Micromechanical analysis of inclusions in particulate media using digital photo stress analysis tomography

An experimental study aimed at sensing the stress distribution characteristics of inclusions inside particulate assemblies subjected to axial compaction is presented here. The particulate assemblies are made of powders and grains in which photo elastic inclusions are embedded along the central axis of the assemblies at different elevations. Digital photo stress analysis tomography is used to obtain the contours of maximum shear stress distribution and the direction of major principal stress within the inclusions under the external loading. Using this, an analysis is performed for understanding the implications of using Hertz theory based discrete element modelling for simulating stresses in relatively big inclusions surrounded by particulates. In the case of the inclusions surrounded by the grains, the location at which peak value in maximum shear stresses occurs within in the inclusions deviates from that of Hertzian analysis. This effect is dominant in the case of inclusions residing close to the loading surface. Unlike granular materials, shear stress distribution characteristics of inclusions in powder surroundings tend to display continuum-like behaviour under external compression and points to the need for a deeper understanding of the effects of surrounding materials in particulate beds with inclusions.