| Shohei Ueki | Last modified date：2024.04.19 |
Assistant Professor /
Strength of Materials
Department of Mechanical Engineering
Faculty of Engineering
Department of Mechanical Engineering
Faculty of Engineering
Graduate School
Undergraduate School
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Homepage
https://kyushu-u.elsevierpure.com/en/persons/shohei-ueki
Reseacher Profiling Tool Kyushu University Pure
Phone
092-802-3280
Academic Degree
Dr. Eng.
Country of degree conferring institution (Overseas)
No
Field of Specialization
Mechanical Properties of Materials
Total Priod of education and research career in the foreign country
00years00months
Research
Research Interests
- Fatigue crack propagation in lath martensite steels
keyword : Hierarchical microstructure, Habit plane orientation, Carbon content
2019.04. - Size effects in tensile deformation of single crystalline pure titanium
keyword : Micro-mechanical test, Extension twin, Work hardening
2022.04. - Study on origin of mechanical properties of metallic materials using micro-mechanical tests
keyword : Tensile, Fatigue, Lath martensite steel, Metastable austenitic steel, Titanium alloy, Fe-based amorphous alloy, Meteoric iron, Hydrogen embrittlement
2015.04.
Papers
| 1. | Shohei Ueki, Yoji Mine, Yu-Lung Chiu, Paul Bowen, Kazuki Takashima, Effects of crystallographic orientation and lamellar configuration on fatigue crack propagation in single-colony structures of Ti–6Al–4V alloy: Alternating shear crack growth vs. damage accumulation crack propagation, Materials Science and Engineering A, https://doi.org/10.1016/j.msea.2023.145885, 890, 145885, 2024.01, In this study, the fatigue crack propagation mechanisms in lamellar colonies of Ti–6Al–4V alloy were examined using miniature compact-tension specimens with a single-colony structure at the crack tip. Fatigue tests were performed on colonies with different α-phase crystallographic orientations and lamellar configurations with respect to the notch plane and direction, followed by post-fatigue metallographic analysis. Crack propagation occurs by three main mechanisms: 1) alternating shear due to in-plane prismatic slip, 2) damage accumulation via dislocation–dislocation interaction due to out-of-plane slip, and 3) interlamellar decohesion due to damage accumulation via lamellar interphase boundary–dislocation interaction. The slope of da/dN vs. ΔK is higher for alternating shear crack growth than for damage accumulation crack propagation via dislocation–dislocation interaction. This is due to an incubation period before substantive crack extension in the latter case, which is dominated by degree of strain accommodation associated with the activated slip systems. When the lamellar interphase boundaries are nearly perpendicular to the loading axis, the crack growth rates drastically increase by interlamellar decohesion. This is attributed to the reduced incubation period due to slip incompatibility at the interphase boundary where numerous crack nuclei were formed during damage accumulation process..  |
| 2. | Shohei Ueki, Yoji Mine, Kazuki Takashima, Microstructure-sensitive fatigue crack growth in lath martensite of low carbon steel, Materials Science and Engineering A, 10.1016/j.msea.2019.138830, 773, 2020.01, The elementary process of microstructural fatigue crack growth in single-packet structures with different habit-plane orientations to the loading axis was examined using miniature compact-tension specimens to comprehend the intrinsic resistance to fatigue crack growth in lath martensite of low carbon steel. When the angle between the loading axis and the normal to the habit plane (φ) was within ~45°, the cracks propagated nearly parallel to the habit plane. In packets with their habit planes nearly perpendicular (φ > ~70°) to the notch direction, the crack grew across the laths because of damage accumulation through the activation of the out-of-plane slips, which increased the fatigue crack growth resistance. Post-fatigue-test electron microscopy revealed that the microstructural inhomogeneity of the low carbon steel enhanced the strain localisation in coarse laths, which probably led to the premature fatigue crack growth. When the crack grew perpendicular to the habit plane, the intrinsic resistance to fatigue crack growth was higher in the fine-lath region than in the coarse-lath region.. |
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