Identification of dilatancy in green compacted ceramic powder via digital image correlation

Abstract

This paper describes an experimental procedure based on the digital image correlation (DIC) technique to observe pre-failure dilation (a phenomenon known as dilatancy) before rupture in green compacts made of alumina powder. Dilatancy is defined as an increase in the volume occupied by granular materials subjected to shear stresses. This phenomenon occurs when the cohesive forces between the granules are overcome by the loading forces, leading to micro-cracks and an increase in the volume. We demonstrate the advantages of applying the DIC technique to identify the onset of dilatancy through an investigation of the evolution of the volumetric and deviatoric strains during mechanical tests. A cyclic uniaxial compression test was performed with a green compact and the dilatancy was successfully determined using the experimental procedure developed.