An optical fiber strain sensor utilizing the mode-mode interference of LP01x, and LPJ11x modes in bow tie optical fibers is described. The heterodyne interference caused by frequency modulation of laser diode (LD) wit...An optical fiber strain sensor utilizing the mode-mode interference of LP01x, and LPJ11x modes in bow tie optical fibers is described. The heterodyne interference caused by frequency modulation of laser diode (LD) with ramp injection current is used to realize the detection of linear phase. Experimental results show a resolution of about 2% of one fringe corresponding to a strain of 2.9m.展开更多
The smart composite structure is a new type of structure developed in recent years. It can be used in aircraft or some other important devices. The smart composite structure in which some sensors, actuators and other ...The smart composite structure is a new type of structure developed in recent years. It can be used in aircraft or some other important devices. The smart composite structure in which some sensors, actuators and other components are embedded can perform the tasks such damage evaluation, strain measurement, changing stress and suppressing vibration by itself. In the Performance of the tasks above, many parameters must be measured, among which the measurement of strain field is very important. In this paper, some distributed and quasi-distributed embedding optic fiber strain sensors are introduced, and their specialities are discussed.展开更多
The distributed strain sensor has significant application in real time measurement of strain status for large and important engineering structures such as aircraft, bridge and dam. In this paper, a quasi distributed...The distributed strain sensor has significant application in real time measurement of strain status for large and important engineering structures such as aircraft, bridge and dam. In this paper, a quasi distributed optical fiber strain sensor system is set up using optical time domain reflect technique. The local strain sensors based on a novel microbend configuration are designed and applied to measure local strains along the optical fiber. As the result of the experimental research, the microbend sensors show high sensitivity, good linearity and repeatability in certain operation range.展开更多
For long-distance water conveyance shield tunnels in operation,the high internal water pressure may cause excessive deformation of composite linings,affecting their structural integrity and serviceability.However,the ...For long-distance water conveyance shield tunnels in operation,the high internal water pressure may cause excessive deformation of composite linings,affecting their structural integrity and serviceability.However,the deformation and failure characteristics of lining structures under internal water pressure are not well investigated in the literature,particularly for three-layer composite linings.This study presents an in situ experimental investigation on the response of two types of composite linings(i.e.separated and combined lining structures)subjected to internal pressures,in which a fiber optic nerve system(FONS)equipped with distributed strain and displacement sensing nerves was employed to monitor the performance of the two composite linings during testing.The experimental results clearly show that the damage of the tunnel lining under different internal pressures was mainly located in the self-compaction concrete layer.The separated lining structure responded more aggressively to the variations in internal pressures than the combined one.Moreover,two evaluation indices,i.e.radial displacement and effective stiffness coefficient,are proposed for describing the changes in the structural bearing performance.The effective stiffness coefficients of the two types of lining structures were reduced by 39.4%and 29.5%,respectively.Considering the convenience of field monitoring,it is suggested that the average strains at different layers can be used as characteristic parameters for estimating the health conditions of lining structures in service.The analysis results provide a practical reference for the design and health evaluation of water conveyance shield tunnels with composite linings.展开更多
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 compos...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 to measure the internal strain. Experimental results show that multiple optic fiber sensors can be co-braided into 3-D braided composites to determine their internal strain which is difficult to be fulfilled by other current existing methods.展开更多
A novel method of measuring non-uniform strain along a fiber Bragg grating(FBG) using optical frequency domain reflectometry(OFDR) is proposed and experimentally demonstrated. This method can overcome the problems of ...A novel method of measuring non-uniform strain along a fiber Bragg grating(FBG) using optical frequency domain reflectometry(OFDR) is proposed and experimentally demonstrated. This method can overcome the problems of traditional non-uniform strain measurement methods for FBGs, i.e., the likelihood of chirping and multiple peaking in the spectrum when FBG is subjected to inhomogeneous strain fields. Wavelength interrogation is realized by OFDR with a narrow-line-width tunable laser as the optical source. When non-uniform strain distributions along areas adjacent to structural damage are measured by this method, good agreement is obtained between measurements and theoretical simulation results.展开更多
文摘An optical fiber strain sensor utilizing the mode-mode interference of LP01x, and LPJ11x modes in bow tie optical fibers is described. The heterodyne interference caused by frequency modulation of laser diode (LD) with ramp injection current is used to realize the detection of linear phase. Experimental results show a resolution of about 2% of one fringe corresponding to a strain of 2.9m.
