Quantifying surface deformation around micrometer-scale indents by digital image correlation

Abstract: Indentation tests provide a facile route to gathering strength and stiffness information from small-scale samples, but typically have not been used to systematically assess distributions of surface plastic strain. The objective of the present work is to quantify in-plane plastic strain around micrometer-scale indents via digital image correlation (DIC). We demonstrate the method by comparing pre- and post-indentation surface images, acquired with a scanning electron microscope (SEM). Applying this method to metal composites synthesized by liquid- and solid-metal dealloying, we find that the maximum surface strains around indents do not change with the indentation depth, that strain concentrates preferentially in regions with largest composite constituent dimensions, and that the constituents are not co-deforming. We conclude that the method we have demonstrated is suitable for characterizing the relative propensity of materials to undergo uniform or localized plastic flow. Graphic abstract: [Figure not available: see fulltext.]