Updated on 2024/05/01

写真a

 
SAKAMOTO Junji
 
Organization
Faculty of Environmental, Life, Natural Science and Technology Assistant Professor
Position
Assistant Professor
External link

Degree

  • 博士(工学) ( 2013.3   九州大学 )

Research Interests

  • Metal Fatigue

  • Vibration

  • Risk

  • Mechanics of materials

Research Areas

  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Social systems engineering

  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Safety engineering

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Mechanics of materials and materials

Education

  • Kyushu University   工学府   機械工学専攻

    2010.4 - 2013.3

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    Country: Japan

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  • Kyushu University   工学府   機械科学専攻

    2009.4 - 2010.3

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    Country: Japan

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  • Kyushu University   工学部   機械航空工学科

    2005.4 - 2009.3

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    Country: Japan

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Research History

  • Okayama University   学術研究院環境生命自然科学学域   Assistant Professor

    2023.4

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    Country:Japan

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  • Okayama University   学術研究院自然科学学域   Assistant Professor

    2021.4 - 2023.3

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    Country:Japan

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  • Yokohama National University   リスク共生社会創造センター

    2018.12 - 2019.3

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    Country:Japan

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  • Okayama University   Graduate School of Natural Science & Technology   Assistant Professor

    2018.9 - 2021.3

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    Country:Japan

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  • Yokohama National University   Institute of Advanced Sciences   Assistant Professor

    2017.6 - 2018.8

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    Country:Japan

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  • Yokohama National University   Center for Creation of Symbiosis Society with Risk   Assistant Professor

    2015.10 - 2017.5

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    Country:Japan

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  • Yokohama National University   Center for Risk Management and Safety Sciences   Researcher

    2014.11 - 2015.9

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    Country:Japan

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  • Seoul National University of Science and Technology   Department of Mechanical & Automotive Engineering

    2013.5 - 2014.10

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    Country:Korea, Republic of

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  • Kyushu University   Department of Mechanical Engineering

    2013.4 - 2013.8

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    Country:Japan

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Professional Memberships

  • THE IRON AND STEEL INSTITUTE OF JAPAN

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  • THE JAPAN SOCIETY OF MECHANICAL ENGINEERS

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  • THE SOCIETY OF MATERIALS SCIENCE, JAPAN

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Papers

  • Relationship between cyclic tensile properties of cellulose nanofiber reinforced natural rubber and volume fraction of bound rubber obtained from swelling tests Reviewed

    OKUI Kento, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, SAKAKIBARA Keita

    Transactions of the JSME (in Japanese)   90 ( 932 )   24-00008 - 24-00008   2024.4

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Mechanical Engineers  

    In recent years, environmental concerns have led to a demand for sustainable materials, and natural rubber (NR) reinforced with cellulose nanofibers (CNFs) has been attracting attention as one such material. When CNFs are added to NR, the elastic modulus is greatly improved. This is considered to be caused by deformation constraint of NR by reinforcing CNFs. On the other hand, it is known that there exists a region around reinforcing fibers where the rubber is tightly connected to the surface of fibers, which is called bound rubber. The volume fraction of the bound rubber is usually measured by swelling tests using organic solvent. In this paper, we focused on the relationship between the tensile properties of NR reinforced with CNFs and the volume fraction of bound rubber. Firstly, cyclic tensile tests were performed using plate specimens of CNF-reinforced NR and the effect of reinforcing CNFs on the tensile properties of CNF-reinforced NR and their change with loading cycles were investigated. Then, the swelling tests were conducted for similar specimens and the volume fraction of the bound rubber was evaluated. It was found from a series of experimental results that tensile deformation resistance of NR increased largely by adding 5 phr (4.8 mass%, 3.2 vol.%) of CNFs but that this increase decreased from the second loading cycle. Moreover, a clear relationship was found between the tensile deformation resistance of CNF-reinforced NR and the volume fraction of bound rubber. These results suggest that the tensile deformation resistance of CNF-reinforced NR can be evaluated by swelling tests.

    DOI: 10.1299/transjsme.24-00008

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  • Vibration change and crack propagation under bending vibration of aluminum alloy Reviewed

    SAKAMOTO Junji, TADA Naoya, UEMORI Takeshi

    Transactions of the JSME (in Japanese)   90 ( 930 )   23-00246 - 23-00246   2024.2

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Mechanical Engineers  

    In this study, aluminum alloy specimens were subjected to bending vibrations at different vibration frequencies near the first resonance frequency in order to investigate the vibration changes associated with crack propagation. Bending displacement, crack length, and strains at several parts of the specimen were measured during the bending vibration tests. As a result, it was confirmed that when the vibration frequency was lower than the initial first resonance frequency, the vibration amplitude increased with the crack length, and when the vibration frequency was higher than the initial first resonance frequency, the vibration amplitude decreased with an increase in the crack length. This is due to the decrease in the first resonance frequency due to the material damage. The relationship between the change of bending displacement amplitude and the crack length during vibration of the specimens can be organized using the slope (dΔεx2/dfv) of the relationship between the strain range and the vibration frequency for the undamaged specimen. This might be due to the strong correlation between the decrease in the first resonance frequency and the crack size when the crack initiation location is limited in the material. Moreover, based on the relationship between the change of bending displacement amplitude and the crack length, the stress intensity factor range (ΔK) was estimated by incorporating the load change into the crack length. By using the modified ΔK, the crack growth rate during bending vibration could be predicted.

    DOI: 10.1299/transjsme.23-00246

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  • Prediction of slip activity of crystal grains around semi-circular and semi-elliptical notches in thin-sheet specimens of pure titanium using formulated macroscopic stress distribution and crystal orientation Reviewed

    Naoya Tada, Takeshi Uemori, Junji Sakamoto

    Engineering Failure Analysis   107623 - 107623   2023.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.engfailanal.2023.107623

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  • Tensile properties and slip deformation behavior of pure titanium thin wire with a small diameter-to-grain-size ratio Reviewed

    Junji Sakamoto, Naoya Tada, Takeshi Uemori

    Materials Science and Engineering A   863   144532   2023.1

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    To investigate the tensile properties and slip deformation behavior of pure titanium thin wires with a small ratio of the diameter to the grain size, tensile tests and a stepwise tensile test were performed using specimens with a diameter of approximately 170 μm and grain sizes of 17 and 87 μm, corresponding to diameter-to-grain-size ratios of 10 and ∼2, respectively. The specimen with a diameter-to-grain-size ratio of 10 fractured through the growth of voids. The fracture morphology was similar to that of the bulk specimens. On the other hand, for specimens with a diameter-to-grain-size ratio of 2, fracture occurs owing to the local deformation, in which primary slip systems are activated in each grain. The stepwise tensile test of the specimen with a diameter-to-grain-size ratio of 2 indicated that the slip deformation tended to occur from the large grains. Moreover, the activities of the slip systems of grains were evaluated using the Schmid factor (SF) and critical resolved shear stress (CRSS) of each slip system. It was noted that slip systems with the highest SF∙CRSS−1 were activated for 30 out of 33 grains.

    DOI: 10.1016/j.msea.2022.144532

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  • Application of Complex-Step Derivative Approximation Method to Crystal Plasticity Analysis of Commercially Pure Titanium Sheet

    上森武, 多田直哉, 坂本惇司

    チタン   70 ( 2 )   158 - 163   2022.4

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  • Effect of mechanical surface treatment and post-treatment polishing on tensile strength and fatigue life of high-speed tool steel Reviewed

    N. Karunathilaka, N. Tada, T. Uemori, J. Sakamoto, R. Hamamitsu, M. Fujii, Y. Omiya, M. Kawano

    International Journal of Peening Science and Technology   2 ( 1 )   35 - 60   2022

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  • Effect of resin lamination on tensile strength characteristics of SUS304 stainless steel thin film Reviewed

    Junji Sakamoto, Naoya Tada, Takeshi Uemori

    The International Journal of Advanced Manufacturing Technology   116 ( 3-4 )   1081 - 1088   2021.9

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    The objective of this study is to clarify the effect of resin lamination on the tensile strength characteristics of SUS304 stainless steel thin films. We conducted tensile and stepwise tensile tests using several types of specimens prepared with 20-μm- and 40-μm-thick SUS304 films, 25-μm-thick polypropylene (PP) film, and 6-μm-thick polyethylene terephthalate (PET) film. Their macroscopic and microscopic tensile deformation behaviors were observed using an optical microscope and a reflection-configured digital holographic microscope, respectively. As a result, laminating the PP or PET films onto the SUS film did not significantly change the macroscopic and microscopic strain changes against the tensile load or microscopic surface changes in the low-strain region. Laminating the PET film onto the SUS film did not reduce the fracture strain, whereas laminating the PP film onto the SUS film did reduce it. One of the reasons may be that burrs formed on the side surface of the PP/SUS laminate. Polishing the side surface of the PP/SUS laminate may suppress the reduction in its fracture strain. The reduction of the fracture strain due to the PP lamination in the 20 μm thick SUS film was larger than that of the 40-μm-thick SUS film. In thin SUS films, small stress concentrators that have almost no effect on macroscopic and microscopic deformation might significantly reduce the fracture strain.

