Type of Document Master's Thesis Author Yang, Yi Author's Email Address email@example.com URN etd-02172011-125639 Title Measurement of Spatial Variation of Density of Compacted Powder Using Synchrotron Microtomography Degree Master of Science in Civil Engineering (M.S.C.E.) Department Civil & Environmental Engineering Advisory Committee
Advisor Name Title Khalid, Alshibli Committee Chair Zhang,Guoping Committee Member Clinton, Willson Committee Member Keywords
- density variation
- compacted powder
- synchrotron microtomography
Date of Defense 2011-01-28 Availability unrestricted AbstractThis research considers density change in powder metallurgy when compacting a powder blend in a die. In order to provide insights into particle behavior during compaction, atomized aluminum powders with an average particle size of 100 Ám were used in two different compaction configurations. The compaction dies are cylindrical in shape: compaction configuration I displays an upper punch, a die, a lower punch, and a spacer. Compaction configuration II displays an upper punch, two dies, a lower punch, and a spacer with different geometry. The Synchrotron Microtomography scans were conducted on both compaction configurations. For compaction configuration I, the scan were acquired at axial strains of 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50%. The scans for compaction configuration II were acquired at axial strains of 0%, 3%, 6%, 9% and 12%.
After scanning these compacted powders, the images were analyzed by means of computer codes that were written using Interactive Data Language (IDL) program. Programs of density map and image segmentation were used to analyze the image. Then, the spatial density maps and histograms of density variation were developed. Based on this data, the study generated curves of row statistical density, column statistical density, and compaction response in order to understand density change in compacted powder.
This study revealed that Synchrotron Microtomography can be successfully applied to examine density variation and track microscopic deformations of aluminum powders under compaction. The density distribution within the compaction die was controlled by several factors, such as constitutive behavior of powder, friction interaction between powder and die wall, geometry of compaction die, and sample filling condition.
Springback represents an important factor for influencing density distribution, especially during the scanning process. Moreover, the effect of Springback cannot be eliminated and can only be decreased in powder compaction. The aluminum compacts exhibit considerable side-to-side asymmetry which agrees with previous research findings. Finally, the generation of void gap between layers indicates the inefficiency in transmitting forces during compaction.
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