Development of an in situ method for measuring elastic and total strain fields at the grain scale with an estimation of accuracy

Identifying the parameters of a crystal plasticity model requires the use of grain scale experimental data. The objective of our work is to develop a robust procedure to identify the model using information at the scale of the crystals. In this study, an in situ experimental measurement has been developed for the parameter identification of crystal plasticity models. During the experimental stage, the total and elastic strain fields of an Al-alloy specimen with around 12 grains were measured at the same time. The total strain fields were determined by digital image correlation. For this, a speckle-painting was applied on the sample surface which was tracked to derive the total deformation of the specimen surface under loading. The elastic strains were calculated from X-ray diffraction measurements. Yet certain experimental difficulties had to be solved in order to achieve these simultaneous measurements. Besides results and analysis, the corresponding uncertainties during each measurement were quantified as well.