    DOI: 10.1007/s00170-021-07510-8

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  • Prediction of the fracture location by tensile tests of gray cast iron based on the dimensional changes of graphite flakes

    Naoya Tada, Takeshi Uemori, Junji Sakamoto

    Journal of Pressure Vessel Technology, Transactions of the ASME   143 ( 2 )   2021.4

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    © 2021 American Society of Mechanical Engineers (ASME). All rights reserved. Gray cast iron has been used as a component in various mechanical parts, such as the blocks and heads of automobile and marine engines, cylinder liners for internal combustion engines, and machine tool bases. It is desirable because of its good castability and machinability, damping characteristics, and high performance-To-cost ratio. On the other hand, weak graphite flakes present in gray cast iron serve as stress concentrators and adversely affect the material strength. Therefore, it is crucial to examine the relationship between the distribution of graphite flakes and the strength or fracture of gray cast iron. In this study, tensile tests on gray cast iron were carried out using a plate specimen and observed by scanning electron microscopy, and the microscopic deformation was observed on the specimen surface. Particularly, the change in the size of graphite flakes during the tensile tests was examined, and the observed trend was discussed. The experimental results reveal that the dimensional changes in the graphite flakes vary in the observed area and that the final fracture occurs in an area where a large dimensional change is observed, suggesting that the fracture location or critical parts of gray cast iron can be predicted from the dimensional changes of the graphite flakes at an early stage of deformation.

    DOI: 10.1115/1.4048063

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  • Finite element study of the effect of internal cracks on surface profile change due to low loading of turbine blade Reviewed

    Junji Sakamoto, Naoya Tada, Takeshi Uemori, Hayato Kuniyasu

    Applied Sciences (Switzerland)   10 ( 14 )   4883 - 4883   2020.7

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    © 2020 by the authors. Turbine blades for thermal power plants are exposed to severe environments, making it necessary to ensure safety against damage, such as crack formation. A previous method detected internal cracks by applying a small load to a target member. Changes in the surface properties of the material were detected before and after the load using a digital holographic microscope and a digital height correlation method. In this study, this technique was applied in combination with finite element analysis using a 2D and 3D model simulating the turbine blades. Analysis clarified that the change in the surface properties under a small load varied according to the presence or absence of a crack, and elucidated the strain distribution that caused the difference in the change. In addition, analyses of the 2D model considering the material anisotropy and thermal barrier coating were conducted. The difference in the change in the surface properties and strain distribution according to the presence or absence of cracks was elucidated. The difference in the change in the top surface height distribution of the materials with and without a crack was directly proportional to the crack length. As the value was large with respect to the vertical resolution of 0.2 nm of the digital holographic microscope, the change could be detected by the microscope.

    DOI: 10.3390/app10144883

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  • Leak frequency analysis for hydrogen-based technology using bayesian and frequentist methods Reviewed

    Mahesh Kodoth, Shu Aoyama, Junji Sakamoto, Naoya Kasai, Yehia Khalil, Tadahiro Shibutani, Atsumi Miyake

    Process Safety and Environmental Protection   136   148 - 156   2020.4

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    © 2020 Institution of Chemical Engineers Dealing with hazardous environments such as hydrogen poses considerable risks to property, people, and the environment. Leak frequency analysis is a method of understanding the characteristics of risks at hydrogen refueling stations (HRSs). This paper proposes leak rate estimation using time-based evaluation methods that utilize historical HRS accident information. In addition, leak frequency estimates from another two methods (non-parametric and leak-hole-size) were examined. In the non-parametric approach, the leak frequency is estimated based on a Bayesian update. The results from these three approaches are summarized to understand the trend of leak rate data. The leak rate data from the time-based method displays a similar trend to the leak size based method. However, the non-parametric method tends to be conservative due to high failure observations (new evidences) during the Bayesian update. Finally, the unrevealed leak time was calculated as a function of the leak frequency. The quantitative insights of this study can be used to set performance standards for the availability and reliability in the operation and maintenance of HRSs.

    DOI: 10.1016/j.psep.2020.01.025

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  • Analysis of the change of direct current potential difference and diameter distribution of thin pure titanium wire subjected to tensile and fatigue loads for fracture prediction Reviewed

    SAKAMOTO Junji, TAKAGI Yusuke, UEMORI Takeshi, TADA Naoya

    Transactions of the JSME (in Japanese)   86 ( 882 )   19 - 00351-19-00351   2020.2

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Mechanical Engineers  

    <p>Pure titanium thin wires have been used for medical fields. It is important to investigate the possibility of non-destructive inspection of pure titanium thin wires for the safety utilization of them. In order to investigate a fracture prediction method for a pure titanium thin wire, we performed tensile and fatigue tests and a finite element analysis to analyze the changes of direct current potential difference and diameter distribution of the pure titanium thin wire during tensile and fatigue tests. It was found that a direct current potential difference method may be available for evaluating the tensile and fatigue damages of the pure titanium thin wire. In the tensile and fatigue tests, the normalized direct current potential difference increased almost linearly with an increase in the nominal strain, and a sign of an increase of the normalized direct current potential difference was observed when the fatigue crack propagated. Therefore, the nondestructive inspection could be conducted by setting a tolerance value of the normalized direct current potential difference, or detecting a sign of an increase in the normalized direct current potential difference. In addition, a method of predicting the fracture location from the diameter distribution change of the pure titanium thin wire was studied. The method could be applied to tensile and fatigue fractures.</p>

    DOI: 10.1299/transjsme.19-00351

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  • How knowledge about or experience with hydrogen fueling stations improves their public acceptance Reviewed

    Shunichi Hienuki, Yoshie Hirayama, Tadahiro Shibutani, Junji Sakamoto, Jo Nakayama, Atsumi Miyake

    Sustainability (Switzerland)   11 ( 22 )   6339 - 6339   2019.11

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    © 2019 by the authors. Hydrogen, which is expected to be a popular type of next-generation energy, is drawing attention as a fuel option for the formation of a low-carbon society. Because hydrogen energy is different in nature from existing energy technologies, it is necessary to promote sufficient social recognition and acceptability of the technology for its widespread use. In this study, we focused on the effect of initiatives to improve awareness of hydrogen energy technology, thereby investigating the acceptability of hydrogen energy to those participating in either several hydrogen energy technology introduction events or professional seminars. According to the survey results, participants in the technology introduction events tended to have lower levels of hydrogen and hydrogen energy technology knowledge than did participants in the hydrogen-energy-related seminars, but confidence in the technology and acceptability of the installation of hydrogen stations near their own residences tended to be higher. It was suggested that knowledge about hydrogen and technology could lead to improved acceptability through improved levels of trust in the technology. On the other hand, social benefits, such as those for the environment, socioeconomics, and energy security, have little impact on individual levels of acceptance of new technology.

    DOI: 10.3390/su11226339

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  • オーステナイト系ステンレス鋼XM-19の疲労強度と破面解析 Reviewed

    坂本惇司, 山本翔太, 澁谷忠弘, 志賀優多, 竹花立美, 佐野尊

    JCOSSAR2019論文集   9   2019.10

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publishing type:Research paper (conference, symposium, etc.)  

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  • Prediction of fracture location in tensile test of short-fiber-self-reinforced polyethylene composite plates Reviewed

    Naoya Tada, Ming Jin, Takeshi Uemori, Junji Sakamoto

    American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP   3   2019

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    © 2019 ASME Composite materials such as carbon-fiber-reinforced plastics (CFRP) and glass-fiber-reinforced plastics (GFRP) have been attracting much attention from the viewpoint of lightweight solution of automobiles and airplanes. However, the recyclability of these composite materials is not sufficient and the environmental load is large. Recently, self-reinforced polymer (SRP), in which similar polymer is used for reinforcing fibers and matrix, has been proposed. High-density polyethylene (HDPE) reinforced with ultra-high-molecular-weight polyethylene (UHMWPE) fibers, so-called self-reinforced PE (SRPE), is one of the promising thermoplastic composites. In this study, SRPE plates were made and the tensile tests were carried out. After the effect of reinforcement of UHMWPE fibers was evaluated on the basis of the tensile strength, the relationship between the distribution of UHMWPE fibers and the location of the final fracture line was examined. It was found from these experimental results that the fracture tends to occur along the regions with low area fraction of fibers or along those with low area fraction of fiber/matrix boundaries. This fact suggests that the fracture location of SRPs is predictable from the distribution of reinforcing fibers.

