The simulation and selection of shapes for the unfolding of grain size distributions

The determination of a grain size distribution from one planar section requires a representative shape that allows the distribution in particle size to be estimated from the size distribution of the particle sections. In this work a simulation has been developed to randomly generate convex polyhedra and calculate the distributions in section properties needed to unfold the particle size distribution into three dimensions. Furthermore a new shape selection process based on a common shape factor is described. The relatively high symmetry polyhedra commonly used to unfold grain size distributions underestimate the grain size compared with the randomly generated polyhedra of the simulation. The latter are thought to be more representative of real grain shapes in that they do not commonly possess pairs of parallel faces.