Koike, Ryo

写真a

Affiliation

Faculty of Science and Technology, Department of System Design Engineering （Yagami）

Position

Associate Professor
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Papers 【 Display / hide 】

  • Mechanical property evaluation of the SLM support structure and lattice structure of SUS316L

    Ikeda Y., Okochi W., Koike R., Maki T., Takaki K., Mori T., Hirono Y., Kakinuma Y.

    Journal of Advanced Mechanical Design, Systems and Manufacturing （Journal of Advanced Mechanical Design, Systems and Manufacturing)  17 （ 1 ）  2023

    　View Summary

    Selective laser melting (SLM) is one of the additive manufacturing (AM) methods which is applicable to metal. This technique makes it possible to form complex internal shapes such as lattice structures. The lattice structure is expected to have weight reduction and vibration suppression effects on the product. In addition, a support structure is essential for the SLM fabrication process, which has the role of supporting the product and dissipating heat from the product. However, steep temperature gradients due to local laser irradiation and non-uniform heat conduction during the process can cause bending and cracking of the product. In particular, the support structure and lattice structure consisting of thin metal struts are greatly affected by process conditions, so it is necessary to select conditions suitable for stable and high-precision modeling. In this study, the influence of laser power and scanning speed on the mechanical characteristics of the support structure and lattice structure formed by SLM is investigated. In the tensile test of the support structure, a positive correlation with the volumetric energy density was confirmed, and suitable laser conditions were examined. In the compression test of the lattice structure, it was clear that the amount of energy absorption changed depending on the laser power, and the condition of 240 W achieved the maximum energy absorption.

  • Evaluation of fabrication parameters for foam stainless steel in directed energy deposition

    Ikeda Y., Takeuchi T., Koike R., Kakinuma Y., Kondo M., Oda Y., Mori T.

    Journal of Advanced Mechanical Design, Systems and Manufacturing （Journal of Advanced Mechanical Design, Systems and Manufacturing)  17 （ 1 ）  2023

    　View Summary

    Directed energy deposition (DED), a metal additive manufacturing process, has attracted considerable attention in various industries. In the past few decades, several studies have been conducted to enhance the quality of DED-produced parts. Various studies on powder- and laser-based DED have focused on eliminating the residual pores in the fabricated parts, which decrease the mechanical strength. In contrast, this study aims at intentionally increasing the residual pores to produce a porous structure in metals called as foam metal, which realizes lightweight and excellent energy absorption properties. Despite being well-known for their attractive properties, Foam metals are rarely used due to the technical difficulties in their production, which requires special devices and entails considerable cost. The simplicity of the DED process makes it a promising approach to fabricate foam metals because it is easy to foam at the fabrication point by mixing a foaming agent, such as titanium hydride (TiH2), into the material powder. This study evaluates the DED foaming process in stainless steel alloys by changing the particle size of the TiH2 powder and the scanning path to obtain the optimal conditions for enhancing the pore dispersion. The experimental results show that, when the particle size of the foaming agent is small, the number of pores and their distribution increases. Additionally, the mechanical properties are also evaluated through compression experiments, and the energy absorption ratio is found to be higher when a smaller foaming agent is used.

  • Basic study for lunar regolith powder bed fusion in high gravity

    Koike R., AlKhaled A., Kashimoto T.

    CIRP Annals （CIRP Annals)   2023

    ISSN  00078506

    　View Summary

    In-situ resource utilization has become a significant issue in recent space projects. For example, various studies have focused on lunar manufacturing using regoliths available on the moon's surface. Although regolith manufacturing will be conducted under lunar gravity, most studies have not considered the adverse effects of low gravity on additive manufacturing processes. This study evaluates the gravitational effect on lunar regolith powder bed fusion (PBF) by applying centrifugal acceleration to the PBF process. The experimental results show that gravitational acceleration influences the density, hardness, and transparency of the fabricated regolith blocks.

  • Optimization of process parameters for hardness in high speed coating by Directed Energy Deposition

    Satoh T., Koike R., Kakinuma Y., Hirono Y., Mori T., Oda Y.

    Procedia CIRP （Procedia CIRP)  111   214 - 217 2022

    ISSN  22128271

    　View Summary

    In recent years, metal 3D printers have been attracting attention not only for building solid parts but also for repairing and coating processes. The goal of this study is to apply the directed energy deposition (DED), which is one of the additive manufacturing, to realize high-quality metal coating by depositing the coating material on a cylindrical object. To evaluate the effect of process parameters, experimental points were set up based on the central composite design and deposition was performed using Inconel 625 as the material powder. The hardness of the coating was measured and statistically analyzed by the response surface methodology. From the analysis results, it was found that laser power has the largest influence on the coating hardness, which was improved by 28% compared to the low rotation speed by depositing under the optimum processing parameters.

  • Enhancement in fine powder availability for Powder Bed Fusion applying high gravity

    Obe K., Koike R.

    Procedia CIRP （Procedia CIRP)  111   121 - 124 2022

    ISSN  22128271

    　View Summary

    In recent years, additive manufacturing (AM) technology that can directly shape objects from three-dimensional data has attractedattention.AM technology is promising as a manufacturing method in space because of its resource and space-saving properties. Some studies have shown that gravity change is viewed as a problem to overcome. On the other hand, there has been no progress in the discussion of attempts to effectively utilize gravity changes for AM technology. In this study, we focus on powder bed fusion (PBF) among AM technologies, using gravity as a control factor. The high gravity PBF (HG-PBF) is expected to be able to solve the problems of the current AM technology such as improvement of shape accuracy and process stability. In this study, we used fine powders and experimentally discuss the effect of the high gravity field on improvement of PBF process.

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Papers, etc., Registered in KOARA 【 Display / hide 】

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

  • Low-density foam metal fabrication based on net-zero gravity process

    2022.04
    -
    2025.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, 基盤研究(B), Principal investigator

  • Metal 3D printing by powder bed fusion applying artificial gravity control

    2019.04
    -
    2022.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists , Principal investigator

  • Development of direct deposition for porous structure based on molten-metal dynamics analysis with particle method

    2017.04
    -
    2019.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Young Scientists (B), Principal investigator

  • 合金固液相変化を解析する指向性エネルギー堆積法シミュレータの開発

    2016.08
    -
    2018.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Research Activity Start-up , Principal investigator

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Courses Taught 【 Display / hide 】

  • SEMINAR IN SYSTEM DESIGN ENGINEERING

    2024

  • MACHINE DESIGN

    2024

  • LABORATORIES IN SYSTEM DESIGN ENGINEERING 2)

    2024

  • LABORATORIES IN SCIENCE AND TECHNOLOGY

    2024

  • INTRODUCTION TO SYSTEM DESIGN ENGINEERING

    2024

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