    DOI: 10.1115/PVP2019-93546

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  • Evaluating uncertainty in accident rate estimation at hydrogen refueling station using time correlation model Reviewed

    Mahesh Kodoth, Shu Aoyama, Junji Sakamoto, Naoya Kasai, Tadahiro Shibutani, Atsumi Miyake

    International Journal of Hydrogen Energy   43 ( 52 )   23409 - 23417   2018.12

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    © 2018 Hydrogen Energy Publications LLC Hydrogen, as a future energy carrier, is receiving a significant amount of attention in Japan. From the viewpoint of safety, risk evaluation is required in order to increase the number of hydrogen refueling stations (HRSs) implemented in Japan. Collecting data about accidents in the past will provide a hint to understand the trend in the possibility of accidents occurrence by identifying its operation time However, in new technology; accident rate estimation can have a high degree of uncertainty due to absence of major accident direct data in the late operational period. The uncertainty in the estimation is proportional to the data unavailability, which increases over long operation period due to decrease in number of stations. In this paper, a suitable time correlation model is adopted in the estimation to reflect lack (due to the limited operation period of HRS) or abundance of accident data, which is not well supported by conventional approaches. The model adopted in this paper shows that the uncertainty in the estimation increases when the operation time is long owing to the decreasing data.

    DOI: 10.1016/j.ijhydene.2018.10.175

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  • Analysis of fatigue damage of aluminium alloy under multiaxial random vibration Reviewed

    Junji Sakamoto, Tadahiro Shibutani

    Procedia Structural Integrity   13   529 - 534   2018.12

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (international conference proceedings)  

    DOI: 10.1016/j.prostr.2018.12.087

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  • Evaluation of safety measures of a hydrogen fueling station using physical modeling Reviewed

    Junji Sakamoto, Hitoshi Misono, Jo Nakayama, Naoya Kasai, Tadahiro Shibutani, Atsumi Miyake

    Sustainability (Switzerland)   10 ( 11 )   3846 - 3846   2018.10

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    © 2018 by the authors. Hydrogen fueling stations are essential for operating fuel cell vehicles. If multiple safety measures in a hydrogen fueling station fail simultaneously, it could lead to severe consequences. To analyze the risk of such a situation, we developed a physical model of a hydrogen fueling station, which, when using, the temperature, pressure, and flow rate of hydrogen could be simulated under normal and abnormal operating states. The physical model was validated by comparing the analytical results with the experimental results of an actual hydrogen fueling station. By combining the physical model with a statistical method, we evaluated the significance of the safety measures in the event wherein multiple safety measures fail simultaneously. We determined the combinations of failures of safety measures that could lead to accidents, and suggested a measure for preventing and mitigating the accident scenario.

    DOI: 10.3390/su10113846

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  • Potential failure mode identification of operational amplifier circuit board by using high accelerated limit test Reviewed

    Junji Sakamoto, Ryoma Hirata, Tadahiro Shibutani

    Microelectronics Reliability   85   19 - 24   2018.6

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier Ltd  

    In this study, the potential failure modes of a small operational amplifier circuit board were investigated. The high accelerated limit test (HALT) was employed to identify the failure modes under multi-axial vibration and temperature loadings. Five stress tests, specifically, low and high temperature, vibration, thermal shock, and composite profiles were performed. An aluminum electrolytic capacitor was damaged under the low temperature process, whereas the capacitance of a ceramic capacitor decreased under the high temperature process. The vibration test revealed that mechanical fatigue occurs at the terminal leads of aluminum electrolytic capacitors. The HALT also revealed coupled effects between high and low temperature processes and vibration.

    DOI: 10.1016/j.microrel.2018.04.005

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  • Effects of the shape of small flaws and damage due to a focused ion beam on the fatigue strength characteristics of annealed medium‑carbon steel Reviewed

    Junji Sakamoto, Shigeru Hamada, Hiroshi Noguchi

    Engineering Failure Analysis   87   49 - 68   2018.5

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    Fatigue tests and hardness tests were conducted in order to clarify the effects of the shapes of small flaws and damage caused by a focused ion beam (FIB) on the fatigue strength characteristics of annealed medium‑carbon steel. The notch root radius of the flaw at the branch point dominates the type of the fatigue limit and was found to be approximately 50 μm, a value that was significantly smaller than the 500 μm of two-dimensional notches in steel. The effect of the FIB-damaged layer on fatigue crack initiation from the FIB-milled notch in the steel was negligible. Moreover, the present study indicated that the effect of the FIB-damaged layer on the fatigue crack initiation at the FIB-milled notch could be evaluated simply by using a hardness test for the other materials and FIB conditions.

    DOI: 10.1016/j.engfailanal.2018.02.005

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  • Risk assessment of hydrogen fueling station and its implementation to society

    三宅 淳巳, 坂本 惇司

    空気清浄 : コンタミネーションコントロール   55 ( 5 )   311 - 318   2018

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  • Applying a comprehensive societal risk framework to hydrogen fueling stations

    Atsumi Miyake, Junji Sakamoto, Shunichi Hienuki, Jo Nakayama, Yu Ichiro Izato, Kazuhiko Noguchi

    Global Congress on Process Safety 2018, GCPS 2018 - Topical Conference at the 2018 AIChE Spring Meeting and 14th Global Congress on Process Safety   4   2538 - 2547   2018

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    © GCPS 2018.All right reserved. New perspectives on a comprehensive societal risk framework for technological systems are introduced and discussed in relation to an example application involving a hydrogen fueling station for fuel cell vehicles. The comprehensive societal risk framework consists of not only technological and economic risks, but also environmental and societal risks. This framework will be indispensable to risk communication efforts and initiatives to foster the public acceptance of technological systems.

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  • Finite element analysis of thermal and mechanical stresses due to the grain anisotropy of polycrystalline beta-Sn Reviewed

    Junji Sakamoto, Hisakazu Ohara, Tadahiro Shibutani

    MICROELECTRONICS RELIABILITY   71   29 - 34   2017.4

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    In order to investigate the stress and strain distributions caused by the grain anisotropy of polycrystalline beta-Sn, a finite-element (FE) analysis was conducted using a polycrystalline model that considers the effect of grain anisotropy on the elastic and plastic properties. Even in the case of thermal free expansion with a temperature change of 75 degrees C, plastic strains can be generated locally in polycrystalline beta-Sn. This might be due to the high anisotropy of the thermal expansion coefficient and the low yield strength of beta-Sn. It was found that both in-phase and out of-phase thermal stresses can be present in the polycrystalline beta-Sn simultaneously. The highest stress and strain appeared in the grains whose orientation is relatively different from those of neighboring grains, near the grain boundaries. This might cause the formation of a grain boundary void in the Pb-free solder. Comparing the strain distribution due to the thermal expansion coefficient anisotropy and the Young's modulus anisotropy, it was determined that the maximum value of the plastic strain due to the thermal expansion coefficient anisotropy is approximately 10% higher than that due to the anisotropy of Young's modulus, and the high strain areas are also different in the two cases. The thermo-mechanical fatigue life of beta-Sn might be shorter than that estimated using the isothermal low cycle fatigue life at the same level as the macroscopic strain and could not be estimated by the previous method. (C) 2017 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.microrel.2017.02.009

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  • Simulation-based safety investigation of a hydrogen fueling station with an on-site hydrogen production system involving methylcyclohexane Reviewed

    Jo Nakayama, Hitoshi Misono, Junji Sakamoto, Naoya Kasai, Tadahiro Shibutani, Atsumi Miyake

    International Journal of Hydrogen Energy   42 ( 15 )   10636 - 10644   2017.4

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    Adequate safety measures are crucial for preventing major accidents at hydrogen fueling stations. In particular, risk analysis of the domino effect at hydrogen fueling stations is essential because knock-on accidents are likely to intensify the consequences of a relatively small incident. Several risk assessment studies have focused on hydrogen fueling stations, but none have investigated accidental scenarios related to the domino effect at such stations. Therefore, the purpose of this study is to identify a domino effect scenario, analyze the scenario by using simulations and propose safety measures for preventing and mitigating of the scenario. In this hazard identification study, we identified the domino effect scenario of a hydrogen fueling station with an on-site hydrogen production system involving methylcyclohexane and investigated through simulations of the scenario. The simulations revealed that a pool fire of methylcyclohexane or toluene can damage the process equipment and that thermal radiation may cause the pressurized hydrogen tanks to rupture. The rupture-type vent system can serve as a critical safety measure for preventing and mitigating the examined scenario. (C) 2016 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

    DOI: 10.1016/j.ijhydene.2016.11.072

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  • Safety assessment of hydrogen energy carrier from a perspective of social comprehensive risk

    中山 穣, 稗貫 峻一, 坂本 惇司, 笠井 尚哉, 澁谷 忠弘, 野口 和彦, 三宅 淳巳

    水素エネルギーシステム = Journal of the Hydrogen Energy Systems Society of Japan   42 ( 3 )   138 - 144   2017

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    Language:Japanese   Publisher:水素エネルギー協会  

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  • Leakage-type-based analysis of accidents involving hydrogen fueling stations in Japan and USA Reviewed

    Junji Sakamoto, Ryunosuke Sato, Jo Nakayama, Naoya Kasai, Tadahiro Shibutani, Atsumi Miyake

