論文 - 森田 千尋
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Axial-torsional testing and cyclic plasticity modelling of wire arc additively manufactured steel 査読あり 国際共著
Horisawa E., Meng X., Gardner L., Kitane Y., Sugiura K., Morita C.
Journal of Constructional Steel Research 238 2026年3月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Constructional Steel Research
Wire arc additive manufacturing (WAAM) is a metal 3D printing technique with the potential to produce structural steel elements in a cost-effective fashion. However, there is currently a paucity of data concerning the mechanical behaviour of WAAM steel under uniaxial and multiaxial cyclic loading. This study aims to address this gap via a comprehensive experimental investigation and constitutive modelling of the multiaxial cyclic behaviour of WAAM steel. Cyclic testing featuring axial and torsional loading was conducted on WAAM Grade ER70S-6 steel, and a constitutive model to describe the multiaxial cyclic behaviour of the examined material is proposed. First, radial loading in the biaxial stress plane was conducted to identify the shape of the initial yield surface and the strain development paths of the material. Uniaxial and biaxial cyclic loading tests were performed to investigate the hardening of the material. The experimental results show that WAAM steel exhibits a von Mises isotropic yield surface, with plastic strain developing in the direction normal to the yield surface. The proposed modified two-surface plasticity model accurately reproduces both the uniaxial and multiaxial cyclic stress-strain responses, while offering improved accuracy for the multiaxial ratcheting behaviour compared with the conventional model. The results of this study show that the classical plasticity theory used for conventional steel is also applicable to WAAM steel.
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急速架設可能な緊急仮設橋の構造と管理方法の提案 査読あり
平池 勉, 佐々木 貴信, 冨岡 仁計, 本田 修一, 近広 雄希, 渡部 慎也, 渡辺 浩, 平沢 秀之, 森田 千尋
構造工学論文集 Ａ 72A 818 - 830 2026年3月
担当区分：責任著者 記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：公益社団法人 土木学会
Bridges, which serve to ensure lifelines, have been suffering damage from increasingly severe natural disasters and deterioration due to factors such as aging, resulting in numerous reports of bridges failing to fulfill their role and disrupting public economic activity. This report focuses on the many small and medium-sized bridges currently existing in Japan that are 15m or less in length, and proposes specific bridge plans for quickly restoring traffic. These include mitigating impacts through vehicle restrictions, using leased materials available on the market, and utilizing aluminum and wood. Furthermore, the report provides approximate erection times for steel girders and aluminum structures.
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大気暴露試験を用いたZn-Al溶射およびZn溶射の腐食特性評価 査読あり
森本 菖, 中野 敦, 堀澤 英太郎, 森田 千尋, 押川 渡, 米沢 昇
材料と環境 75 ( 1 ) 14 - 22 2026年1月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：公益社団法人 腐食防食学会
本研究では，Zn-Al溶射，Zn溶射およびZnめっきを用いて，宮崎大学木花キャンパスと宮崎大学延岡フィールドの2地点において大気暴露試験を実施し，それぞれの溶射皮膜の組成の違いによる腐食特性を外観観察，膜厚測定，XRDおよびSEM・EDX分析により比較した．その結果，Zn-Al溶射では暴露2年目においても大きな腐食はみられず，Zn溶射およびZnめっきでは腐食生成物の堆積が確認された．
DOI： 10.3323/jcorr.75.14
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Mechanical behavior of structural steel clad by wire arc thermal spraying 査読あり
Horisawa E., Matsumura M., Matsumoto R., Tanimoto T., Sugiura K., Morita C.
