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論文

Study on $$^{rm 99m}$$Tc separation/concentration technology from $$^{99}$$Mo by (n,$$gamma$$) method, 4

末松 久幸*; Yang, Y.*; 伊藤 陽登*; Le, A. V.*; Su, Y.*; 加藤 涼那*; Do, T. M. D.*; 鈴木 達也*; 大沢 直樹*; 藤田 善貴; et al.

KURNS Progress Report 2025, P. 118, 2026/06

https://adm.rri.kyoto-u.ac.jp/pub/progressrep2/

これまでの研究で、中性子照射した$$beta$$-MoO$$_{3}$$ターゲットからホットアトムの反跳効果により水中への$$^{99}$$Mo抽出率が時間とともに増加することを示した。本研究では、水抽出後ターゲットを再照射するためのリサイクル性評価を目的に、水浸漬後の$$beta$$-MoO$$_{3}$$粉末を乾燥した試料の$$^{99}$$Mo生成量及び構造安定性を確認した。また、比較試料として、$$beta$$-MoO$$_{3}$$、MoO$$_{2}$$、Mo$$_{4}$$O$$_{11}$$及び水浸漬させた水和$$beta$$-MoO$$_{3}$$を用意した。これらの試料を京都大学研究用原子炉(KUR)で20分間照射後、粉末を蒸留水中において室温で5.5時間攪拌させ、水への$$^{99}$$Mo抽出率を調べた。その結果、乾燥後の$$beta$$-MoO$$_{3}$$が最も高い抽出率を示し、対照的に水和$$beta$$-MoO$$_{3}$$は通常の$$beta$$-MoO$$_{3}$$相と比較して抽出率が著しく低下した。また、MoO$$_{2}$$の抽出率は低く、Mo$$_{4}$$O$$_{11}$$ではほとんど$$^{99}$$Moが抽出されなかった。これらの結果から、ホットアトムによる反跳効果及び水への$$^{99}$$Mo抽出率がモリブデン酸化物の結晶構造及び酸化状態に依存することを明らかにした。

論文

Plastic deformation and microstructural evolution during cryogenic charpy impact of high-Mn austenitic steel

Jiang, L.*; Wang, H. H.*; Su, Y. H.; 徐 平光; 篠原 武尚; Xia, B.*; Wang, Y. W.*

Journal of Materials Science, 61(14), p.9754 - 9775, 2026/04

https://doi.org/10.1007/s10853-026-12472-x
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

In this study, pulsed neutron Bragg-edge transmission imaging was employed to characterize plastic deformation of high-manganese austenitic steel during cryogenic impact fracture. Electron backscatter diffraction was used to examine the microstructural evolution. The results reveal that the Bragg-edge width was identified as the critical value for large plastic deformation. Both crack initiation and stable crack growth regions exhibited higher levels of plastic deformation, twin density, and dislocation density compared to unstable crack growth regions. As the test temperature decreased from 273 K to 77 K, the transition point from stable to unstable crack growth occurred earlier. This is responsible for the reduction in impact absorbed energy. These findings provide new insights into the cryogenic toughening mechanism of high-manganese steel.

論文

New insights into the cryogenic fracture mechanism of high-Mn austenitic steels using interrupted Charpy impact tests

Xia, B.*; Wang, H. H.*; Su, Y. H.; 徐 平光; 篠原 武尚; Wang, Y. W.*

Materials Science & Engineering A, 957, p.149940_1 - 149940_7, 2026/04

https://doi.org/10.1016/j.msea.2026.149940
 被引用回数：1 パーセンタイル：76.28(Nanoscience & Nanotechnology)

The cryogenic fracture mechanism of high-Mn austenitic steels was investigated using a quasi-in situ experiment of interrupted Charpy impact test, together with electron backscatter diffraction and neutron Bragg-edge transmission imaging. The results show that voids coalesce through void sheeting at 77 K, a fracture mechanism associated with superior cryogenic toughness. The widely and ring-like distributed deformation twins ahead of the crack tip contribute limitedly to alleviating strain localization at 77 K. However, by suppressing the increase in stress triaxiality, deformation twins play a key role in promoting void sheeting and preventing the transition to quasi-cleavage fracture. This work lays the foundation for subsequent investigations into cryogenic toughening.