    International Journal of Hydrogen Energy   41 ( 46 )   21564 - 21570   2016.12

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    To identify the safety issues associated with hydrogen fueling stations, incidents at such stations in Japan and the USA were analyzed considering the regulations in these countries. Leakage due to the damage and fracture of main bodies of apparatuses and pipes in Japan and the USA is mainly caused by design error, that is, poorly planned fatigue. Considering the present incidents in these countries, adequate consideration of the usage environment in the design is very important. Leakage from flanges, valves, and seals in Japan is mainly caused by screw joints. If welded joints are to be used in hydrogen fueling stations in Japan, strength data for welded parts should be obtained and pipe thicknesses should be reduced. Leakage due to other factors, e.g., external impact, in Japan and the USA is mainly caused by human error. To realize self-serviced hydrogen fueling stations, safety measures should be developed to prevent human error by fuel cell vehicle users. (C) 2016 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

    DOI: 10.1016/j.ijhydene.2016.08.060

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  • Preliminary hazard identification for qualitative risk assessment on a hybrid gasoline-hydrogen fueling station with an on-site hydrogen production system using organic chemical hydride Reviewed

    Jo Nakayama, Junji Sakamoto, Naoya Kasai, Tadahiro Shibutani, Atsumi Miyake

    International Journal of Hydrogen Energy   41 ( 18 )   7518 - 7525   2016.5

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    Hydrogen infrastructures are important for the commercialization of fuel cell vehicles. Hydrogen storage and transportation are significant topics because it is difficult to safely and effectively treat large amounts of hydrogen because of hydrogen hazards. An organic chemical hydride method keeps and provides hydrogen using hydrogenation and dehydrogenation chemical reactions with aromatic compounds. This method has advantages in that the conventional petrochemical products are used as a hydrogen carrier, and petrochemicals are more easily treated than hydrogen because of low hazards. Hydrogen fueling stations are also crucial infrastructures for hydrogen supply. In Japan, hybrid gasoline hydrogen fueling stations are needed for effective space utilization in urban areas. It is essential to address the safety issues of hybrid fueling stations for inherently safer station construction. We focused on a hybrid gasoline-hydrogen fueling station with an on-site hydrogen production system using methylcyclohexane as an organic chemical hydride. The purpose of this study is to reveal unique hybrid risks in the station with a hazard identification study (HAZID study). As a result of the HAZID study, we identified 314 accident scenarios involving gasoline and organic chemical hydride systems. In addition, we suggested improvement safety measures for uniquely worst-case accident scenarios to prevent and mitigate the scenarios. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.ijhydene.2016.03.143

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  • Effect of gasoline pool fire on liquid hydrogen storage tank in hybrid hydrogen-gasoline fueling station Reviewed

    Junji Sakamoto, Jo Nakayama, Toyoaki Nakarai, Naoya Kasai, Tadahiro Shibutani, Atsumi Miyake

    International Journal of Hydrogen Energy   41 ( 3 )   2096 - 2104   2016.1

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    Multiple-energy-fueling stations, which can supply several types of energy such as gasoline, CNG, and hydrogen, could guarantee the efficient use of space. To guide the safety management of hybrid hydrogen gasoline fueling stations, which utilize liquid hydrogen as an energy carrier, the scale of gasoline pool fires was estimated using the hazard assessment tool Toxic Release Analysis of Chemical Emissions (TRACE). Subsequently, the temperature and the stress due to temperature distribution were estimated using ANSYS. Based on the results, the safety of liquid hydrogen storage tanks was discussed. It was inferred that the emissivity of the outer material of the tank and the safety distance between liquid hydrogen storage tanks and gasoline dispensers should be less than 0.2 and more than 8.5 m, respectively, to protect the liquid hydrogen storage tank from the gasoline pool fire. To reduce the safety distance, several measures are required, e.g. additional thermal shields such as protective intumescent paint and water sprinkler systems and an increased slope to lead gasoline off to a safe domain away from the liquid hydrogen storage tank. Copyright (C) 2015, The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications, LLC.

    DOI: 10.1016/j.ijhydene.2015.11.039

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  • Risk assessment for a gas and liquid Hydrogen fueling station Reviewed

    Jo Nakayama, Junji Sakamoto, Naoya Kasai, Tadahiro Shibutani, Atsumi Miyake

    49th Annual Loss Prevention Symposium 2015, LPS 2015 - Topical Conference at the 2015 AIChE Spring Meeting and 11th Global Congress on Process Safety   138 - 150   2015.1

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    Hydrogen fueling stations are critical infrastructure for facilitating the commercialization of fuel cell vehicles (FCVs). In Japan, few hydrogen fueling stations have been built but several are under design or construction stages. It will be difficult to construct stand-alone hydrogen fueling stations in many locations in Japan because of the narrow spaces in urban cities. Therefore, hybrid stations with gasoline and hydrogen supply systems will be constructed to effectively use small spaces. Safety measures must be incorporated into the stations. Although stand-alone hydrogen fueling stations using compressed and liquid hydrogen have been investigated with risk assessment, the hybrid gasoline-hydrogen fueling stations have not been analyzed yet. This paper presents risk assessment from a Hazard Identification Study (HAZID) for identification of inherent accident scenarios and risks relating to gasoline and hydrogen supply systems. The study shows that HAZID was an effective assessment tool because it indicated similar accident scenarios analyzed by HAZOP and FMEA. Furthermore, HAZID revealed inherent scenarios and risks.

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  • Effect of surface flaw on fatigue strength of shot-peened medium-carbon steel Reviewed

    Junji Sakamoto, Yong-Sung Lee, Seong-Kyun Cheong

    Engineering Fracture Mechanics   133   99 - 111   2015.1

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    The effect of surface flaw on fatigue strength of shot-peened medium-carbon steel was experimentally studied. The fatigue crack initiation life, fatigue crack growth life, and fatigue limit in the steel can be increased by using shot peening (SP). The fatigue fracture of SP specimen occurred by the propagations and coalescence of fatigue cracks initiated from the initial cracks due to SP. The fatigue limit of SP specimen was determined by the propagation limit of fatigue crack. When the size of surface flaw is sufficiently small compared to the SP affected zone, the flaws have not significantly changed the fatigue strength of the SP specimens. (C) 2014 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.engfracmech.2014.11.005

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  • Effect of shot peening coverage on fatigue limit in round bar of annealed medium carbon steel Reviewed

    Junji Sakamoto, Yong-Sung Lee, Seong-Kyun Cheong

    Journal of Mechanical Science and Technology   28 ( 9 )   3555 - 3560   2014.9

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    Shot peening is an effective and economical technique for improving the fatigue strength of metallic components by inducing compressive residual stress and hardening the layer near the surface. The effect is generally evaluated by main two parameters: coverage and peening intensity. However, the valuable coverage for improving the fatigue strength depends on the shape of the target material. In this study, the effect of coverage on fatigue limit in round bar of annealed medium carbon steel was experimentally studied. The fatigue limits for shot peened round bar specimens with 140-2300% coverage increased 14-25% by comparing those for non-peened round bar specimens. The valuable range of coverage was 280-60% in the used material and shot peening condition for improving the fatigue limit in short time. The result indicates that the valuable coverage of the round bar material is higher than full coverage to improve the fatigue limit of the material due to the effect of incident angle on round bar, even though the degree depends on the materials and shot peening conditions.

    DOI: 10.1007/s12206-014-0816-9

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  • Role of eutectic silicon particles in fatigue crack initiation and propagation and fatigue strength characteristics of cast aluminum alloy A356 Reviewed

    Lei Zeng, Junji Sakamoto, Atsushi Fujii, Hiroshi Noguchi

    Engineering Fracture Mechanics   115   1 - 12   2014.1

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    The cast aluminum alloy A356 was studied to observe the effects of the eutectic silicon particles on its fatigue strength characteristics and the initiation and propagation of fatigue cracks. Two mechanisms of the initiation of the fatigue cracks were observed in the low-cycle fatigue regime, and only one in the high-cycle fatigue regime. A small fatigue life scatter was also found to be characteristics of the specimens of the alloys. Furthermore, the existence of a fatigue limit in the alloy is discussed. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.engfracmech.2013.11.016

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  • Method for Assessing Applicability of an Artificial Flaw as a Small Initial Crack for Fatigue Limit Evaluation and Its Application to a Drill Hole and an FIB Processed Sharp Notch in Annealed 0.45% Carbon Steel Reviewed

    Junji Sakamoto, Yoshimasa Takahashi, Yuuta Aono, Hiroshi Noguchi

    Journal of Testing and Evaluation   41 ( 2 )   194 - 199   2013.3

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    In this study, we propose a method for assessing the applicability of an artificial flaw as a small initial crack for fatigue limit evaluation. The proposed method is applied to drill holes and sharp notches introduced using a focused ion beam (FIB) technique in annealed 0.45% carbon steel. It is found that under rotating bending fatigue, an FIB notch can be used as a small initial crack for fatigue limit evaluation, whereas a drill hole cannot, for root area of 50 mu m. Here, root area is the square root of the area obtained by projecting the defect onto a plane perpendicular to the load axial direction. The results indicate that an FIB notch can be used as a small initial crack for fatigue limit evaluation in a greater number of materials than those in which a drill hole can be used.

