On the use of the Fourier transform to determine contact curvature distributions in additive manufacturing powders

Abstract

Particle size and shape distributions affect many aspects of powder processing; for example, shape and contact curvature are fundamental to the mechanics of powder spreading, packing, and sintering in powder-bed additive manufacturing. In this paper, we revisit the use of Fourier transforms for detailed shape characterization, including local curvature of particle perimeters and distributions thereof. Fourier transforms describe particles as symbolic functions that are differentiable, enabling direct mapping of curvature. Dynamic image analysis was used to collect 2D particle images of fine metal powders. Two types were compared, one made by gas atomization, and the other by a cold mechanical size reduction process, both suitable for additive manufacturing using laser powder-bed fusion. Global distributions in shape factors including contact curvature were analyzed. Results suggest the utility of curvature distributions as a unique and differentiating shape characteristic.