Visco-elastic sintering kinetics in virgin and aged polymer powders

This work provides a novel discrete element method (DEM) framework for modelling the visco-elastic sintering kinetics in virgin and aged polymer powders. The coalescence of particle pairs, over long times, is described by a combined three-stage model of the sintering process, where each stage is dominated by a different driving force: adhesive contact force, adhesive inter-surface force and surface tension. The proposed framework is implemented in MercuryDPM, an open-source package for discrete particle simulations. To quantitatively calibrate the particle-scale parameters, Bayesian filtering is used. Experimental data on Polystyrene (PS), Polyamide 12 (PA12), and PEEK powders, both virgin and aged, are analysed and confirm over a wide range of times the existence of the three distinct sintering mechanisms. In good agreement with the experimental observations, the estimation of sintering time is achieved with a significant accuracy compared to Frenkel's model. This study provides an efficient and reliable approach for future studies of strength evolution in powder-bed fusion processes.(c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).