Molecular dynamics simulations of nanopillar compression
Voimanen, Eerik (2023)
Voimanen, Eerik
2023
Teknis-luonnontieteellinen DI-ohjelma - Master's Programme in Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2023-01-27
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202301161442
https://urn.fi/URN:NBN:fi:tuni-202301161442
Tiivistelmä
Crystal plasticity experiments consider fundamental physics of complex systems. With simulations, statistical analysis is performed on nanopillar compression. With the statistical data this thesis has done research for better understanding of the structure to yield stress relation.
This thesis considers tantalum polycrystal nanopillar compression with two datasets. First of the two datasets considers 20 nm midway diameter Ta nanopillars with different grain sizes and indenter velocities. From the research done with the first dataset, there seems to be two regimes for the yield stress dependency on the grain size. For the average grain size larger than roughly 35 nm there seems to be a high dependency on the yield stress if the grain size is modified. If the grain size is increased, the yield stress increases, approaching the monocrystal yield stress. For grain sizes smaller than that, there seems to be almost no effect on the yield stress when it comes to modifying the grain size.
With statistical analysis on another dataset, which considers 20 nm to 50 nm midway diameter Ta nanopillars, it is also proven that statistical analysis is necessary to draw reliable conclusions. This is proven by a fact that a similar study, with some differences, but still more than enough in common with this research, has different conclusions with single samples than with this study has with a statistical analysis.
This thesis considers tantalum polycrystal nanopillar compression with two datasets. First of the two datasets considers 20 nm midway diameter Ta nanopillars with different grain sizes and indenter velocities. From the research done with the first dataset, there seems to be two regimes for the yield stress dependency on the grain size. For the average grain size larger than roughly 35 nm there seems to be a high dependency on the yield stress if the grain size is modified. If the grain size is increased, the yield stress increases, approaching the monocrystal yield stress. For grain sizes smaller than that, there seems to be almost no effect on the yield stress when it comes to modifying the grain size.
With statistical analysis on another dataset, which considers 20 nm to 50 nm midway diameter Ta nanopillars, it is also proven that statistical analysis is necessary to draw reliable conclusions. This is proven by a fact that a similar study, with some differences, but still more than enough in common with this research, has different conclusions with single samples than with this study has with a statistical analysis.