論文 - 森田 千尋
-
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.
-
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%.
-
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.
-
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).
-
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.
-
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.
-
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.
-
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
-
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
-
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.
-
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）
-
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）
-
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）
-
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）
-
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.
-
防災・減災のための緊急仮設橋の設計および設計基準の課題 査読あり
渡邊学歩，佐々木貴信，森田千尋，小林博之，勝呂翔平，松田伊佐雄，木下幸治
構造工学論文集 69A 1258 - 1268 2023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
In this study, the operational records of temporary bridges, definitions of temporary bridges, and applicable technical standards were reviewed, and these issues were clarified. The results of trial designs of emergency bridges show that the elimination of regulation of the deflection enables the rational design and construction of temporary bridges using readily available materials. In addition, the necessity of technological development for the design of structural details, clarification of performance requirements, and standardization of design is proposed to reduce the construction cost of temporary bridges and to speed up their construction.
-
中小規模橋梁の復元設計におけるSfM活用の基礎的検討
本多雅匠，塩竃柚貴，森田千尋，安井賢太郎，中丸ゆかり
宮崎大学工学部紀要 51 7 - 14 2022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）
-
Baggingと複数のパッチ画像を用いたCNN識別器による耐候性鋼材のさびの外観評価手法 査読あり
有村和也，重井徳貴，森田千尋，石塚洋一，宮島廣美
知能と情報 34 ( 2 ) 533 - 538 2022年5月
記述言語：日本語 掲載種別：研究論文（学術雑誌）
-
CFD investigation for a 7-pin wrapped-wire fuel assembly with different wires 査読あり 国際共著
Lin J., Huang M., Zhang S., Wang B., Huang J., Matsuda H., Morita C.
Annals of Nuclear Energy 164 2021年12月
担当区分：最終著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Annals of Nuclear Energy
The fuel rods of the fast reactor are radially and axially fixed and supported by wrapped-wire. The wrapped-wire not only prevents the fuel rod from vibrating but also stirs the coolant, thereby enhancing heat transfer. This paper uses the SST k–ω turbulence model and commercial CFD software to investigate the effect of the number of the wrapped-wires on flow field. The results show that under normal operating conditions, the increase of the number of wrapped wires will increase the pressure difference, but it is conducive to the mixing of the flow field due to the regular eddy current phenomena caused by uneven pressure distribution, which is one of the reasons that affect the convective heat transfer of fuel assemblies.
-
Zhang R., Zhao C., Yang C., Xing J., Morita C.
Computers and Geotechnics 140 2021年12月
担当区分：最終著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Computers and Geotechnics
Understanding the mechanisms of crack initiation and development is important for utilizing the hydraulic fracturing in practical engineering applications. In this study, hydraulic fracturing experiments were conducted on granite specimens containing a single pre-existing flaw, and the failure processes were analyzed using the digital image correlation method. A flat-jointed bonded particle model was built with a modified fluid flow algorithm to better understand the fracture behavior under the experimental conditions. Combining the DIC strain fields and the simulated displacement fields, we found that shear behavior with a small value also emerges ahead of the tips of the microcracks and was covered by the subsequent tensile behavior, as a result, shear strain could not be observed in the experiments. A comparison between the strain localization and the microcracks revealed that the fracturing process observed in the experiments had two stages: the isolated strain localization formed during Stage I, mainly resulting from the increase in microcracks, and the continuous high tensile strain path formed during Stage II. Additionally, the effect of the different flaw inclination angles was discussed from two perspectives: the different types of macrocracks and the change in the fracturing liquid pressure.