The Research On Large Stain Measurement Based On Polymer Optical Fiber

Measurement of large strain has important significance in the research of Aircraft wing Tensile, steel tube blasting, earthwork fabric, new polymer Materials and limit design of Structural Materials. optical fiber strain sensor is one of the world's widely used sensor, has many advantages compared with electrical sensors, such as not summit with the interference of the electromagnetism field and can be in bad environment normal work., high sensitivity, small size, excellent insulating property, and can implement distributed measurement. It has been widely used in construction, petroleum and chemical industry. Plastic optical fiber has excellent resistance to irradiation performance, low modulus, relatively soft, large diameter, larger numerical aperture large, easy-to-connect and coupling, light weight, lower cost advantages.Measuring large strain as the target, Plastic optical fiber will be applied to large strain measurement technology. Through theoretical analysis and experimental research, a new way to measure large strain is explored based on plastic optical fiber. Main contents include the following:(1) Theoretical Analysis of polymer optical fiber large strain sensor based on intensity modulation. The factors that cause light transmission loss in polymer optical fiber are analyzed. The bend loss of polymer optical fiber is studied detailed and the relation has been built. Using the differential equation, A mathematical model between strain and fiber's bend loss of ideal structure sensor is established. The factors that impact the sensitivity of sensor, such as fiber diameter and numerical aperture, are analyzed. The actual structure of the sensor and the decisive factors of the sensor's sensitivity and linearity performance are analyzed.(2) A large strain measurement system is established. The noises of the intensity modulation measuring system are analyzed. The functional modules include light souse driving power, coupling light path, optic-electric conversion and A/D acquisition card are designed. The system has a good performance on eliminating and reducing various noises and meets the requirements of measurement.(3) Experimental studies of polymer optical fiber large strain sensor were completed. The experiment mainly includes two parts. Firstly Different light sources, different sensor structures were studied. A new type of large strain sensor is explored by analyzing and comparing experimental results. It has simple structure, good linearity, high sensitivity and able to achieve large strain measurement. Secondly, the performances of sensors including stability, repeatability, hysteresis and dynamic characteristics have been studied detailed.(4) Exploration and Research of multi-point large strain distributed measurement. The distributed measurement of the strain has important significance. Through the research of representational two points'large stain measurement by using space division multiplexing technology, the study explored the sensors for distributed large strain measurement is feasible.Through research, a new large strain sensor based polymer optical fiber is successfully explored. Its measuring range can reach more than 16%. It has good linearity, stability and repeatability. It has a good application prospect. Study on the two-points spatial division multiplexing measurement shows that the presented sensor can easily realize the distributed measurement and it has great application potential.