Estimation of microscale strain fields in a pearlitic steel using DIC and in-situ SEM

Paper in proceeding, 2014

In this contribution the Digital Image Correlation (DIC) technique is used to identify strain fields within a pearlitic microstructure from in-situ obtained SEM images. Typically this is done using a synthetic speckle but in this study the intensity field variations, related to the microstructure of pearlite, are used as a natural speckle. As a means to avoid subsets with inadequate information content (in terms of intensity field variations) a tracebility criterion is introduced. This criterion is based on the eigenvalues of the Hessian of the autocorrelation function. A pertaining algorithm, which can be used to identify high quality subsets (in terms of tracebility) within a certain Region Of Interest (ROI), is also presented. By using the obtained irregular subsets grids together with synthetically deformed images the displacement and deformation gradient errors (both local and average) are studied as a function of the applied loading for various subset sizes.