Journal of Constructional Steel Research 234 2025年11月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Constructional Steel Research
Thermal spraying is a surface modification technique in which molten particles are deposited to form protective or functional coatings. This study investigated the mechanical behavior of structural steel components strengthened by wire arc thermal spray cladding. The thermal spraying process was performed using martensitic stainless steel wire to achieve a target cladding thickness of approximately 5 mm. Tensile, compression, and bending tests were conducted to evaluate the mechanical performance of the cladding under various loading conditions. The cladding exhibited a Young's modulus of 70 GPa, approximately one-third that of bulk steel. The tensile strength of the cladding was estimated at 231 MPa, with brittle fracture occurring at a strain of 0.3 %. Despite its limited tensile ductility, the cladding contributed to an increase in axial stiffness in the elastic range. In contrast, under compression, the cladding exhibited ductile nonlinear behavior and failed by vertical cracking. The 0.2 % proof stress of the cladding in compression was 1.3 times that of the substrate, indicating adequate load-bearing capacity under compressive stress. In bending tests, the maximum load of clad steel plates was five times that of unclad steel plates, although cracking and debonding of the cladding were observed. These findings suggest that cladding applied by thermal spraying has mechanical characteristics suitable for structural applications, particularly under compressive stress.
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Study on atmospheric corrosion properties of Zn-30mass% Al and Zn arc thermal sprayed coatings 査読あり
A. Morimoto, A. Nakano and C. Morita
Proceedings of ISSS-PSSC 2025 13 919 - 922 2025年11月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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複合サイクル試験機を用いた機能性防錆塗装の腐食特性に関する基礎的研究
森本 菖, 森田 千尋, 中野 敦, 堀澤 英太郎
宮崎大学工学部紀要 54 29 - 34 2025年10月
担当区分：責任著者 記述言語：日本語 掲載種別：研究論文（大学，研究機関等紀要） 出版者・発行元：宮崎大学工学部
The purpose of this study was to evaluate the corrosion characteristics of various coating systems. To investigate the durability of the coating systems after application in repainting using the equivalent of three types of cleanings, we focused on the rust thickness of black rust formed on the steel surface and the salinity of the black rust adhered to the surface. Test specimens were subjected to accelerated corrosion tests using five different functional anti-corrosion coating systems and the conventional coating Rc-I, and the corrosion characteristics of each coating system were evaluated. As a result, blistering and spot rusting were observed on the test specimens except for the thick-film fluoropolymer paint and Rc-I. It was also found that point rusting and swelling were more likely to occur in the weakly soluble fluorine paint, where the residual rust thickness was greater and the adhered salt concentration was higher. The coating thickness measurement results showed that the weakly soluble fluorine paint, organic-inorganic composite coatings, and thick-film fluoropolymer paint showed a decrease in coating thickness when the residual rust thickness was large and the adhered salinity was high, while the Rc-Ⅰ method showed a decrease in coating thickness only when the residual rust thickness was large and the adhered salinity was moderate. The cross-sectional analysis results showed the presence of black rust Fe3O4 and an increase in residual rust thickness after the accelerated corrosion test.
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CNN AND GAN BASED WEATHERING STEEL APPEARANCE EVALUATION IMPROVED BY IMAGE SIZE AND LOSS FUNCTION 査読あり
Nagatani K., Shigei N., Morita C., Ishizuka Y., Miyajima H.
International Journal of Innovative Computing, Information and Control 21 ( 2 ) 433 - 445 2025年4月
掲載種別：研究論文（学術雑誌） 出版者・発行元：International Journal of Innovative Computing, Information and Control
Weathering steel is a steel material that can maintain its performance outdoors for a long period of time by forming protective rust. Periodic inspection of the rust condition is necessary to maintain this steel in good condition, and CNN-based methods for evaluating the appearance of rust have been studied. One of the problems in improving the classification accuracy of the CNN is how to prepare the rust images for training. The objectives of this paper are 1) to consider rust patch image size and 2) to improve the diversity of the generated images in rust image generation using GAN. From 1), we show that the accuracy can be improved by using large cropping images and shrinking the image when training the model. From 2), we propose SSIM-target loss, which is an improvement of the conventional SSIM loss, and show that it improves the CNN Score. Using methods 1) and 2), we achieved an F1 score of 90.3% for the three-class classification of the rust images, compared to the baseline method’s F1 score of 86.8%.