論文

Magnetic evolution, phase transitions, and electronic band structure of the ferrotoroidic candidate Ba$$_6$$Cr$$_2$$S$$_{10}$$

Zhao, G.*; Li, J.*; Zhang, J.*; 小嶋 健児*; Cai, Y.*; 伊藤 孝; Yoon, S. W.*; Wang, X.*; 前川 禎通*; Su, G.*; et al.

Physical Review Research (Internet), 8(1), p.013331_1 - 013331_10, 2026/03

https://doi.org/10.1103/h576-nnnz

Ferrotoroidic materials, which break both time- and space-reversal symmetries to enhance magnetoelectric responses, are of great interest for applications. Ba$$_6$$Cr$$_2$$S$$_{10}$$, a recently synthesized quasi-one-dimensional ferrotoroidic candidate, combines polarization, magnetization, and toroidal moment, yet its electronic band structure, magnetic evolution, and phase transitions remain incompletely understood to date. Here, we investigate Ba$$_6$$Cr$$_2$$S$$_{10}$$, using electrical transport, direct current magnetization, alternating current susceptibility, specific heat, and muon spin rotation ($$mu$$SR) measurements, along with various first-principles calculations. Electrical transport measurements and density functional theory confirm a narrow band gap ($$sim$$0.707~eV, experimentally; $$sim$$0.680~eV, theoretically). $$mu$$SR measurements reveal that static magnetism dominates down to 2~K, with an ordered volume fraction of $$sim$$89% at this temperature. Two distinct transitions are identified: one around the N$'{e}$el temperature [$$T_{rm N}=(8pm 1)$$~K] and another corresponding to a phase transition near 30~K, as consistently indicated by our complementary experimental techniques. The absence of dynamic critical behaviors and the lack of a $$lambda$$-type specific heat anomaly are consistent with a first-order-like transition at $$T_{rm N}$$. Based on various complementary experimental results and theoretical calculations, we propose a hypothesis that the $$sim$$30~K broad feature arises from the complex interplay between crystal structure distortion and magnetic coupling, which is potentially directly linked to ferrotoroidicity. As the first study integrating $$mu$$SR with complementary experiments and first-principles calculations to explore ferrotoroidicity, this work provides key insights into the underlying physics of Ba$$_6$$Cr$$_2$$S$$_{10}$$ and related compounds in this area.

論文

Residual stress relief effect in gradient structural steel and remaining life evaluation under stochastic fatigue loads

Qin, T. Y.*; Hu, F. F.*; 徐 平光; Zhang, R.*; Su, Y. H.; Ao, N.*; Li, Z. W.*; 篠原 武尚; 菖蒲 敬久; Wu, S. C.*

International Journal of Fatigue, 202, p.109233_1 - 109233_16, 2026/01

https://doi.org/10.1016/j.ijfatigue.2025.109233
 被引用回数：7 パーセンタイル：69.50(Engineering, Mechanical)

The surface induction-hardened S38C medium carbon steel shows a good balance of strength and toughness, but complicates the evaluation of fatigue resistance, mainly because of gradient residual stress (RS) and grains. An integrated fatigue resistance assessment (AIFA) framework was proposed to consider the residual stress relief under stochastic loads. To this end, quasi-in situ neutron diffraction and Bragg-edge imaging were combined to probe the evolution of residual stress during crack propagation. Firstly, a rigid-flexible coupled vehicle dynamics model was adopted to obtain the time-domain variable amplitude loading spectrum. Then, Fortran subroutines were developed to assign these data into full-scale S38C axle model, and the remaining life was predicted using the damage tolerance approach. The results demonstrate that crack propagation would accelerate when residual stress is considered in the case of the crack depth exceeding 3.0 mm. It is, for the first time, found that 15 mm- and 5 mm-thickness fan-shaped specimens can retain the axial and hoop residual strain in terms of diffraction angle variation, respectively, for full-scale structural S38C steel axles. In the absence of RS, the remaining life of the axle decreases sharply from 624,800 to 51,300 km as the crack depth increases from 3.0 to 16 mm. Compared with the standard method under constant amplitude loading without residual stress relief, the present AIFA method provides the more accurate but conservative fatigue life prediction.

