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Seminars
Uncoupled Crystal Plasticity-Transient Hydrogen Diffusion Analysis
- Hold Date
- 2010-06-01 15:30〜2010-06-01 17:00
- Place
- Ito Campus Open Learning Plaza 1st floor Room 10
- Object person
- Speaker
- Reza Miresmaeili (Faculty of Engineering, Kyushu University)
summary :
Uncoupled analyses have been implemented, in which the code
Zebulon is used for crystal plasticity analyses including a
fully anisotropic elasticity tensor and an in-house finite
element code is written for the hydrogen advection diffusion
computations. After completion of the structural analysis, the
diffusion code utilizing a Mass-Conservative Characteristic
Finite Element (MCC FE) scheme is programmed. The required
structural parameters - displacements, hydrostatic stresses
and equivalent plastic strains - are transferred step by step
from the previously completed structural analysis to the
hydrogen code.
properties for grain boundaries, which is usually the case in
research on grain boundary engineering, the non-homogeneous
stress field itself results in either depletion or enrichment
of hydrogen, depending on the direction of stress driven flux
produced by grain misorientation during straining. The
segregation of hydrogen is observed mainly at the grain
boundaries and some hydrogen perturbations appear. Results
show that the grain size has a significant effect not only on
the amount of hydrogen perturbation but also on the span of
region under perturbation. A decrease in the grain size by a
factor of 1.5 times induces an increase in maximum NILS
concentration by a factor of 1.76. Results of similar analyses
indicate that an increase in maximum NILS concentration occurs
by a factor of 3.13 in the case of a decrease in the grain
size by a factor of 2. Moreover, the effect of crystallographic orientations on the
hydrogen redistributions has been investigated. Different
hydrogen redistributions have evolved from the uniform initial
concentration due to dissimilar hydrogen fluxes resulted from
different crystallographic orientations. The contour of trap
site concentration changes due to variations in the contour of
equivalent plastic strain at different crystallographic
orientations. Progress has been made in that a one-way
coupled crystal plasticity-transient hydrogen diffusion
analysis is employed to solve a boundary value problem of an
elasto-plastic deformation in meso-scale. The hydrogen
distributions all over the polycrystal, including the hydrogen
concentration within the grains and close to the grain
boundaries, are determined. The results of this work may be
useful for controlling and optimizing the material
microstructure, eventually providing safe and reliable
hydrogen transport and storage systems.