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Journal Articles

Improving fatigue performance of laser-welded 2024-T3 aluminum alloy using dry laser peening

Sano, Tomokazu*; Eimura, Takayuki*; Hirose, Akio*; Kawahito, Yosuke*; Katayama, Seiji*; Arakawa, Kazuto*; Masaki, Kiyotaka*; Shiro, Ayumi*; Shobu, Takahisa; Sano, Yuji*

Metals, 9(11), p.1192_1 - 1192_13, 2019/11

 Times Cited Count:2 Percentile:64.55(Materials Science, Multidisciplinary)

The purpose of the present study was to verify the effectiveness of dry laser peening (DryLP), which is the peening technique without a sacrificial overlay under atmospheric conditions using femtosecond laser pulses on the mechanical properties such as hardness, residual stress, and fatigue performance. After DryLP treatment of the laser-welded 2024 aluminum alloy, the softened weld metal recovered to the original hardness of base metal, while residual tensile stress in the weld metal and heat-affected zone changed to compressive stresses. The fatigue life almost doubled at a stress amplitude of 180 MPa and increased by a factor of more than 50 at 120 MPa. As a result, DryLP was found to be more effective for improving the fatigue performance of laser-welded aluminum specimens with welding defects at lower stress amplitudes.

Journal Articles

Study of catalytic reaction at electrode-electrolyte interfaces by a CV-XAFS method

Kusano, Shogo*; Matsumura, Daiju; Asazawa, Koichiro*; Kishi, Hirofumi*; Sakamoto, Tomokazu*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Mizuki, Junichiro*

Journal of Electronic Materials, 46(6), p.3634 - 3638, 2017/06

 Times Cited Count:1 Percentile:88.36(Engineering, Electrical & Electronic)

Journal Articles

Formation of amorphous graded structure in Bi$$_{3}$$Pb$$_{7}$$ intermetallic compounds under strong gravitational field

Mashimo, Tsutomu; Iguchi, Yusuke*; Bagum, R.*; Sano, Tomokazu*; Takeda, Shingo*; Kimura, Shigeru*; Sakata, Osami*; Ono, Masao; Okayasu, Satoru; Tsurui, Takao*; et al.

Defect and Diffusion Forum, 289-292, p.357 - 360, 2009/04

A visible four-layers structure with anomalous nano-sturucture was formed from a homogeneous e-phase Bi$$_{3}$$Pb$$_{7}$$ intermetallic compound under a strong gravitational field (1.02$$times$$10$$^{6}$$ G, 130$$^{circ}$$C, 100 hours). In the 4th layer (lowest-gravity region), pure Bi particles precipitate. In the 2nd 3rd layers, composition graded structures, where Pb content increased along the gravity direction, were formed. It was found that the very broad XRD peak appeared in the 2nd layer, which indicated that an amorphous structure was contained.

Journal Articles

Formation of multi-layer structures in Bi$$_{3}$$Pb$$_{7}$$ intermetallic compounds under an ultra-high gravitational field

Mashimo, Tsutomu; Iguchi, Yusuke*; Bagum, R.*; Sano, Tomokazu*; Sakata, Osami*; Ono, Masao; Okayasu, Satoru

AIP Conference Proceedings 973, p.502 - 505, 2008/03

Ultra-high gravitational field (Mega-gravity field) can realize the sedimentation of atoms (diffusion) even in solids, and is expected to form a composition-graded structure and/or nonequilibrium phase in multi-component condensed matter. We had realized the sedimentation of substitutional solute atoms in miscible systems (Bi-Sb, In-Pb, etc.). In this study, the mega-gravity experiment at high temperature was performed on a thin-plate sample (0.7 mm in thickness) of intermetallic compound Bi$$_{3}$$Pb$$_{7}$$. A visible four-layers structure appeared, which indicated different microscopic structures. In the lowest-gravity region layer, Bi phase appeared. In the mid layers, the composition-graded structure was formed, while the powder X-ray diffraction patterns show difference. Such multi-layers structure was expected to show unique physical properties such as superconductivity. Keywords: Sedimentation of atoms, Ultra-high gravity field, Bi$$_{3}$$Pb$$_{7}$$, Graded structure.

Journal Articles

Incorporating Tritiated Water into a $$^{14}$$C-Sampling System for Quantitative Estimation of$$^{14}$$C Activity in Airborne Effluent

Koarashi, Jun; Akiyama, Kiyomitsu; Asano, Tomohiro; Yokota, Tomokazu*

Journal of Radioanalytical and Nuclear Chemistry, 262(3), p.771 - 774, 2005/01

Effect of incorporating tritiated water into a $$^{14}$$C sampling system on sample preparation and $$^{14}$$C activity measurement by liquid scintillation counting were investigated. Experiments derived the limit of water content in prepared sample, and also demonstrated that $$^{14}$$C activity can be determined without any interference from$$^{3}$$H contamination for clear-solution sample. The results enabled us to estimate permissible reelative humidity of air required for accomplishing sample preparation and $$^{14}$$C activity measurement. These showed that for sampling of air with less than the permissible relative humidity, total $$^{14}$$C activity in airborne effluent can be evaluated accurately with no dehumidification of air.

JAEA Reports

Methods and Their Performances for Collecting Tritium, Carbon-14 and Radioiodine in Airborne Effluent from Tokai Reprocessing Plant

Koarashi, Jun; Kozawa, Tomoyasu*; Yokota, Tomokazu*; Isaka, Keisuke*; Akiyama, Kiyomitsu; Asano, Tomohiro

JNC-TN8410 2004-003, 49 Pages, 2004/07

JNC-TN8410-2004-003.pdf:1.45MB

Radioactive airborne effluent discharged from Tokai reprocessing plant (TRP) contains tritium, carbon-14 and radioiodine. These radionuclides are collected with appropriate methods, respectively, in stacks to monitor their concentrations and discharged amounts. This report describes (1) the methods for collecting these radionuclides in TRP; (2) evaluations of the concentrations and discharged amounts; and (3) investigations on estimating performances of the collecting methods. The investigations showed that the collecting methods used in TRP have collecting efficiencies of more than 90% for tritium and radioiodine, and almost 100% for carbon-14. Considerations concerning collection of radionuclides in airborne effluent, made in this study, provided some technical aspects required for establishing more reliable monitoring systems.

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