論文

Integrated neutron and surface-based characterization of stress/strain fields and microstructural evolution during fatigue crack growth in SUS304 stainless steel

Su, Y. H.; 篠原 武尚; Parker, J. D.*; 及川 健一; 甲斐 哲也; Gong, W.; 伊東 達矢; Harjo, S.; 相澤 一也; 鬼柳 善明*; et al.

Materials Science & Engineering A, 951, p.149607_1 - 149607_16, 2026/01

https://doi.org/10.1016/j.msea.2025.149607
 被引用回数：0 パーセンタイル：0.00(Nanoscience & Nanotechnology)

Local variations in residual stress/strain and microstructure during fatigue crack growth in compact tension specimens of SUS304 austenitic stainless steel were investigated using complementary methods: pulsed neutron Bragg-edge imaging (NBEI), neutron diffraction (ND), digital image correlation (DIC) and electron backscatter diffraction (EBSD). Surface strain fields were evaluated using DIC and EBSD. NBEI provided two-dimensional averaged microstructure information, whereas ND yielded detailed three-dimensional distributions of residual lattice (elastic) strain and stress. This study particularly focused on how NBEI is helpful in understanding overall damage characteristics in the vicinity of a crack tip two-dimensionally. Distribution of microstructural parameters associated with crack growth, such as lattice constant, crystallite size, and texture, across the entire specimen was considered using Bragg-edge spectral analysis. The plastic zone in front of the crack tip, characterized by reduced crystallite size, was observed during crack propagation. After final fracture, two distinct zones with reduced crystallite size were identified: one caused by localized plastic deformation near the crack tip, and the other by bending at the back end of the specimen. This paper introduces the four experimental techniques and describes their respective features. Each method has its own advantages and limitations; However, by integrating their results, a more comprehensive understanding of the overall stress/strain field can be achieved.

論文

Lyotropic polymer liquid crystal coating; Enabling lamellar ion-conduction pathways for superior C-Rate performance in NCM523 cathodes

Marium, M.*; 青木 健太郎*; He, Y.*; 山本 勝宏*; Suwansoontorn, A.*; 生田 聖也*; 原 光生*; 永野 修作*; 長尾 祐樹*; 西川 慶*; et al.

ACS Applied Energy Materials (Internet), 8(22), p.16589 - 16600, 2025/11

https://doi.org/10.1021/acsaem.5c02323
 被引用回数：1 パーセンタイル：20.13(Chemistry, Physical)

High C-rate capability and energy-density stability are crucial for advanced lithium-ion batteries (LIBs). However, these two characteristics typically conflict in conventional systems. Herein, a lyotropic polymer liquid crystal (LPLC)-based coating was applied to the surface of LiNi$$_{0.5}$$Co$$_{0.2}$$Mn$$_{0.3}$$O$$_{2}$$ (NCM523) cathode to construct a highly ion-conductive artificial cathode electrolyte interface (CEI) layer, aiming to supersede traditional CEIs for LIBs. The coating material, composed of an amphiphilic lithium-substituted alkyl-sulfonated polyimide (ASPI-Li) and an appropriate amount of organic liquid electrolyte, forms nanoscale ion conduction channels that act as an artificial CEI layer, providing enhanced local Li-ion activity at the NCM523 surface. The ion-conduction channels, regulated by the layered structure within the ASPI-Li coating layer, significantly accelerated ion-diffusion kinetics at the electrode/electrolyte interface, thereby delivering superior C-rate capability at ambient temperatures compared with conventional LIB systems. This work, guided by molecular design, provides insights into the development of next-generation artificial CEI layers for efficient and sustainable energy-storage systems.

