Date(s) - 10/15/2020
2:00 pm - 3:00 pm
The Student Structural Seminar will be held Thursday, October 15th at 2:00pm via Zoom.
Charlyne Smith and Anne Marie Tan will be giving tutorial level presentations of their research. Abstracts for each presentation are presented below.
This month marks the first meeting of Structural Seminar for the fall semester! The presenter slots for our November 19th and December 17th meetings are also now filled. If you want to present (or volunteer one of your students to present) for the spring semester, tentative dates will be announced soon, and you can go ahead email me at firstname.lastname@example.org, to get a spot.
To find out more and join the discussion, add yourself to the Microsoft Teams group at the following link:
Join the Structural Seminar Teams Group
An investigation of the degree of fission gas pore interconnectivity in irradiated U-Mo fuels: an indicator of dimensional instability
Low enriched uranium-molybdenum (U-Mo) fuel is being investigated as a replacement for high enriched uranium fuels in high-performance research and test reactors to minimize proliferation of nuclear materials. The behavior of U-Mo fuels in reactor environments is informed by the microstructural evolution of the fuel, which dictates its performance and lifetime in the reactor. The formation, growth and interconnection of fission gas pores contributes to the release of fission gases from the fuel meat to the fuel cladding resulting in swelling, delamination, pillowing and potential failure. This work developed and tested a tool that investigates the degree of the interconnectivity of fission gas pores irradiated U-Mo fuels. The calculated fission gas pore interconnectivity was found to be positively correlated to the fission density as well as the fission gas pore morphology. The results showed that the rate of increase of the porosity with fission density is almost 4× the rate of fission gas pore interconnectivity at the fission densities studied (~4-6x1021fissions/cm3). This evidence reveals that as the fission gas pores form and grow, they do not become interconnected immediately. These findings can help inform computational models to predict fuel behavior in reactor environments.
Computation and application of the lattice Green function to dislocation structures in Ni-based superalloy
Dislocations are fundamental crystallographic defects that play key roles in determining the mechanical properties of structural materials. While the far-field geometry of a dislocation can be described by anisotropic continuum elasticity theory, the elastic solution diverges close to the dislocation core, requiring methods such as density functional theory (DFT) to accurately resolve the dislocation core geometry. However, the long-range strain field of a dislocation is incompatible with periodic boundary conditions, making it challenging to perform DFT calculations of isolated dislocations. The flexible boundary condition (FBC) approach captures the correct long-range response of the dislocation by coupling the dislocation core to an infinite harmonic bulk through the lattice Green function (LGF). We develop a numerical method to compute the LGF specifically for a dislocation geometry by directly accounting for its topology, which improves the accuracy and efficiency of the FBC approach. We apply this approach to compute the equilibrium core structures of dislocations in Ni and Ni3Al, demonstrating the first fully atomistic DFT calculation of an extended dislocation core structure in an intermetallic. Comparisons between our predicted dissociation distances and those estimated from continuum models demonstrate the limitations of such models and highlights the need for accurate atomistic calculations.