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  • Small fatigue crack growth behavior from artificial notch with focused ion beam in annealed 0.45% carbon steel Reviewed

    Junji Sakamoto, Yoshimasa Takahashi, Hiroshi Noguchi

    Key Engineering Materials   488-489   319 - +   2011.9

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    The aim of this study is firstly to investigate the applicability of a sharp notch with Focused Ion Beam (FIB) as a crack for fatigue limit evaluation. Secondly we investigate a condition in which artificial defects (drilled hole, FIB notch) can be used as a crack for fatigue limit evaluation. To achieve the aim, the growth behaviors and the non-propagating crack sizes of small fatigue cracks initiated from a FIB notch and a drilled hole are carefully compared with those of an annealed fatigue crack which imitates an ideally sharp crack. The results show that a FIB notch can be used as a crack for fatigue limit evaluation under some conditions. The results also show that the condition which controls the applicability of an artificial defect as an ideal crack for fatigue limit evaluation is strongly dependent on the relation between (i) the length of a non-propagating fatigue crack and (ii) the crack length when the small fatigue crack growth behaviors from an artificial defect and an ideal pre-crack become almost the same. It is found that the length of (ii) can be obtained by the analyses using the number of cycles from a certain crack length to failure.

    DOI: 10.4028/www.scientific.net/KEM.488-489.319

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  • Effect of hydrogen on dislocation structures around a mixed-mode fatigue crack tip in a single-crystalline iron silicon alloy Reviewed

    Yoshimasa Takahashi, Junji Sakamoto, Masaki Tanaka, Kenji Higashida, Hiroshi Noguchi

    Scripta Materialia   64 ( 8 )   721 - 724   2011.4

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    The effect of hydrogen on dislocation structures around a mixed-mode fatigue crack tip in a single-crystalline iron silicon alloy was investigated by cross-sectional electron backscatter diffraction and high-voltage electron microscopy. In contrast to the previously reported results in an inert environment, no dislocation cells were formed around the crack tip in a hydrogen environment. The microscopic features around the crack tip suggest that hydrogen promotes a mode I-type crack growth mechanism, which reasonably explains the observed macroscopic crack growth property. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.scriptamat.2010.12.032

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  • Characterization of dislocation structures around a mixed-mode fatigue crack tip in a single-crystalline iron-silicon alloy Reviewed

    Yoshimasa Takahashi, Junji Sakamoto, Masaki Tanaka, Kenji Higashida, Hiroshi Noguchi

    Scripta Materialia   64 ( 2 )   157 - 160   2011.1

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    Dislocation structures around a mixed-mode fatigue crack tip introduced into a single-crystalline iron silicon alloy is characterized by cross-sectional electron backscatter diffraction and high-voltage electron microscopy. The results show that the crack growth is preceded by the formation of a cell band and the crack grows along cell boundaries. Crack growth rate and width of the cell band are constant despite the monotonic increase in stress intensity, which is anomalous in terms of the conventional fracture mechanics concept. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.scriptamat.2010.09.033

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  • TEM analysis on the effect of hydrogen on cyclic deformation around an oblique fatigue crack tip in single-crystalline Fe-3.2wt.%Si alloy Reviewed

    Yoshimasa Takahashi, Junji Sakamoto, Masaki Tanaka, Kenji Higashida, Hiroshi Noguchi

    Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A   76 ( 767 )   1002 - 1004   2010.7

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    The effect of hydrogen on local cyclic behavior around an oblique fatigue crack tip in singlecrystalline Fe-3.2wt.%Si alloy is precisely investigated by using cross-sectional transmission electron microscopy (TEM). The observation successfully reveals that the crack propagation is strongly correlated to the formation of dislocation cell structure in an inert atmosphere, whereas no cell structure is formed around the crack tip in a hydrogen atmosphere.

    DOI: 10.1299/kikaia.76.1002

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  • TEM observation of cyclic deformation around an oblique fatigue crack tip in single-crystalline fe-3.2wt.%si alloy Reviewed

    Yoshimasa Takahashi, Junji Sakamoto, Masaki Tanaka, Kenji Higashida, Hiroshi Noguchi

    Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A   76 ( 762 )   251 - 253   2010.2

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    Local cyclic slip behavior around an oblique fatigue crack tip in single-crystalline Fe-3.2 wt.% Si alloy is precisely observed by using cross-sectional transmission electron microscopy (TEM). The observation successfully reveals the existence of different dislocation structures (vein, ladder, labyrinth, cell) around the crack tip. The results clearly suggest that the crack growth is strongly related to the formation of dislocation cell structures. Additional fractographic observation suggests that the crack growth, the path of which is found to be the boundary between hard cell region and soft matrix, accompanies the formation of striation pattern along the boundary.

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  • Effect of gaseous hydrogen on cyclic slip behavior around a stage i fatigue crack tip in an iron alloy Reviewed

    Takahashi Y, Sakamoto J, Tanaka M, Higashida K, Noguchi H

    18th European Conference on Fracture: Fracture of Materials and Structures from Micro to Macro Scale   2010

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Books

  • Creep-Fatigue Fracture: Analysis of Internal Damage

    Weisheng Zhou, Naoya Tada, Junji Sakamoto

    Springer  2024.4 

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  • 水素利用技術集成 Vol.5 ~水素ステーション・設備の安全性~

    坂本惇司, 三宅淳巳( Role: Contributor ,  第3章 第7節)

    エヌ・ティー・エス  2018.12 

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  • リスク共生学 先端科学でつくる暮らしと新たな社会

    三宅淳巳, 坂本惇司( Role: Contributor ,  6.4節)

    丸善  2018.6 

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MISC

Presentations

  • Investigation on Deformation Constraint Near Fiber/Rubber Interface in Cellulose-Nanofiber-Reinforced Natural Rubber by Swelling Test

    奥井健斗, 多田直哉, 上森武, 坂本惇司, 増田廉, 榊原圭太

    日本機械学会中国四国支部総会・講演会講演論文集(CD-ROM)  2023 

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  • Study on Fatigue Damage under Bending Vibration in Aluminum Alloy

    坂本惇司, 多田直哉, 上森武

    日本材料学会学術講演会講演論文集(CD-ROM)  2023 

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  • Surface Height Change at Grain Center and Near Grain Boundaries in Pure Titanium Plate Specimen with Circular Notch under Elastic and Plastic Tensions

    緒方隆太, 多田直哉, 上森武, 坂本惇司

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2023 

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  • Changes in Crystal Orientation and Surface Height after Unloading in Stepwise Load Increasing Repeated Tensile Test of Pure Titanium Thin Sheet Specimen

    大橋弘晃, 多田直哉, 上森武, 坂本惇司

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2023 

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  • Effect of Fine Particle Peening on Bending Vibration Life of Titanium Alloy

    畑昂輝, 坂本惇司, 多田直哉, 上森武, 杉澤拓海

    日本機械学会中国四国支部総会・講演会講演論文集(CD-ROM)  2023 

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  • Predictions of active slip system in polycrystalline pure titanium thin film using crystal plasticity finite element analysis

    土居雅利, 上森武, 多田直哉, 坂本惇司

    日本機械学会中国四国支部総会・講演会講演論文集(CD-ROM)  2023 

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  • Microscopic Plastic Deformation and Fracture Processes in Smooth Specimen of Ti-6Al-4V during Tensile Test

    丸一紘大, 多田直哉, 上森武, 坂本惇司, 緒方隆太

    日本機械学会中国四国支部総会・講演会講演論文集(CD-ROM)  2023 

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  • Investigation on the Interface Bonding Strength of Fe-Al Joint Specimens Made by Forging

    両保侑希, 多田直哉, 上森武, 坂本惇司, 西本泰己, KARUNATHILAKA Nuwan

    日本機械学会中国四国支部総会・講演会講演論文集(CD-ROM)  2023 

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  • Change in bending amplitude with crack growth and its effect on crack propagation life in bending vibration of aluminum alloy

    小林大悟, 坂本惇司, 多田直哉, 上森武

    日本材料学会学術講演会講演論文集(CD-ROM)  2022 

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  • Evaluation of Early Fatigue Damage of CFRP Laminates by DC Potential Difference Method

    KOMOTO Shohei, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, NAKAMURA Shunji, SAKURAI Kaori, TAKANASHI Masahiro

    The Proceedings of Conference of Chugoku-Shikoku Branch  2022  The Japan Society of Mechanical Engineers

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  • Effect of Titanium Dioxide Particle Content on Tensile Properties of Ultra-High Molecular Weight Polyethylene/Titanium Dioxide Composites

    丸一紘大, 多田直哉, 上森武, 坂本惇司, 田中亮至

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2022 

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  • 二相組織材料に発生する不均一応力が等塑性仕事曲面に与える影響に関する均質化有限要素解析