論文

Study on $$^{rm 99m}$$Tc separation/concentration technology from $$^{99}$$Mo by (n,$$gamma$$) method, 3

末松 久幸*; Yang, Y.*; 北川 大凱*; Do, T. M. D.*; 鈴木 達也*; 藤田 善貴; 藤原 靖幸*; 吉永 尚生*; 堀 順一*

KURNS Progress Report 2024, P. 123, 2025/06

本研究では、中性子照射により$$^{99}$$Moを生成し、水中へ抽出するためのターゲット材としての$$beta$$-MoO$$_{3}$$粒子の有効性を評価した。これまでの研究では$$beta$$-MoO$$_{3}$$ウィスカーを使用していたが、抽出率が高い理由が結晶構造によるものなのかウィスカー形状による短い拡散距離のためなのかが明確でなかった。また、ターゲット中に$$alpha$$-MoO$$_{3}$$が混在しており、純粋な$$beta$$-MoO$$_{3}$$の特性を評価できていなかった。そこで本研究では、熱蒸発法と金属フィルターを組み合わせることで、大きな$$alpha$$-MoO$$_{3}$$結晶を除去し、純度の高い微細な$$beta$$-MoO$$_{3}$$粒子を得ることに成功した。得られた粒子は約130nmの平均粒径を持ち、中性子照射に用いた。照射後、粒子を水中に分散し、定期的に固体と溶液を分離して$$^{99}$$Moの放射能を測定した結果、室温条件においても生成した$$^{99}$$Moの約75%が水中へ抽出されることが確認された。これは、$$beta$$-MoO$$_{3}$$の結晶構造特性が$$^{99}$$Mo抽出に有利に働いている可能性を示唆している。以上の結果から、$$beta$$-MoO$$_{3}$$粒子は、$$^{99}$$Moの生成および水中抽出の双方で優れた特性を示すターゲット材料として有望であると結論づけられた。

論文

Temperature and time dependence on extraction of Molybdenum-99 hot atoms from neutron-irradiated $$beta$$-molybdenum trioxide particles into water

Yang, Y.*; Ngo, M. C.*; 北川 大凱*; 藤田 善貴; 高橋 由紀子*; 鈴木 達也*; 中山 忠親*; Do, T. M. D.*; 新原 晧一*; 末松 久幸*

RSC Advances (Internet), 15(22), p.17222 - 17229, 2025/05

https://doi.org/10.1039/D5RA01952D
 被引用回数：1 パーセンタイル：21.18(Chemistry, Multidisciplinary)

本研究は、温度及び加熱時間が$$^{99}$$Moの水への抽出に及ぼす影響を調査したものである。$$beta$$-MoO$$_{3}$$粒子は熱蒸発により合成後、X線回折及び透過型電子顕微鏡を用いて特性評価した。これらを京都大学研究用原子炉によって中性子照射し、照射した$$beta$$-MoO$$_{3}$$粒子を、20$$sim$$50$$^{circ}$$Cの水中にそれぞれ1$$sim$$5.5時間分散させることで$$^{99}$$Moを抽出した。照射後の$$^{99}$$Moの放射能及び抽出した$$beta$$-MoO$$_{3}$$溶液中の$$^{99}$$Moの放射能は高純度ゲルマニウム半導体検出器によって測定した。その結果、水温の上昇と加熱時間の増加により、$$^{99}$$Moの抽出効率は20.31$$pm$$1.24%から66.88$$pm$$1.42%へ向上した。この抽出プロセスの活性化エネルギーは、結晶性MoO$$_{3}$$中の単純な原子拡散の活性化エネルギーよりも低く、水和MoO$$_{3}$$相の形成またはプロトン伝導の活性化エネルギーと同程度か、より高いことを明らかにした。この結果は、水和MoO$$_{3}$$相が$$^{99}$$Moの抽出を加速したことを示唆している。本研究は$$^{99}$$Moホットアトムの抽出における温度と時間依存性を初めて調査したものであり、放射性医薬品である$$^{99}$$Mo/$$^{99m}$$Tcの大規模生産に向けた有望な手法を提供する。

