. Using the same fiber optic sensor based technique, the strain relaxation was observed during water uptake demonstrating in-situ strain monitoring during both manufacturing and subsequent composite implementation/application environment. The technique presented in this paper shows the potential of optimizing time-temperature-pressure protocols typically utilized in thermoplastic manufacturing, and continuous life-cycle monitoring of composite materials using a small diameter and inexpensive distributed fiber optic sensing.  相似文献   

6.
研究Winkler地基上正交各向异性矩形薄板弯曲方程所对应的Hamilton正则方程, 计算出其对边滑支条件下相应Hamilton算子的本征值和本征函数系, 证明该本征函数系的辛正交性以及在Cauchy主值意义下的完备性, 进而给出对边滑支边界条件下Hamilton正则方程的通解, 之后利用辛叠加方法求出Winkler地基上四边自由正交各向异性矩形薄板弯曲问题的解析解. 最后通过两个具体算例验证了所得解析解的正确性.  相似文献   

7.
绞合式光纤应变传感器   总被引:7,自引:0,他引:7  
研究了一种可用于工程结构状态监测的本征型强度调制光纤应变传感器,由两根以上多模光纤相互绞合形成,分析了该传感器的应变传感原理,得到其既能测量拉应变,又有测定压应变的结论,传感器对应变的响应具有良好的线性和重复性、灵敏度高、无迟滞现象,对钢筋拉应变、混凝土压就矿业的实验结果与理论分析一致,表明该传感器是适合土木工程测量、结构状态监测等方面的较为理想的光纤传感器。  相似文献   

8.
This article describes a pseudo-heterodyne demodulation technique for interferometric fiber optic sensors that has a larger measurement range than is currently possible with pseudo-heterodyne demodulation. This sensor demodulation technique has a bandwidth of 30 Hz to 2.5 kHz, is capable of resolving optical phase angles as small as 5×10−4 rad, and has a maximum measurement range of tens of radians in a bandwidth of 30–500 Hz. A comparison between the response obtained from a resistance strain gage and a fiber optic sensor using this demodulation is favorable.  相似文献   

9.
The bending of a cantilever rectangular plate is a very complicated problem in thetheory of plates.For a long time,there have been only approximate solutions for thisproblem by energy methods and numerical methods.since 1979,Prof.F.V.Chang of Tsing Hua University obtained,by the method ofsuperposition,a series of analytic solutions for cantilever rectangular plates under uniformload and concentrated load.In this paper,the two-direction trigonometric series is used to obtain the solution forthe bending of cantilever rectangular plates under uniform load.The obtained results arecompared with the results by the method of superposition.The comparison shows that theresults of these two methods are in good agreement,hence they are mutually confirmed to becorrect.  相似文献   

10.
Global bifurcations and multi-pulse chaotic dynamics for a simply supported rectangular thin plate are studied by the extended Melnikov method.The rectangular thin plate is subject to transversal and in-plane excitation.A two-degree-of-freedom nonlinear nonautonomous system governing equations of motion for the rectangular thin plate is derived by the von Karman type equation and the Galerkin approach.A one-toone internal resonance is considered.An averaged equation is obtained with a multi-scale method.After transforming the averaged equation into a standard form,the extended Melnikov method is used to show the existence of multi-pulse chaotic dynamics,which can be used to explain the mechanism of modal interactions of thin plates.A method for calculating the Melnikov function is given without an explicit analytical expression of homoclinic orbits.Furthermore,restrictions on the damping,excitation,and detuning parameters are obtained,under which the multi-pulse chaotic dynamics is expected.The results of numerical simulations are also given to indicate the existence of small amplitude multi-pulse chaotic responses for the rectangular thin plate.  相似文献   

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