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- 2012 (4) (entfernen)
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- Zeitschriftenartikel (2)
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- Fiber Bragg grating (2)
- Strain transfer (2)
- Digital image correlation (1)
- Electronic speckle pattern interferometry (1)
- Fiber Bragg gratings (1)
- Qualification (1)
- Sensors (1)
- Strain gauge (1)
- Surface application (1)
- Validation (1)
Eingeladener Vortrag
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In Germany, the first guideline for the use of fiber Bragg grating strain sensors, 'Optical Strain Sensor based on Fiber Bragg Grating' (Berlin, Germany: Beuth-Verlag, 2010), has been developed by the GESA guideline group of VDI, 'The Association of German Engineers' and published by Beuth-Verlag. This guideline provides the basic specifications of this sensor type and the sensor characteristics, which have to be known for a reliable sensor performance. In conformity to this guideline, experimental investigations on the strain transfer characteristics of fiber Bragg grating patches have been carried out. A comparison between patches and resistance strain gauges during tensile tests and combined temperature and tensile loading was carried out. The evaluated strain gauge factor and the temperature sensitivity of the strain gauge factor have been compared to the manufacturer's data. The overall performance of the patches has been evaluated. The experimental investigations showed that there are considerable disagreements between the manufacturer's specifications and the observed characteristics.
Surface-applied fibre optic strain sensors were investigated using a unique validation facility equipped with application-independent optical reference systems. First, different adhesives for the sensor's application were analysed regarding their material properties. Measurements resulting from conventional measurement techniques, such as thermo-mechanical analysis and dynamic mechanical analysis, were compared with measurements resulting from digital image correlation, which has the advantage of being a non-contact technique. Second, fibre optic strain sensors were applied to test specimens with the selected adhesives. Their strain-transfer mechanism was analysed in comparison with conventional strain gauges. Relative movements between the applied sensor and the test specimen were visualized easily using optical reference methods, digital image correlation and electronic speckle pattern interferometry. Conventional strain gauges showed limited opportunities for an objective strain-transfer analysis because they are also affected by application conditions.
Fasersensorik-Schwerpunkte und -Aktivitäten in der Bundesanstalt für Materialforschung und -prüfung
(2012)
Strain sensors used in practical applications must provide reliable measurement data. To achieve this, sensor systems must be validated by using experimental facilities that enable physically independent statements about the performance of the sensor components. The paper describes qualification and validation procedures using a special facility to qualify surface-applied strain sensors and to achieve reliable sensor results. Based on examples concerning fibre optic strain sensor patches with and without FBG sensors, the determination of the strain gauge factor also under combined thermal and mechanical loading will be presented. These results are the basis for development of guidelines and standards.