論文

Residual stress relaxation of railway gradient S38C steel during fatigue crack growth by neutron imaging and diffraction

Hu, F. F.*; Qin, T. Y.*; Su, Y. H.; He, L. H.*; Ao, N.*; Parker, J. D.*; 篠原 武尚; Wu, S. C.*

International Journal of Fatigue, 193, p.108826_1 - 108826_14, 2025/04

https://doi.org/10.1016/j.ijfatigue.2025.108826
 被引用回数：7 パーセンタイル：76.61(Engineering, Mechanical)

The relaxation behaviors of residual stress and the influence on the fatigue resistance of S38C axles with induction hardening were investigated by using advanced Bragg-edge transmission imaging and neutron diffraction as well as XFEM-based numerical modeling. The Bragg-edge imaging results indicate that lattice parameters change as the crack develops, which then leads to a decrease of residual strain. In addition, it was observed from neutron diffraction results that all three residual stress components decrease with the crack growth. By contrast, the compressive residual stress in the axle surface was almost fully released when the crack propagated to the matrix material zone. Furthermore, residual stress relaxation was validated by the extended finite element method. These new insights confirm stress relaxation in railway S38C axles during crack propagation, which must be considered while carrying out the structural integrity assessment.

論文

Residual stress measurement and lifetime evaluation of railway axles by neutron scattering technology

Hu, F.-F.*; Qin, T.-Y.*; Ao, N.*; 徐 平光; Su, Y. H.; Parker, J. D.*; 篠原 武尚; 菖蒲 敬久; Kang, G.-Z.*; Ren, M.-M.*; et al.

Journal of Traffic and Transportation Engineering, 25(2), p.75 - 93, 2025/04

https://dx.doi.org/10.19818/j.cnki.1671-1637.2025.02.005
https://transport.chd.edu.cn/en/article/doi/10.19818/j.cnki.1671-1637.2025.02.005
https://transport.chd.edu.cn/cn/article/doi/10.19818/j.cnki.1671-1637.2025.02.005

To accurately predict the remaining lifetime of surface-strengthened railway axles, a damage tolerance method considering three-dimensional (3D) residual stresses was proposed. By taking the induction-hardened carbon steel S38C axle as an example, two-dimensional (2D) distribution characterization of residual strain and 3D residual stress measurement were performed through comprehensive application of the neutron Bragg-edge transmission imaging and angle-dispersive neutron diffraction experiments. A numerical method was employed to implant the 3D residual stress into the axle model, and the remaining lifetime of the full-scale axle was studied by coupling the measured load spectrum, press-fit loads, and residual stresses. Experimental results shows that, both axial and hoop directions present a compressive residual strain gradient layer of about 3 mm, with a maximum compressive residual strain of up to -4500 $$mu$$$$varepsilon$$ in the surface layer, yet a maximum tensile strain of up to 1000 $$mu$$$$varepsilon$$ in the core. The maximum axial and hoop compressive stresses of the axle are about -500 MPa and -303 MPa respectively, while radial stresses overall fluctuate in the zero mean stress range. At depths beyond 4.5 mm from the surface layer, all three components are tensile stresses. The axle surface layer is subjected to compressive residual stresses, and crack propagation does not occur if the crack depth is less than 4.5 mm. Nevertheless, cracks propagate accelerates when the crack depth is greater than 4.5 mm. Different crack propagation depth thresholds lead to a larger calculated remaining lifetime for the residual stress-free condition than for the case where 3D residual stresses are taken into account. However, the axle remaining service mileage of the axle of 227000 Km under the most conservative conditions exceeds 3.5 non-destructive inspection (NDI) cycles, with a large safety margin. The experimental results can provide a scientific reference for the development and optimization of NDI cycles for surface-strengthened railway axles.