文摘The smart composite structure is a new type of structure developed in recent years. It can be used in aircraft or some other important devices. The smart composite structure in which some sensors, actuators and other components are embedded can perform the tasks such damage evaluation, strain measurement, changing stress and suppressing vibration by itself. In the Performance of the tasks above, many parameters must be measured, among which the measurement of strain field is very important. In this paper, some distributed and quasi-distributed embedding optic fiber strain sensors are introduced, and their specialities are discussed.
文摘The distributed strain sensor has significant application in real time measurement of strain status for large and important engineering structures such as aircraft, bridge and dam. In this paper, a quasi distributed optical fiber strain sensor system is set up using optical time domain reflect technique. The local strain sensors based on a novel microbend configuration are designed and applied to measure local strains along the optical fiber. As the result of the experimental research, the microbend sensors show high sensitivity, good linearity and repeatability in certain operation range.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.42225702 and 42077235)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX22_0162)the scientific research project of Guangdong Yue Hai Pearl River Delta Water Supply Co.,Ltd.The authors thank Guangqing Wei,Lixiang Jia,and Zhen Zhang,all of Suzhou Nanzee Sensing Co.,Ltd.,for their assistance in the tests.The valuable suggestions provided by Professor Baojun Wang,Nanjing University,are also gratefully acknowledged.
文摘For long-distance water conveyance shield tunnels in operation,the high internal water pressure may cause excessive deformation of composite linings,affecting their structural integrity and serviceability.However,the deformation and failure characteristics of lining structures under internal water pressure are not well investigated in the literature,particularly for three-layer composite linings.This study presents an in situ experimental investigation on the response of two types of composite linings(i.e.separated and combined lining structures)subjected to internal pressures,in which a fiber optic nerve system(FONS)equipped with distributed strain and displacement sensing nerves was employed to monitor the performance of the two composite linings during testing.The experimental results clearly show that the damage of the tunnel lining under different internal pressures was mainly located in the self-compaction concrete layer.The separated lining structure responded more aggressively to the variations in internal pressures than the combined one.Moreover,two evaluation indices,i.e.radial displacement and effective stiffness coefficient,are proposed for describing the changes in the structural bearing performance.The effective stiffness coefficients of the two types of lining structures were reduced by 39.4%and 29.5%,respectively.Considering the convenience of field monitoring,it is suggested that the average strains at different layers can be used as characteristic parameters for estimating the health conditions of lining structures in service.The analysis results provide a practical reference for the design and health evaluation of water conveyance shield tunnels with composite linings.
基金Project supported by the Aeronautic Science Foundation of China (No. 01G52075) the Outstanding Youth Foun-dation of Jiangsu Province (No. BK2002416).
文摘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 to measure the internal strain. Experimental results show that multiple optic fiber sensors can be co-braided into 3-D braided composites to determine their internal strain which is difficult to be fulfilled by other current existing methods.
基金supported by the National High Technology Research and Development Program of China under Grant No.2012AA041203
文摘A novel method of measuring non-uniform strain along a fiber Bragg grating(FBG) using optical frequency domain reflectometry(OFDR) is proposed and experimentally demonstrated. This method can overcome the problems of traditional non-uniform strain measurement methods for FBGs, i.e., the likelihood of chirping and multiple peaking in the spectrum when FBG is subjected to inhomogeneous strain fields. Wavelength interrogation is realized by OFDR with a narrow-line-width tunable laser as the optical source. When non-uniform strain distributions along areas adjacent to structural damage are measured by this method, good agreement is obtained between measurements and theoretical simulation results.
