Permeability is a key powder property for many industrial applications as it affects the flowability during powder handling and the quality of the final product.Indeed,the ability of air to pass through a powder bed,q...Permeability is a key powder property for many industrial applications as it affects the flowability during powder handling and the quality of the final product.Indeed,the ability of air to pass through a powder bed,quantified by permeability,is decisive for die or bag filling,dry powder inhalers,silo discharge,pneumatic transport,fluidized bed,etc.Usually,the permeability is measured on a powder bed subjected to high consolidation stresses and without the possibility to control the packing fraction of the powder.In the present study,we show how GranuPack measurement can be combined with a permeability measurement cell to measure the permeability at low consolidation and for various packing fractions,which correspond to many process conditions.A selection of usual powders(pharmaceutical excipients and abrasives)has been tested and the results highlight how the permeability can be used to obtain additional information about powder behavior.For that,a two levels analysis is proposed:an entry-level based on straightforward parameters like initial and final(after the tapping process)permeability and a more advanced level based on two new metrics.These metrics are the permeability ratio and the rate of variation of permeability.These parameters are directly related to the powder cohesiveness and hence can be used to complement the classical flowability indexes.展开更多
A Discrete Element Method model,including interparticle cohesive forces,was calibrated and validated to develop a tool to predict the powder layer’s quality in the powder bed fusion process.An elastic contact model w...A Discrete Element Method model,including interparticle cohesive forces,was calibrated and validated to develop a tool to predict the powder layer’s quality in the powder bed fusion process.An elastic contact model was used to describe cohesive interparticle interactions.The surface energy of the model particles was estimated by assuming that the pull-off force should provide the strength of the material evaluated at low consolidation with shear test experiments.The particle rolling friction was calibrated considering the bulk density of the layer produced by the spreading tool.The model was validated with the experiments by comparing the wavelet power spectra obtained with the simulations with those of the experimental layers illuminated by grazing light.The calibration proposed in this study demonstrated superior performance compared to our previous methods,which relied on measuring the angle of repose and unconfined yield strength.展开更多
文摘Permeability is a key powder property for many industrial applications as it affects the flowability during powder handling and the quality of the final product.Indeed,the ability of air to pass through a powder bed,quantified by permeability,is decisive for die or bag filling,dry powder inhalers,silo discharge,pneumatic transport,fluidized bed,etc.Usually,the permeability is measured on a powder bed subjected to high consolidation stresses and without the possibility to control the packing fraction of the powder.In the present study,we show how GranuPack measurement can be combined with a permeability measurement cell to measure the permeability at low consolidation and for various packing fractions,which correspond to many process conditions.A selection of usual powders(pharmaceutical excipients and abrasives)has been tested and the results highlight how the permeability can be used to obtain additional information about powder behavior.For that,a two levels analysis is proposed:an entry-level based on straightforward parameters like initial and final(after the tapping process)permeability and a more advanced level based on two new metrics.These metrics are the permeability ratio and the rate of variation of permeability.These parameters are directly related to the powder cohesiveness and hence can be used to complement the classical flowability indexes.
基金supported by MATHEGRAM.Marie SKŁODOWSKA-CURIE Innovative training network MATHEGRAM is funded through the People Programme(Marie SKŁODOWSKACURIE Actions)of the European Union’s Horizon 2020 Programme H2020 under REA grant agreement No.813202.
文摘A Discrete Element Method model,including interparticle cohesive forces,was calibrated and validated to develop a tool to predict the powder layer’s quality in the powder bed fusion process.An elastic contact model was used to describe cohesive interparticle interactions.The surface energy of the model particles was estimated by assuming that the pull-off force should provide the strength of the material evaluated at low consolidation with shear test experiments.The particle rolling friction was calibrated considering the bulk density of the layer produced by the spreading tool.The model was validated with the experiments by comparing the wavelet power spectra obtained with the simulations with those of the experimental layers illuminated by grazing light.The calibration proposed in this study demonstrated superior performance compared to our previous methods,which relied on measuring the angle of repose and unconfined yield strength.