論文

Robustness of ferromagnetism in van der Waals magnet Fe$$_3$$GeTe$$_2$$ to hydrostatic pressure

Wang, Y.*; Zeng, X.-T.*; Li, B.*; Su, C.*; 服部 高典; Sheng, X.-L.*; Jin, W.*

Chinese Physics B, 34(4), p.046203_1 - 046203_6, 2025/03

https://doi.org/10.1088/1674-1056/adb26f
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

二次元ファンデルワールス強磁性体Fe$$_3$$GeTe$$_2$$(FGT)は、その高いキュリー温度、容易な調整性、空気中での優れた構造安定性から、スピントロニクスデバイスへの応用に大きな可能性を秘めている。理論的研究により、外部パラメータとしての圧力が強磁性特性に大きく影響することが示されている。本研究では、5GPaまでの高圧中性子粉末回折(NPD)実験を行い、FGTの静水圧による構造及び磁気特性の変化を調べた。NPDデータは、静水圧による見かけ上の抑制にもかかわらず、FGTにおける強磁性の頑健性を明らかにした。圧力が0から5GPaまで増加すると、キュリー温度は225(5)Kから175(5)Kまで単調減少し、Feの秩序モーメントが劇的に抑制されることがわかった。圧力による構造相転移は5GPaまで観測されなかったが、結合長と結合角の変化を定量的に解析した結果、交換相互作用が大きく変化していることがわかった。

論文

Redifining RADEN's high-resolution neutron imaging capabilities

Sans-Planell, O.*; 篠原 武尚; Grazzi, F.*; Cantini, F.*; Su, Y. H.; 松本 吉弘*; Parker, J. D.*; Manke, I.*

Review of Scientific Instruments, 95(11), p.113702_1 - 113702_5, 2024/11

https://doi.org/10.1063/5.0235243
 被引用回数：2 パーセンタイル：10.09(Instruments & Instrumentation)

This study presents a significant development in the Energy-Resolved Neutron Imaging System RADEN, in the Japan Proton Accelerator Research Complex, Japan. Through a systematic study, the collimation power of the facility was reevaluated. To perform the calculation of the L/D factor of the beam, a state-of-the-art method has been used, along with a standard reference sample to measure the resolution of neutron images. To add robustness to the results, the study compares five different scintillators of different composition and thickness.

論文

強磁性5$$d$$ $$j_{eff}=3/2$$絶縁体Sr$$_3$$OsO$$_6$$のX線磁気円二色性測定

若林 勇希*; Krockenberger, Y.*; 山神 光平*; 和達 大樹*; 芝田 悟朗; 藤森 淳*; 河村 直己*; 鈴木 基寛*; 谷保 芳孝*; 山本 秀樹*

SPring-8/SACLA利用研究成果集(インターネット), 12(5), p.291 - 293, 2024/10

https://doi.org/10.18957/rr.12.5.291

本研究では、高温強磁性酸化物Sr$$_3$$OsO$$_6$$の電子状態を明らかにすることを目的として、Os $$L_{2,3}$$吸収端におけるX線吸収分光(XAS)及びX線磁気円二色性(XMCD)測定を行った。実験結果から、Osの軌道磁気モーメントがスピン磁気モーメントと同程度のオーダーであることが明らかになった。しかし、XMCD総和則による推定では、軌道磁気モーメントはSQUID磁化測定の値よりもかなり小さかった。今後の課題としては、SrやOの吸収端でのXMCD測定による磁気モーメントの観測や、サンプルの経時変化を低減させるための対策が挙げられる。

論文

Comparison between carrier transport property and crystal quality of TlBr semiconductors

渡辺 賢一*; 須貝 優介*; 長谷川 創大*; 田中 清志朗*; 人見 啓太朗*; 野上 光博*; 篠原 武尚; Su, Y. H.; Parker, J. D.*; Kockelmann, W.*