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耐候性鋼橋梁のさび外観評点と健全性評価に関する考察 査読あり
中島和俊, 加納勇, 安波博道, 今井篤実, 高木優任, 森田千尋
構造工学論文集 71A 351 - 361 2025年3月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：公益社団法人 土木学会
In this study, the appearance rating method, which is now widely used to diagnose the integrity of weathering steel bridges, was reorganized based on photographs and the amount of corrosion in previous studies to clarify the classification of each category. This clearly separated the categories that should be repaired (Rating Number 1) from the others. In addition, it was also possible to determine that the rusting changes over time would not naturally shift to the rating number 1, although there is a possibility that the rusting changes from rating number 5 to rating number 2 would shift sequentially. This has enabled us to propose a more rational method for soundness diagnosis during periodic inspections.
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Numerical study on the melting behavior of annular fuel under accident conditions 査読あり 国際共著
Wang B., Huang M., Meng X., Ouyang X., Huang Y., Matsuda H., Morita C.
Progress in Nuclear Energy 179 2025年1月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Progress in Nuclear Energy
The use of annular fuel in nuclear power plants has been developed to improve their efficiency, safety, and economic viability. Therefore, studying the thermal hydraulic issues of annular fuel is crucial. The melting of annular fuel under accident conditions is equally important. This study uses a novel numerical technique called the Half Boundary Method (HBM) to tackle this issue. With new variables introduced, this method avoids the need for additional continuity equations at the boundary when solving multi-layer composite problems. First, the HBM is used to model a multi-layer composite ring and solve its transient thermal problems, which are then verified. Next, the temperature distribution of annular fuel under operational conditions is calculated, and the results are compared to validate HBM's accuracy. Based on these findings, simulations are conducted to model the melting phase transitions of annular fuel during Loss of Coolant Accidents (LOCAs) and Reactivity Insertion Accidents (RIAs).
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Improvement of GAN-based Training Image Generation for CNN-based rust Evaluation of Weathering Steel 査読あり
Nagatani K., Shigei N., Morita C., Ishizuka Y., Miyajima H.
ACM International Conference Proceeding Series 40 - 47 2024年12月
掲載種別：研究論文（学術雑誌） 出版者・発行元：ACM International Conference Proceeding Series
Weathering steel is a steel material that produces a protective rust layer on the surface of the steel that suppresses the propagation of corrosion. Periodic inspection of the rust condition is necessary to maintain this steel in good condition, and CNN-based methods for evaluating the appearance of rust have been studied. One of the problems in improving the classification accuracy of the CNN is how to prepare the rust images for training. Since it is difficult to collect rust images in the real world, it has been studied to train CNN with rust images generated by GANs. Conventional GANs have the problem that when a large number of images are generated, the generated images are biased toward similar ones. The scope of this paper is to improve the accuracy of CNN using GAN-generated images in classification tasks of rust conditions of weathering steel. The specific objectives of this study are to improve the diversity of images generated by GANs and thereby improve the accuracy of CNNs. To improve image diversity in GAN-based image generation, we propose to use Wasserstein GAN with Gradient Penalty (WGAN-GP), in addition to Conditional GAN (CGAN), and to introduce SSIM (Structural Similarity) and LBP (Local Binary Pattern) as loss functions, in addition to L1 and L2 losses. Then, the images generated by the proposed five types of GANs are applied to the training of CNNs. Comparison between the proposed GANs and the conventional CGAN shows that 1) the proposed GANs can reduce the SSIM similarity of the generated images by up to 1/4, and 2) in the classification of three classes of rust images, the use of the generated images of the proposed GANs can improve the F1 score by up to about 4%pt. Overall analysis shows that WGAN-GP-based is better than CGAN-based and that the newly introduced SSIM, LBP, L1 and L2 losses improve both similarity and classification accuracy.
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A boundary-type algorithm based on the discrete ordinates for neutron transport equation 査読あり 国際共著
Cheng Y.T., Huang M., Ouyang X.P., Matsuda H., Morita C.
