Yoshiki Kawano

Crystal Plasticity Analysis of Change in Active Slip Systems of α-Phase of Ti-6Al-4V Alloy under Cyclic Loading

In this paper, we investigated changes in active slip systems of α-phase of Ti-6Al-4V alloy under a cyclic plastic loading using a crystal plasticity finite element method. In the analyses, a bicrystal model was employed, and the crystallographic orientations were set so as that prismatic or basal slip system was the primary slip system in each grain. The results showed that there was a mechanism where the basal slip systems could reach the stage of activation under the cyclic plastic loading even though the condition was that the prismatic slips initially operate. The reason for the activity changes was due to the changes in the incompatibility between the grains by the work hardening, and the effect of the incompatibility on activities of slip systems appeared even in the perpendicular arrangements of the grains to the loading direction.

Voronoi Dynamics Simulation of Development of Lamellar Microstructure in Sea Ice

Developments of sea ice polycrystals from the sea surface are simulated in two-dimensional approximation by combining numerical methods for crystal growth, salinity diffusion and flux of heat. An anisotropic growth of ice crystals from a number of nuclei and their mutual impingements are numerically reproduced by a simple and novel technique, named Voronoi dynamics. Discharge of salt from solidified region and salinity condensation at the solid-liquid interface are also taken into consideration. Diffusion process of salinity and heat flux are evaluated by solving equations for diffusion and heat conduction, and growth of ice crystals is affected by these two factors. Results show that a layer of granular grains is formed near the sea surface and columnar shaped grains develop below it. Brine regions are mainly formed along grain boundaries in the layer of granular grains. In the region of columnar shaped grains, brine regions exist not only along grain boundaries but also inside grains. Columnar shaped crystal grains consist of ice platelets growing in the vertical direction and brine layers between them. These microstructural features are in accordance with experimental observations.