Novel ultrasonic in-die measurements during powder compression at production relevant speed
Nov. 1, 2019, midnight
Robert F. Lammens
Karl G. Wagner
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A groundbreaking ultrasonic instrumentation has been successfully integrated into a compaction simulator. This setup utilized a through-transmission configuration with alternating longitudinal and transverse transducers positioned inside Euro-D-modified punches. The text outlines key aspects of the data acquisition process, emphasizing precise displacement measurement and synchronous acquisition of the ultrasonic signal.
The evaluation focused on Vivapur 102 and Di-Cafos A150. Notably, this instrumentation allowed for production-relevant powder densification speeds while maintaining exceptional measurement precision, distinguishing it from other published setups. The maximum ultrasonic speed coincided with maximum density. Materials exhibited significant differences in the decompression phase slope, providing insights into the elasticity and speed sensitivity of powders or formulations without the need for double compression.
The developed setup also facilitates in-die measurements of apparent Young’s modulus and apparent Poisson’s ratio, allowing for their assessment throughout the tableting process. Young’s modulus increased with densification, aligning with literature data. Poisson’s ratio exhibited a linear increase with solid fraction for plastically deforming Vivapur 102, while it remained nearly constant for brittle Di-Cafos A150. This setup enhances mechanistic understanding of deformation factors (e.g., rearrangement, fragmentation, elasticity) and enables the estimation of mechanical compatibility in mixtures. Furthermore, in-die Young’s modulus and Poisson’s ratio prove valuable for compression simulations using finite or discrete element methods.