NEW MEASUREMENT FOR DYNAMIC

A new measurement developed by Fiber Brag grating sensor is used to measure the clearance of structure under vibration environment. The flexible-beam FBG including its design, validation, and measuring inside the assembled joints on a shaking table are introduced. By one flexible slice, there are two FBG sensors encapsulated separately in the slice. Based on this design, the positive and negative strains can make the spectra broaden as the displacement increasing, thus by converting strains to relative displacements, it is derived by calibration data. Subsequently, the normalization of the displacement and strain can be deduced with a good accuracy. Application results: 1) The new measurement by FBG sensor is suitable for the dynamic clearance inside the narrow space without damaging the structure and also has the accurate data compared to traditional methods. 2) This research is based on the high speed of array detector pixels and real-time processing method, which can realize demodulation analysis and data-processing with a dynamic 1000Hz frequency, no image distortion, no data transfer lost. 3) According to the experiment data, the accuracy of the measurements has a relationship with the parameters of the vibration excitation conditions and demodulation phase. Thus the FBG sensor’s size and range should be taken full consideration when it designed for measuring clearance. 4) Factors influencing on the reliability of the FGB sensor are packaging technology, material and encapsulation processing, therefore the further research for the FBG measurement should be focus on the reliability experiment.