    稲毛駿介, 上森武, 多田直哉, 坂本惇司

    塑性加工連合講演会講演論文集(CD-ROM)  2022 

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  • Slip Activation Condition for Each Crystal Grain in Thin Sheet of Polycrystalline Pure Titanium under Tension

    多田直哉, 上森武, 坂本惇司, 石丸恵太

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2022 

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  • Observation of Pull-out and Fracture Behaviour of Fibers in Cracked Specimen of Natural Rubber Reinforced with Cellulose Nanofibers during Tension

    SAKAKIBARA Momo, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, OKUI Kento, SAKAKIBARA Keita

    The Proceedings of Conference of Chugoku-Shikoku Branch  2022  The Japan Society of Mechanical Engineers

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  • Changes in Diameter and Nominal Strain of Ti-6Al-4V Alloy Thin Wire under Fatigue Loading

    TSUKIHARA Kyoka, SAKAMOTO Junji, TADA Naoya, UEMORI Takeshi, OISHI Koyo

    The Proceedings of Conference of Chugoku-Shikoku Branch  2022  The Japan Society of Mechanical Engineers

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  • Evaluation of Joint Strength between Anodized Pure Titanium and High-Density Polyethylene by Tensile Shear Tests

    KAYASHIMA Chihiro, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, MARUICHI Koudai, TANAKA Ryoji

    The Proceedings of Conference of Chugoku-Shikoku Branch  2022  The Japan Society of Mechanical Engineers

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  • Study on Tensile Deformation Behavior of Polycrystalline Pure Titanium by Microscopic Residual Strain Measurement

    MATSUMOTO Daiki, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, ISHIMARU Keita

    The Proceedings of Conference of Chugoku-Shikoku Branch  2022  The Japan Society of Mechanical Engineers

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  • Relationship between Inhomogeneous Elastic Stress Distribution and Activated Slip System in Thin Sheet Specimen of Pure Titanium during Tension

    ISHIMARU Keita, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, MATSUMOTO Daiki

    The Proceedings of Conference of Chugoku-Shikoku Branch  2022  The Japan Society of Mechanical Engineers

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  • Effect of Cyclic Bending Deformation on Tensile Strength of Aluminum Foil

    田辺太一, 多田直哉, 上森武, 坂本惇司, 白神修

    日本材料学会学術講演会講演論文集(CD-ROM)  2021.5.30 

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  • Observation of slip lines of pure titanium thin wire in stepwise tensile test

    坂本惇司, 島田侑紀, 多田直哉, 上森武

    日本材料学会学術講演会講演論文集(CD-ROM)  2021.5.29 

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  • Study on slip deformation behavior of crystal grains in notched thin sheet specimens of pure titanium during tension

    ISHIDA Takashi, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, ISHIMARU Keita

    The Proceedings of Conference of Chugoku-Shikoku Branch  2021  The Japan Society of Mechanical Engineers

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  • Numerical Investigation on Rolling Texture of Aluminum by Crystal Plasticity Theory

    TANABE Takuya, UEMORI Takeshi, TADA Naoya, SAKAMOTO Junji, MITSUI Kousuke, ONODERA Kouki

    The Proceedings of Conference of Chugoku-Shikoku Branch  2021  The Japan Society of Mechanical Engineers

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  • Analytical Study on Evaluation of Bauschinger Effect of Aluminum Sheet by L-bending Test

    NISHIYAMA Daigo, UEMORI Takeshi, TADA Naoya, SAKAMOTO Junji

    The Proceedings of Conference of Chugoku-Shikoku Branch  2021  The Japan Society of Mechanical Engineers

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  • 面内反転時の6056アルミニウム合金の応力-ひずみ応答に関する解析的検討

    酒匂麻帆, 上森武, 多田直哉, 坂本惇司

    日本金属学会講演大会(Web)  2021 

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  • アルミニウム合金の温間二軸引張変形挙動の解析的検討

    村尾侑亮, 上森武, 多田直哉, 坂本惇司

    日本金属学会講演大会(Web)  2021 

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  • リーン型二相ステンレス鋼板の二軸応力状態下における塑性変形挙動の実験的検討

    藤田隼輔, 上森武, 多田直哉, 坂本惇司, 石丸詠一朗

    塑性加工連合講演会講演論文集  2020.11.14 

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  • Crystal plastic homogenization finite element analysis of Ti-6242 alloy subjected to in-plane reverse loading

    MITSUI Kousuke, UEMORI Takeshi, TADA Naoya, SAKAMOTO Junji

    The Proceedings of Mechanical Engineering Congress, Japan  2020.9.14  The Japan Society of Mechanical Engineers

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    Event date: 2020.9.13 - 2020.9.16

    Language:Japanese   Presentation type:Oral presentation (general)  

    <p>To investigate effects of dislocation density on microscopic stress distribution and macroscopic stress-strain relation, we conducted crystal plastic homogenization finite element analysis of Ti-6242 alloy subjected to in-plane reverse loading with dislocation density calculation. As a result, Statistically Stored (SS) dislocation density increased with occurrence of slip deformation for all conditions. On the other hand, Geometrically Necessary (GN) dislocation density was less likely to accumulate at the interface in the parallel relationship between primary slip systems of hcp and bcc. Although GN dislocations only develop near the interface, a large increase in GN dislocation density affects the macroscopic stress-strain relation.</p>

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  • Evaluation of Stress Reversal Deformation Behavior of 590 MPa High Tensile Strength Steel Sheet by Using L-Bending Analysis

    上森武, 多田直哉, 坂本惇司, 中本浩聖, 西山大悟, 松村宗一郎, 成田忍

    日本材料学会学術講演会講演論文集  2020.5 

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  • Evaluation of Tensile and Bending Damages of CFRP Laminates by DC Potential Difference Method

    SATO Kazuma, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, KOMOTO Shohei, SUZUKI Natsumi, TAKANASHI Masahiro

    The Proceedings of Conference of Chugoku-Shikoku Branch  2020.3  The Japan Society of Mechanical Engineers

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  • Experimental study on strength differential effect of stainless steel sheet

    柴井宏治, 上森武, 多田直哉, 坂本惇司

    材料とプロセス(CD-ROM)  2020.3 

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  • Effect of resin film lamination on tensile deformation characteristics of stainless steel foil

    信定宥杜, 多田直哉, 坂本惇司, 上森武

    材料とプロセス(CD-ROM)  2020.3 

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  • Numerical analysis for inhomogeneous compressive deformation of Multi-Layered Ceramic Capacitor block

    TAMAO Seijiro, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji

    The Proceedings of Conference of Chugoku-Shikoku Branch  2020.3  The Japan Society of Mechanical Engineers

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  • Surface height change during tensile deformation of natural rubber reinforced with cellulose nanofibers.

    榊原桃, 多田直哉, 上森武, 坂本惇司, 石田諭史, 岩本伸一朗

    日本機械学会年次大会講演論文集(CD-ROM)  2020 

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  • Evaluation of Fatigue Characteristics of Ti-6Al-4V Alloy Thin Wire

    築原京香, 坂本惇司, 多田直哉, 上森武, 島田侑紀

    日本機械学会年次大会講演論文集(CD-ROM)  2020 

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  • Evaluation of Joint Strength between Pure Titanium with Different Surface Properties and High-Density Polyethylene by Tensile Shear Test

    萱嶋千紘, 多田直哉, 上森武, 坂本惇司, 西川紘平

    日本機械学会年次大会講演論文集(CD-ROM)  2020 

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  • Analysis of Relationship between Potential Difference and Fiber Distribution inside CFRP Focusing on the Current Path

    河本詳平, 多田直哉, 上森武, 坂本惇司

    日本機械学会年次大会講演論文集(CD-ROM)  2020 

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  • Study on the Relationship between Surface Roughness, Residual Stress, and Fatigue Life of High Speed Tool Steel with Precision Shot Peening and Polishing

    川西志朗, 多田直哉, 上森武, 坂本惇司, KARUNATHILAKA Nuwan

    日本機械学会年次大会講演論文集(CD-ROM)  2020 

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  • Fatigue strength evaluation of aluminum alloy under multiaxial random vibration

    SAKAMOTO Junji, YAMADA Tomoka, TADA Naoya, UEMORI Takeshi, SHIBUTANI Tadahiro

    The Proceedings of the Materials and Mechanics Conference  2019.11.4  The Japan Society of Mechanical Engineers

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    Event date: 2019.11.2 - 2019.11.4

    Language:Japanese   Presentation type:Oral presentation (general)  

    <p>Various mechanical components are subjected to random multiaxial vibration. For their safe and effective operation, it is essential to precisely evaluate the fatigue strength of the materials under multiaxial random vibration. However, the mechanisms and evaluation methods remain unclear. In this study, we performed the multiaxial random vibration experiments using aluminum alloy A5056 specimens in order to discuss a method for evaluating the vibration fatigue strength of materials. The multiaxial random vibration experiments were conducted at an acceleration input of 70 Grms within a frequency band of 10–5000 Hz under a nitrogen gas environment at a room temperature. During the multiaxial random vibration experiments the strains of the specimen were measured using 3-axis and 1-axis strain gauges and the maximum principal strains and their directions of a fracture part were estimated. Based on the results, the method for evaluating the vibration fatigue strength of materials was discussed.</p>