Engineering Analysis with Boundary Elements 169 2024年12月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Engineering Analysis with Boundary Elements
The spatial distribution of neutron flux in the core of a nuclear reactor plays a crucial role in ensuring nuclear safety. It can be determined by solving the neutron transport equation, where computational resource consumption is gradually receiving more attention, especially in problems with multiple reflective boundary conditions. It is common practice to assume initial boundary values in one angular direction to obtain a global solution, and then use reflective boundary conditions to solve for the other directions, iterating until convergence. However, this approach has the drawback of requiring the global solution, and each iteration necessitates storing the neutron flux values, consuming time and storage space. In order to address this issue, this paper proposes a precise and efficient boundary-type method, the Half Boundary Method (HBM). This method establishes relationships between adjacent node values through integration and mathematical deduction, ultimately obtaining the relationship among any node and the boundary values in any direction. As a result, iteration is only required for boundary values, reducing the iteration amount and thus saving time and storage space. Using the discrete ordinate (SN) method for angular discretization and HBM for spatial discretization, this paper solved the steady-state neutron transport equation for two-dimensional systems modeled with Cartesian geometry. The method is validated using several benchmark problems, including the 2D ISSA benchmark, the 2D mono-group k-eigenvalue problem and BWR rod bundle test problem. All of these problems demonstrate good results and effectively reduced computational time.
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Nakano A., Toyota Y., Morita C., Yasui K., Oshikawa W., Yonezawa N.
International Journal of Steel Structures 2024年9月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：International Journal of Steel Structures
This paper presents the results of a study comparing the initial corrosion characteristics of thermal spray coatings on Zn, Zn-Al, and Al–Mg thermal spray coatings after one year atmospheric exposure tests at two atmospheric environment sites. The thermal spray coatings were obtained by electroric arc spraying of various metals onto a carbon steel substrate. Atmospheric exposure tests were also conducted for outdoor accelerated exposure tests in which test specimens were applied with artificial seawater. The corrosion properties of these spray coatings were evaluated by surface analysis, film thickness measurements, cross-sectional analysis and anodic/cathodic polarization measurement. After one year of atmospheric exposure testing, white, granular corrosion products were observed on the surface of the Zn and Zn-Al thermal spray coatings, while no significant changes were observed in the Al–Mg thermal spray coating. Similar results were obtained for the surfaces of test specimens in atmospheric exposure tests with artificial seawater. The thickness of the thermal spray coating increased for the Zn thermal spray coating, while no significant change was observed for the other thermal spray coatings. Thus, differences in corrosion behavior were observed due to the composition of the thermal spray coatings. The initial corrosion behavior of the thermal spray coatings was also investigated based on the results of coating morphology and cross-sectional elemental distribution of the coatings.
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特集「建造物とインフラ管理における計測技術」の編集にあたって 招待あり
森田 千尋
実験力学 24 ( 2 ) 42 - 42 2024年6月
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Yasui K., Sakaida Y., Yamamura K., Minamimagari M., Horisawa E., Morita C., Kinoshita H.
Sustainability (Switzerland) 16 ( 12 ) 2024年6月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Sustainability (Switzerland)
Bora is a granular volcanic pumice with a certain degree of hardness. In this study, we investigated the possibility of using fired Bora as a substitute for fine sand in mortar. The objective was to develop a lightweight pavement block with extremely high permeability using fired Bora. Initially, the changes in hardness and density of Bora particles fired at different temperatures were examined. The bending strength of mortar containing fired Bora as a fine aggregate was also evaluated. Subsequently, we fabricated a permeable pavement block with a hybrid structure, comprising a mortar containing the fired Bora and a porous material with large-sized Bora particles bonded using cement paste. We examined its bending strength and permeability and performed a quantitative analysis of the bending stress distribution on the block using the finite element method. The hardness of Bora significantly increased when fired at temperatures exceeding 900 °C; hence, Bora fired at 1100 °C can be used as an effective substitute for crushed sand in mortar. Furthermore, the results confirmed that the use of fired Bora enabled the production of lightweight pavement blocks with extremely high permeability that satisfied the bending strength criterion.
