General Poster Session: Mechanics & Structural Reliability
Program Organizers: TMS Administration
Monday 5:30 PM
February 24, 2020
Room: Sails Pavilion
Location: San Diego Convention Ctr
G-31: Grain Boundaries Energy Measurements in Bicrystals and Polycrystals of Uranium Dioxide: Amani Ksibi1; 1Cea Cadarache
Grain boundaries (GBs) govern the properties of UO2 ceramics pellets used as nuclear fuels and thus determine their performances in reactor. Under irradiation, the fuel is subjected to an intergranular decohesion at the GBs due to the thermomechanical stresses induced by the temperature gradient and to the accumulation of fission gas bubbles. Improving the fuel performances requires a better knowledge of GBs in UO2 and of their fundamental properties including formation energies. For that purpose, GB energies (ƔGB) were measured, using the thermal grooving method, on polycrystalline samples and on bicrystals with a controlled geometry. For a given GB, similar ƔGB values were found on both materials, suggesting that bicrystals could be used as a model system to better understand the more complex polycrystalline materials. In parallel, ƔGB of similar GBs were simulated at the atomic scale with molecular dynamics. Calculated and experimental values were found in very good agreement.
G-32: On the Computational Solution of Continuum Dislocation Dynamics: A Comparison of Two Stress Update Algorithms: Peng Lin1; Ben Anglin2; Clint Geller2; Anter El-Azab1; Vignesh Vivekanandan1; 1Purdue University; 2Naval Nuclear Laboratory
An important step in continuum dislocation dynamics (CDD) is to determine the internal stress field of the current dislocation structure to compute the driving force for dislocations. This can be done by solving the stress equilibrium equation with an eigenstrain computed by time integration of Orowan’s law. In a staggered scheme of solving the CDD and crystal mechanics, we find that numerical errors accumulate and that the eigenstrain isn't consistent with the current dislocation field after some time. Here, we present an alternative way to update the eigenstrain by employing field dislocation mechanics approach where the eigenstrain is calculated directly from the incompatibility of the current dislocation field. These two different schemes for eigenstrain/stress update are compared and the results show that the error can be reduced by using field dislocation mechanics. The improved scheme has been used to predict the stress-strain behavior and dislocation microstructure in Cu crystals.