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  • オーステナイト系ステンレス鋼XM-19の疲労強度と破面解析

    坂本惇司, 山本翔太, 澁谷忠弘, 志賀優多, 竹花立美, 佐野尊

    構造物の安全性および信頼性(CD-ROM)  2019.10 

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  • Study on Defect Detection Method using Surface Height Change due to Low Loading

    SAKAMOTO Junji, KUNIYASU Hayato, TADA Naoya, UEMORI Takeshi

    The Proceedings of Mechanical Engineering Congress, Japan  2019.9.9  The Japan Society of Mechanical Engineers

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    Event date: 2019.9.8 - 2019.9.11

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  • Study on Application of Direct-Current Potential Difference Method to Fatigue of Titanium Alloy Thin Wire

    TADA Naoya, TAKAGI Yusuke, SHIMADA Yuki, UEMORI Takeshi, SAKAMOTO Junji

    The Proceedings of Mechanical Engineering Congress, Japan  2019.9.9  The Japan Society of Mechanical Engineers

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    Event date: 2019.9.8 - 2019.9.11

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  • Experimental observations of cyclic plastic deformation behaviors of 590MPa class high tensile strength steel sheet and its modeling

    UEMORI Takeshi, NAKAMOTO Hiromasa, TADA Naoya, SAKAMOTO Junji

    The Proceedings of Mechanical Engineering Congress, Japan  2019.9.9  The Japan Society of Mechanical Engineers

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    Event date: 2019.9.8 - 2019.9.11

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  • Applying a comprehensive societal risk framework to hydrogen fueling stations

    Atsumi Miyake, Junji Sakamoto, Shunichi Hienuki, Jo Nakayama, Yu Ichiro Izato, Kazuhiko Noguchi

    Global Congress on Process Safety 2018, GCPS 2018 - Topical Conference at the 2018 AIChE Spring Meeting and 14th Global Congress on Process Safety  2018 

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    Event date: 2018

    Language:English  

    © GCPS 2018.All right reserved. New perspectives on a comprehensive societal risk framework for technological systems are introduced and discussed in relation to an example application involving a hydrogen fueling station for fuel cell vehicles. The comprehensive societal risk framework consists of not only technological and economic risks, but also environmental and societal risks. This framework will be indispensable to risk communication efforts and initiatives to foster the public acceptance of technological systems.

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  • 590MPa級DP鋼の繰返し引張‐圧縮試験とその構成モデル

    中本浩聖, 上森武, 多田直哉, 坂本惇司, 早川邦夫

    材料とプロセス(CD-ROM)  2019.8.26 

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  • 引張せん断試験によるアルミニウム合金/高密度ポリエチレンの接合強度評価

    多田直哉, 阿部俊太朗, 上森武, 坂本惇司

    日本材料学会学術講演会講演論文集  2019.5.24 

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  • 多軸ランダム振動下のアルミニウム合金の応力場とそれに及ぼすショットピーニングの影響

    坂本惇司

    日本材料学会学術講演会講演論文集  2019.5.24 

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  • 多結晶純チタンの引張りにおける結晶方位変化を考慮に入れた微視的すべり変形の評価

    佐藤宏樹, 多田直哉, 上森武, 坂本惇司

    日本金属学会講演概要(CD-ROM)  2019.3.6 

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  • 高張力鋼板の面内繰返し応力‐ひずみ応答に与えるひずみ速度の影響

    上森武, 多田直哉, 坂本惇司, 中本浩聖, 早川邦夫

    材料とプロセス(CD-ROM)  2019.3.1 

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  • 精密ショットピーニング処理と研磨を施した高速度工具鋼の疲労寿命

    花光崚太, KARUNATHILAKA Nuwan, 多田直哉, 上森武, 坂本惇司

    日本機械学会中国四国支部総会・講演会講演論文集(CD-ROM)  2019 

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  • リスク共生設計の提案:極限環境試験を用いた機器の故障モード特定による機器設計

    坂本惇司, 澁谷忠弘, 伊里友一朗, 野口和彦, 中山穣, 三宅淳巳

    安全工学シンポジウム講演予稿集  2018.7.3 

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  • 多軸ランダム振動下のアルミニウム合金の疲労破壊挙動

    坂本惇司, 澁谷忠弘

    日本材料学会学術講演会講演論文集  2018.5.25 

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  • Qualitative evaluation of hydrogen station with HAZID study

    KASAI Naoya, NAKAYAMA Jo, SAKAMOTO Junji, SHIBUTANI Tadahiro, MIYAKE Atsumi

    The Proceedings of Mechanical Engineering Congress, Japan  2017.9.5 

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  • Modeling of a hydrogen fueling station using physical modeling and quantitative estimation of hydrogen release based on accident scenarios

    SAKAMOTO Junji, MISONO Hitoshi, NAKAYAMA Jo, KASAI Naoya, SHIBUTANI Tadahiro, MIYAKE Atsumi

    The Proceedings of Mechanical Engineering Congress, Japan  2017.9.5 

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  • 微小傷から発生したき裂の応力場に及ぼす傷形状および微視組織の影響の有限要素解析

    坂本惇司, 澁谷忠弘

    日本機械学会年次大会講演論文集(CD-ROM)  2016.9.10 

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  • 水素スタンドにおける継手からの水素漏洩の検討

    佐藤龍之介, 中山穣, 坂本惇司, 笠井尚哉, 澁谷忠弘, 三宅淳巳

    日本機械学会年次大会講演論文集(CD-ROM)  2016.9.10 

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  • 多結晶体モデルにおける仮想的なマルテンサイト変態導入の検討

    山本翔太, 坂本惇司, 澁谷忠弘

    日本機械学会年次大会講演論文集(CD-ROM)  2016.9.10 

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  • 物理モデリングを用いた水素ステーションにおける緊急時の水素放散法の評価

    彌園仁志, 坂本惇司, 中山穣, 笠井尚哉, 澁谷忠弘, 三宅淳巳

    日本機械学会年次大会講演論文集(CD-ROM)  2016.9.10 

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  • Analysis of Peeling Behavior and Thermal Stress in Adhesion Strength Test of High Temperature Mold Resin

    平田 諒磨, 澁谷 忠弘, 坂本 惇司

    マイクロエレクトロニクスシンポジウム論文集  2016.9.8 

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  • 有機ハイドライド型水素ステーションにおける蓄圧器に及ぼすプール火災の影響

    中山穣, 彌園仁志, 坂本惇司, 半井豊明, 笠井尚哉, 澁谷忠弘, 三宅淳巳

    日本火災学会研究発表会概要集  2016.5.11 

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  • 液化水素型水素スタンド併設給油取扱所に関するHAZID Studyを用いたSafety Critical Elementsの抽出

    中山穣, 坂本惇司, 笠井尚哉, 澁谷忠弘, 三宅淳巳

    安全工学研究発表会講演予稿集  2015.12.3 

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  • CNGスタンドにおけるディスペンサー周辺の防爆エリアに関する検討

    塩田謙人, 中山穣, 坂本惇司, 熊崎美枝子, 笠井尚哉, 澁谷忠弘, 三宅淳巳

    安全工学研究発表会講演予稿集  2015.12.3 

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  • スズおよびスズ銅合金における結晶異方性に基づく熱応力の有限要素解析

    坂本惇司, 大原久和, 澁谷忠弘

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2015.11.20 

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  • 液化水素型水素スタンド併設給油取扱所におけるガソリン火災時の液化水素貯槽に及ぼす輻射熱の影響

    坂本惇司, 中山穣, 半井豊明, 笠井尚哉, 澁谷忠弘, 三宅淳巳

    日本機械学会年次大会講演論文集(CD-ROM)  2015.9.12 

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  • 液化水素型水素スタンド併設給油取扱所におけるHAZID解析とETAを用いた損傷発生確率の検討

    佐藤龍之介, 中山穣, 坂本惇司, 笠井尚哉, 澁谷忠弘, 三宅淳巳

    日本機械学会年次大会講演論文集(CD-ROM)  2015.9.12 

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  • S45C焼入れ焼戻し材を用いた欠陥形状が疲労き裂の停留挙動に及ぼす影響の検討

    HAMANO YASUAKI, ZAIZEN KENGO, MATSUEDA TAKAHIRO, SAKAMOTO JUNJI, HAMADA SHIGERU, NOGUCHI HIROSHI

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2013.10.10 

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  • Applicability of a FIB-notch as a small initial crack for fatigue limit evaluation

    Sakamoto J, Takahashi Y, Noguchi H

    19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012  2012.1.1 

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    In this study, we propose a method for assessing the applicability of an artificial defect as a small initial crack for fatigue limit evaluation. The proposed method is applied to drill holes and sharp notches introduced using a focused ion beam (FIB) technique in annealed 0.45% carbon steel. It is found that under rotating bending fatigue, an FIB notch can be used as a small initial crack for fatigue limit evaluation, whereas a drill hole cannot, for of ∼50 μm. Here, is the square root of the area obtained by projecting the defect onto a plane perpendicular to the load axial direction. The results indicate that an FIB notch can be used as a small initial crack for fatigue limit evaluation in a greater number of materials than those in which a drill hole can be used.