Scientific Reports (Internet), 14, p.25224_1 - 25224_13, 2024/10

https://doi.org/10.1038/s41598-024-76005-9
 被引用回数：2 パーセンタイル：10.09(Multidisciplinary Sciences)

Thallium bromide (TlBr) semiconductor detectors are being developed as promising candidates for high-detection-efficiency, high-energy-resolution, and room-temperature gamma-ray spectrometers. This study presents methods for evaluating TlBr crystal quality and carrier transport characteristics using neutron Bragg-dip imaging and the time-of-flight method for pulsed-laser-induced carriers, respectively. In this study, two samples obtained from both the upstream and downstream region in the crystal ingot were evaluated.

論文

Magnetic excitation in the hyperkagome antiferromagnet Mn$$_{3}$$RhSi

社本 真一; 山内 宏樹; 飯田 一樹*; 池内 和彦*; 金子 耕士; Chen, Y.-S.*; 矢野 真一郎*; Hsu, P.-T.*; Lee, M. K.*; Hall, A. E.*; et al.

Physical Review Research (Internet), 6(3), p.033303_1 - 033303_7, 2024/09

https://doi.org/10.1103/PhysRevResearch.6.033303

Mn$$_{3}$$RhSiの磁気励起は少なくとも0.3から140meVに広がる。200Kでの非弾性散乱強度を積分することで、Mnサイト当たり約5$$mu_{B}$$の磁気モーメントは、約5$$mu_{B}$$であることがわかった。一方で、長距離磁気秩序の磁気モーメントは4Kでわずか2.61$$mu_{B}$$であり、多くの部分が低温まで揺らいでいることがわかった。

論文

Application of neutron characterization techniques to metallic structural materials

Wang, Y.*; Gong, W.; Su, Y. H.; Li, B.*

Acta Metallurgica Sinica, 60(8), p.1001 - 1016, 2024/08

https://doi.org/10.11900/0412.1961.2024.00063
 被引用回数：6 パーセンタイル：51.20(Metallurgy & Metallurgical Engineering)

The correlation between the atomic structure, microstructure, and macroscopic properties of structural materials remains a core issue in materials research. In recent years, substantial progress has been achieved in constructing accelerator-based neutron sources and related experimental techniques, offering a robust platform for an in-depth understanding of the aforementioned correlation under real-time and in situ conditions. This article reviews the latest advancements in the application of major neutron characterization techniques, including neutron diffraction, Bragg-edge imaging, small-angle neutron scattering, pair distribution function analysis, and quasi-elastic/inelastic neutron scattering, in structural materials. Furthermore, it particularly highlights the origins and evolution of internal stresses during the phase transformations of steels, deformation mechanisms in light metals such as magnesium alloys, and microstructure and residual stress analyses using Bragg-edge imaging. Finally, a brief outlook on future development trends is provided.

論文

Gradient residual strain determination of surface impacted railway S38C axles by neutron Bragg-edge transmission imaging

Hu, F. F.*; Qin, T. Y.*; Ao, N.*; Su, Y. H.; Zhou, L.*; 徐 平光; Parker, J. D.*; 篠原 武尚; Chen, J.*; Wu, S. C.*

Engineering Fracture Mechanics, 306, p.110267_1 - 110267_18, 2024/08

https://doi.org/10.1016/j.engfracmech.2024.110267
 被引用回数：5 パーセンタイル：43.19(Mechanics)

