Densification of visco-elastic powders during free and pressure-assisted sintering

This study presents an advanced computational model designed for the analysis of the densification process in visco-elastic powders during sintering. The model incorporates thermo-mechanical aspects into the discrete element method (DEM), and a thermo-rheological model to describe the rate of sintering when visco-elastic particles are in contact at variable temperatures. First, a novel contact model is developed and calibrated using experimental data obtained from dilatometric experiments on PA12 pellets. The calibration process involves measuring the linear (axial) shrinkage of the powder compact pellets with dilatometers and employs Bayesian filtering to identify the model parameters. The calibrated model accurately characterizes the linear shrinkage observed in the PA12 pellets. Subsequently, the study delves into the influence of various process parameters on the evolution of bulk density, commonly referred to as relative density. These investigations provide valuable insights into the impacts of maximum process temperature, holding time process duration, and external pressure, for which our model is capable of providing qualitative descriptions. The findings support the notion that longer process durations and the application of higher external pressure are the main drivers of densification, aligning with expectations in metallurgy techniques. This work offers a predictive DEM tool for computing the densification of pellets made of visco-elastic powders.