Quantifying Uncertainties in Optical Measurements of Strain

It has not been common practice to calibrate optical systems for measuring full-field strain distributions. Consequently it has not been possible to identify and then cite the uncertainties associated with such measurements. A draft standard on the calibration of optical systems for measuring strain was produced by the European SPOTS project in 2006. The SPOTS standard proposes a reference material, a methodology for calibration and recommendations for quantifying the uncertainties associated with the reference material and the calibration experiment. The reference material generates a reproducible and predictable strain distribution. A comparison between the measured and predicted strain in the gauge section of the reference material allows the uncertainties in the data to be evaluated. A judgment on the acceptability of the calibration can be made by considering these uncertainties together with knowledge of the uncertainty in the reference material. The data also contributes to quantifying the uncertainty in subsequent measurements made with the calibrated instrument.JRC.I.4-Nanotechnology and Molecular Imagin