Non-destructive and quantitative mapping of gradient residual strain distribution in surface-hardened railway S38C axles could provide a positive reference for determining service lifetime and maintenance strategy. To tackle this concern, time-of-flight neutron Bragg-edge transmission imaging was employed by real axle samples with and without impacted crater. A novel and simple procedure to formulate the residual strain field was also developed in this work, with the transmission batch code in Appendix A. By mapping the global two- dimensional residual strains, it can be verified that the residual strains into the axle are uniformly distributed in the hoop direction. Subsequently, it was revealed that the axial and hoop residual strains, respectively in the cylinder and the long strip samples prepared from a real S38C hollow axle, indicated a gradient evolution distribution with a depth of $$sim$$ 8 mm, covering a range of -5500 $$sim$$ 1000 $$mu$$$$varepsilon$$ for axial strains and -6500 $$sim$$ 1000 $$mu$$$$varepsilon$$ for hoop strains. More importantly, the maximum compressive lattice strain of the cylinder sample was increased by 15.61%, and 22.35% at the impacting speeds of 100, and 125 m/s, respectively; and that of the long strip sample increased by 29.17%, and 43.70%, respectively. It can thus be concluded that lattice strains have redistributed around the impact crater, demonstrating the local alteration of the residual strain field. These new findings suggest the localized variation in residual strains should be taken into account while evaluating the service damage evolution of railway axles, especially those affected by high-speed impacts during operation.

論文

Gradient residual stress and fatigue life prediction of induction hardened carbon steel S38C axles; Experiment and simulation

Qin, T. Y.*; Hu, F. F.*; 徐 平光; Zhang, H.*; Zhou, L.*; Ao, N.*; Su, Y. H.; 菖蒲 敬久; Wu, S. C.*

International Journal of Fatigue, 185, p.108336_1 - 108336_13, 2024/08

https://doi.org/10.1016/j.ijfatigue.2024.108336
 被引用回数：20 パーセンタイル：89.57(Engineering, Mechanical)

Gradient distribution of triaxial residual stresses to a depth of several millimeters is retained in middle carbon steel S38C axles after high-frequency induction hardening, which has become a critical concern for fatigue structural integrity. To address this, the axial, hoop, and radial gradient residual strains inside the axles were measured for the first time by advanced neutron diffraction. The SIGINI Fortran subroutine was then adopted to reconstruct the global initial residual stress field from the measured data. Experimental and simulation results show that residual stresses of about -520 MPa (axial), -710 MPa (hoop), and -40 MPa (radial) residual stress were retained below the axle surface. Subsequently, the fatigue crack propagation behavior of S38C axles was numerically investigated in the framework of fracture mechanics. The calculated results clearly show that the compressive residual stresses at a depth of 0?3 mm from the axle surface lead to a low crack growth driving force, and that fatigue cracks do not propagate as long as the crack depth is less than 3.7 mm for hollow S38C axles. These results further indicate that the maximum defect size allowed in routine inspections is acceptable from a safety and economic point of view. Accurate measurement and characterization of the global gradient residual stress field through experiments and simulations can provide an important reference for optimizing the mileage intervals of nondestructive testing (NDT) of surface defects in these surface-strengthened railway axles.

論文

Progress of material characterization techniques based on neutron Bragg-edge transmission imaging

Wang, Y. W.*; 徐 平光; Su, Y. H.; Ma, Y. L.*; Wang, H. H.*

Physics Examination and Testing, 42(4), p.32 - 41, 2024/08

https://doi.org/10.13228/j.boyuan.issn1001-0777.20230085

With the rapid technological development of large spallation neutron source facilities, the neutron beam flux obtained has been greatly improved and neutron imaging techniques have been further developed. Due to the limitation of neutron beam flux, conventional neutron imaging techniques require neutron beams with a wide wavelength range to obtain relatively high neutron beam flux conditions. Recently, spallation neutron sources using large proton accelerators have made it possible to obtain high-flux pulsed neutron beams. Energy (wavelength) resolved neutron imaging technique based on the Bragg edge effect (neutron Bragg edge transmission imaging technique) is expected to have a wide range of applications because of its high energy resolution, high spatial resolution, and ability to detect crystallographic information. The basic principle of this technique is briefly introduced. Several applications in the evaluation of residual strain, phase composition, dislocation density, and oriented structure are also reviewed to play an active role in promoting the wider applications of related technique.

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