DOI： 10.3390/su16124888
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Statistical damage constitutive model for rocks considering temperature effects and its validation 査読あり 国際共著
Wei C., Zhao C., Zhao C., Matsuda H., Morita C.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) 55 ( 3 ) 1056 - 1067 2024年3月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology)
In order to predict and evaluate the stability of deep high-temperature rock masses, theoretical derivation methods were used to study the constitutive relationship of rocks under (after) temperature action. Firstly, based on existing rock statistical damage constitutive models, the influence of temperature on rock damage variables was considered, and parameters such as damage variable correction coefficient, damage initiation stress, and initiation strain were introduced. Secondly, it is assumed that the strength of the microelements follows a power function distribution and conforms to the Hoek- Brown (H-B) strength criterion. In response to the drawback that statistical damage constitutive models cannot reflect the strong prepeak microcrack compaction effect, corresponding model correction coefficients were introduced. Thirdly, a rock statistical damage constitutive model considering temperature effect was established, and the expression of model parameters was determined. Finally, the accuracy of the model was verified by comparing the data obtained from uniaxial and conventional triaxial compression tests on granite under different temperature conditions with the calculation results of the model in the literature. The results show that the calculation results of the proposed model are consistent with the experimental results in literature in terms of numerical values, distribution patterns and trends. For each stage of the whole process σ-ε curve, the calculation result of the model in this paper is better than that of the constitutive model in the literature, and fits with the test curve better, which can better reflect the damage constitutive characteristics of rock under (after) high temperature. The parameters of the model are conventional and suitable for rocks under various temperature-pressure combination conditions.
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宮崎県内の耐候性鋼橋梁におけるさび状態の経年変化
清瀬啓文，森田千尋，別府渓太，安井賢太郎
九州橋梁・構造工学研究会シンポジウム論文集 11 54 - 58 2023年12月
担当区分：責任著者 記述言語：日本語 掲載種別：研究論文（研究会，シンポジウム資料等）
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Atmospheric corrosion properties of thermally sprayed Zn, Zn–Al, and Al-Mg coatings exposed under different atmospheric environment 査読あり
Y. Toyota, A. Nakano, C. Morita, K. Yasui, W. Oshikawa and N. Yonezawa
Proceedings of ISSS 2023 12 303 - 306 2023年11月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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A Study on Bridge Inspection Method Using UAV and SfM 査読あり
J. Sakoda, C. Morita, K. Yasui and A. Demizu
Proceedings of ISSS 2023 12 299 - 302 2023年11月
担当区分：責任著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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球磨川における被災橋梁の復旧状況調査とモバイルブリッジの実用性の検討
豊田祐樹，上別府尚弘，森田千尋
宮崎大学工学部紀要 52 31 - 39 2023年11月
担当区分：責任著者 記述言語：日本語 掲載種別：研究論文（大学，研究機関等紀要）
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Half boundary method for two-dimensional steady-state nonlinear convection-diffusion equations 査読あり 国際共著
Meng X., Huang M., Wang B., Li Y., Cheng Y., MORITA C.
Engineering Analysis with Boundary Elements 150 187 - 198 2023年5月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Engineering Analysis with Boundary Elements
In this research, half-boundary method (HBM) is developed for nonlinear convection-diffusion equations (CDEs) which play an important role in applied mathematics and physics. The HBM is based on the variable relationship between the nodes inside the domain and the nodes on half of the boundaries, making it ideal for reducing the maximum order of matrix and calculation memory storage. Besides, the HBM can solve discontinuous problems directly without adding continuity conditions due to the use of the mixed variables. The effectiveness and accuracy of the proposed algorithm are investigated mainly for the two-dimensional(2D) steady-state Burgers’ equation, the material nonlinear 2D CDEs and the system of 2D Burgers’ equations. The results show the excellent performance of the HBM in simulating flow and heat transfer, especially for convection domination.