Comparison of shearography and optical fibre Bragg grating strain sensors with resistance foil strain gauge measurements

Abstract

The benchmarking of two optical strain measurement techniques, shearography and fibre Bragg grating (FBG) sensors, against theoretical strain calculations and resistance foil strain gauges (RFSG) is described. The test object used for the surface strain measurements was an ABS pipe that was hydrostatically loaded. A multi-component shearography instrument, capable of full surface strain measurement was used to determine the displacement gradients, from which the strain components were calculated. Six surface mounted wavelength division multiplexed FBG sensors were used to measure the axial and the hoop strains. RFGSs located on the surface of the pipe, adjacent to the FBGs, were used for comparison. Good agreement between theory and the axial and hoop strains determined by the different techniques was found.