Relating Compaction Performance and Behavior to Process Conditions

Executive Summary

During the second year of this project we focused on the following activities:

• A detailed study of the force displacement for high densities was conducted as part of a parallel leveraging project funded by Abbvie. The project looks at the fundamentals of DEM simulations for single particle compacts. A paper was submitted to the Journal of Solids and Structures and is under review. The material presented here is directly from that paper that has not been published yet.
• A detailed study was conducted on the contact problem between dissimilar spheres (different radii and different materials cases). This problem is central in the cases of powder mixture compaction. Some results are presented in the report. A paper is being prepared for submission.
• An experimental study was conducted in the NaCl-Starch system – a binary system with peculiar behavior in terms of the strength of mixtures. Literature results that showed decreased strength of mixtures compared with the individual constituents have been duplicated. Ball milling of the mixture before compaction resulted in unusual high strength and ductility. Results from this work are being analyzed. A paper is expected to be submitted by early 2015.
• An x-ray transparent die has been designed for experiments within an x-ray tomography machine. The die was designed to withstand 150MPa.

Ongoing work focuses on (a) the importance of the elastic unloading behavior in DEM which may be related to residual stresses present in mixtures. (b) the introduction of failure models in DEM, (c) understanding the difficulties associated with material properties selection in DEM – primarily related to friction coefficient(s).