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    Other Link: http://orcid.org/0000-0002-2108-2258

  • FIB加工による人工欠陥を有するS45C焼鈍し材の微小疲労き裂進展挙動

    坂本惇司, 高橋可昌, 野口博司

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2011 

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  • Effect of gaseous hydrogen on cyclic slip behavior around a stage i fatigue crack tip in an iron alloy

    Takahashi Y, Sakamoto J, Tanaka M, Higashida K, Noguchi H

    18th European Conference on Fracture: Fracture of Materials and Structures from Micro to Macro Scale  2010.12.1 

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    In order to investigate the effect of gaseous hydrogen on cyclic slip behavior around an early stage (stage Ifatigue crack tip, fatigue crack growth (FCGtests using a single-crystalline Fe-3.2wt.%Si alloy are conducted respectively in a hydrogen atmosphere and in a helium atmosphere. The cross-sectional observations of the crack tips by both electron backscatter diffraction (EBSDmethod and transmission electron microscopy (TEMsuccessfully reveal the following points. In helium atmosphere, FCG is preceded by formation of cell structures and crack propagates along cell boundaries. In hydrogen atmosphere, on the other hand, no cells are seen, and crack growth process is similar to that observed in a stage II type FCG. Crack extension resistance in hydrogen is postulated to be lower than that in helium, indicating that the mode of FCG in hydrogen is more critical than that in helium.

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    Other Link: http://orcid.org/0000-0002-2108-2258

  • 透過型電子顕微鏡による傾斜疲労き裂先端の微視的すべり挙動におよぼす水素の影響解析

    坂本惇司, 高橋可昌, 田中將己, 東田賢二, 野口博司

    日本材料学会学術講演会講演論文集  2010.5.21 

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  • Optimization of Shape of Stress-relief Groove for Improvement of Fretting Fatigue Strength

    SAKAMOTO JUNJI, KONDO YOSHIYUKI, KUBOTA MASANOBU

    日本機械学会年次大会講演論文集  2009.9.12 

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Research Projects

  • 材料損傷による振動モード変化を応用した非破壊検査・長寿命化手法の開発

    Grant number:24K07235  2024.04 - 2028.03

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    坂本 惇司

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    Grant amount:\4550000 ( Direct expense: \3500000 、 Indirect expense:\1050000 )

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  • Prediction of deformation localization and fracture in polycrystalline titanium alloy based on 3D measurement of ultra-small inhomogeneous deformation

    Grant number:21H01214  2021.04 - 2024.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    多田 直哉, 上森 武, 坂本 惇司

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    Grant amount:\17810000 ( Direct expense: \13700000 、 Indirect expense:\4110000 )

    研究の初年度に当たる本年度では,3D測定レーザー顕微鏡を導入し,試験片表面における微小な変形を測定する準備をするとともに,純チタン試験片の引張に関して,既存の走査型電子顕微鏡およびデジタルホログラフィック顕微鏡も併用して試験片表面の観察を行った.本研究では,試験片に小さな引張負荷を段階的にかけながら結晶方位や応力分布を測定する薄膜試験片を用いた試験と,段階的に引張荷重をかけながら,各引張荷重を除荷した後に残留応力を測定する試験の2種類の試験を実施した.いずれも結晶粒にすべり線が発生するまで試験を実施し,微視的変形レベルにおいて弾性変形と塑性変形の関係について検討した.まず,前者の試験では,引張負荷によって生じる各結晶粒のすべりは,試験片が完全な弾性変形段階にあると見なせる小さな負荷において測定される各結晶粒の応力分布および想定されるすべり系に関するせん断応力成分と,そのすべり系の臨界分解せん断応力を用いることによりかなり高い確率で予想できることが明らかとなった.また,後者の試験からは,除荷後の各結晶粒の残留応力分布から計算できる活動すべり系のせん断応力の勾配が,発生したすべり線の方向に近い傾向にあることが明らかになった.再現性と理由については,今後,検討する予定である.
    結晶塑性有限要素法に関しては,多結晶体モデルを作成するプログラムを導入し,少結晶粒モデルに関しては解析が可能であるとの感触を得た.結晶粒数や要素分割に関する検討にはさらに時間を要すると考えられる.

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  • ネッキング型破壊の抑制とコーキシング効果の応用による微小金属材料の耐疲労特性向上方法の開発

    2021.04 - 2022.03

    公益財団法人JKA  2021年度機械振興補助事業 個別研究 

    坂本 惇司

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  • Investigation of vibration fatigue crack growth behavior and vibration fatigue strength improvement by peening

    Grant number:20K14610  2020.04 - 2023.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists  Grant-in-Aid for Early-Career Scientists

    坂本 惇司

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    Grant amount:\4160000 ( Direct expense: \3200000 、 Indirect expense:\960000 )

    本研究では,①振動疲労き裂進展時のき裂先端近傍の力学場の状態とそれがき裂進展とともにどう変化するのかを明らかにすること,および,②ピーニングによる振動時の疲労強度向上技術を構築することを目的とする.それぞれの目的に対して,本年度に推進した主な実施内容を以下に示す.
    <BR>
    ①試験片切欠き部の表面と裏面にひずみゲージを貼付し,試験片の表面と裏面のひずみを測定することで,振動試験時のマクロな力学状態を検討した.その結果,曲げ振動試験においては,純粋な曲げに加えて遠心力による引張が加わるが,今回の試験片においては,遠心力による引張ひずみは,曲げで付与される最大引張ひずみに比べて無視できる程度であることが分かった.また,昨年度に確認された疲労損傷とともに振動モード(曲げ振幅)が変化する現象について,高速度カメラを用いた観察,ひずみゲージによる破断部近傍のひずみの測定,プラスチックレプリカ法を用いたき裂進展挙動の観察を行うことで検討した.その結果,疲労損傷とともに試験片がわずかに伸びることおよび疲労き裂が進展することにより,固有振動数が変化することが考えられた.
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    ②振動疲労強度を向上させるピーニング手法として,本年度はニードルピーニングを検討した.その結果,振動疲労寿命をわずかに増加させる可能性はあるものの,顕著な変化は確認できなかった.その原因として,圧縮残留応力の付与や硬さの向上等の疲労寿命を向上させる影響と,表面粗さの増加等の疲労寿命を低下させる影響が同程度であるためだと考えられる.そのため,次年度は,微粒子ピーニングを用いてピーニングの影響について検討する予定である.

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  • 繰返し硬さ試験による疲労寿命の簡易評価法の確立とその微小材料の疲労寿命の向上探索への応用

    2019.04 - 2020.03

    公益財団法人村田学術振興財団  研究助成 

    坂本 惇司

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    Authorship:Principal investigator  Grant type:Competitive

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  • Prediction of Development of Inhomogeneous Plastic Deformation and Fracture Based on Change in Elastic Height Distribution in Polycrystalline Metals

    Grant number:18H01337  2018.04 - 2021.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    Tada Naoya

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    Grant amount:\17940000 ( Direct expense: \13800000 、 Indirect expense:\4140000 )

    Tensile tests were carried out using plate and thin sheet specimens of polycrystalline pure titanium. Microscopic inhomogeneous deformations under elastic and plastic conditions were discussed focusing on the deformation of thin sheet specimens where the effect of interior crystal grains was week. The following resutls were obtained. Height changes at the center of grains were correlated with those near the grain boundaries. Correlation between the height changes on the front and back surfaces changed when the deformation changed from elastic to plastic. The initiation of slip lines near the notch could be predicted by slip activity.

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  • 振動疲労強度におけるショットピーニングによる表面塑性加工の効果の検討

    2017.10 - 2019.03

    公益財団法人天田財団  奨励研究助成B(萌芽的研究) 

    坂本 惇司

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    Authorship:Principal investigator  Grant type:Competitive

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  • Mechanism of fatigue damage of materials under six-axial random vibration and evaluation testing method

    Grant number:17K14556  2017.04 - 2020.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)  Grant-in-Aid for Young Scientists (B)

    Sakamoto Junji

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\4420000 ( Direct expense: \3400000 、 Indirect expense:\1020000 )

    We investigated a fatigue fracture of a material subjected to multi-axis random vibration which complicatedly changes the amplitude and direction. In the case of a material with a simple shape, the material could vibrate in a resonance mode. Therefore, there is a possibility that the fatigue strength can be evaluated using the stress in the direction with the largest load. In the case of a material with a complicated shape, the material could vibrate in a few resonance modes. Therefore, there is a possibility that the fatigue strength cannot be evaluated using only the stress in the direction of the largest load. The evaluated fatigue strength might be higher than the actual fatigue strength.

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