Details of a Researcher - Komotori, Jun

Papers - Komotori, Jun

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Effect of Tensile Loading on the Residual Stress Relaxation Behavior of Induction Hardened SCM440 Steel with a Shallow Hardened Layer,

T. Aoki, M. Hayama, S. Takesue, A. Ezura, M.Tsukahara, Y.Misaka, S.Kikuchi, J.Komotori

ISIJ International 65 ( 2 ) 308 - 314 2025

Last author, Corresponding author, Accepted

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Regulating Cell Orientation Using a Femtosecond Laser-Induced Macro Stripe Design on Metallic Culture Surfaces with Laser-Treated and Mirrored Areas

C. Imashiro, A.Ezura, Takahiro G.Yamada, Y.Akiyama, J.Komotori

Advanced Biomedical Engineering 14 ( 2 ) 126 - 133 2025

Last author, Corresponding author, Accepted

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Estimation of residual stress relaxation in low alloy steel with different hardness during fatigue by in situ X-ray measurement

Hayama: M., Kikuchi S., Tsukahara M., Misaka Y., Komotori J.

International Journal of Fatigue (International Journal of Fatigue) 178 2024.01

ISSN 01421123

In situ X-ray stress measurements were conducted to investigate the relaxation of compressive residual stress induced by fine particle peening during fatigue. To quantitatively assess the stability of the compressive residual stress, a concept of relaxation threshold stress was proposed. The relaxation threshold stress, which indicates the stability of the compressive residual stress, showed a direct correlation with specimen hardness. If the combined value of the compressive residual stress and compressive applied stress surpass the relaxation threshold stress, then the compressive residual stress relaxes. The relaxation threshold stress can be used to estimate the relaxation that occurs during fatigue.

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Change Behavior of Retained Austenite and Residual Stress on Carburized SCM420H Steel during Fatigue Process

M. Hayama, Y. Maki, S. Kikuchi, J. Komotori

ISIJ International 64 ( 3 ) 597 - 604 2024

Accepted

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Estimation of residual stress relaxation in low alloy steel with different hardness during fatigue by in situ X-ray measurement,

M．Hayama, S. Kikuchi, M. Tsukahara, Y. Misaka, J.Komotori,

International Journal of Fatigue 178 2024

Accepted

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Effect of surface characteristics on the axial fatigue properties and wear resistance of Ti-6Al-4V alloy nitrided by gas blow induction-heating

S. Takesue, R. Suyama, M. Hayama, Y. Koyanagi, Y. Misaka, J. Komotori

Engineering Failure Analysis (Engineering Failure Analysis) 157 ( 107933 ) 2024

Accepted, ISSN 13506307

The effects of surface characteristics on the axial fatigue properties and wear resistance of the GBIH-nitrided titanium alloy were investigated to improve the fatigue strength and wear resistance of Ti-6Al-4V alloy rapidly nitrided by induction-heating in a nitrogen atmosphere with blowing nitrogen gas (GBIH-nitriding). The fatigue strength of the GBIH-nitrided Ti-6Al-4V alloy was lower than that of the mirror-polished specimen owing to the formation of a brittle nitrogen compound layer and grain coarsening. Fatigue tests using specimens prepared by combining GBIH-nitriding and particle collision treatments revealed that the formation of nitrogen diffusion layers at the outermost surface and the generation of compressive residual stress without forming surface asperities increased the fatigue strength of the GBIH-nitrided Ti-6Al-4V alloy. Moreover, the formation of a nitrided layer and suppression of surface asperities effectively improved the wear resistance of the Ti-6Al-4V alloy. Therefore, formation of a nitrogen diffusion layer and the introduction of compressive residual stress without grain coarsening, a compound layer, and surface asperities increased the fatigue strength and wear resistance of the GBIH-nitrided alloy.

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浅い表面焼入れ層を有するSCM440鋼の残留応力解放挙動に及ぼす引張負荷の影響

青木智史，羽山元晶，武末翔吾，江面篤志，塚原真宏，三阪佳孝，菊池将一，小茂鳥潤

鉄と鋼 110 ( 14 ) 1142 - 1149 2024

Accepted, ISSN 00211575

Fatigue tests under axial loading were conducted on steel with a shallow hardened layer induced by induction hardening, and in situ X-ray stress measurements were performed to investigate the relaxation of residual stresses during fatigue. The residual stresses were relaxed owing to tensile loading and not compressive loading. The two conditions that bring about this phenomenon are (i) a high peak of tensile residual stress just below the hardened layer, and (ii) the hardened layer coinciding with the compressive residual stress field that prevents the yielding of the compressive residual stress field under compressive loading. In this case, tensile yielding occurred just below the hardened layer under tensile loading, the residual stresses are redistributed, and the compressive residual stress on the material surface is relaxed. The experimental results also showed that the fatigue fracture morphology changed depending on the residual stress relaxation behavior.

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Rapid carburizing of low-alloy steel by atmospheric-controlled induction-heating fine-particle peening and investigation of its fatigue properties

Takesue S., Kasai D., Aoki T., Tsukahara M., Misaka Y., Komotori J.

Journal of Materials Research and Technology 33 2244 - 2251 2024

ISSN 22387854

Atmospheric-controlled induction-heating fine-particle peening (AIH-FPP) was applied to low-alloy, low-carbon steel AISI 4120 to achieve rapid carburizing within minutes and enhance fatigue strength. The shot particles used during AIH-FPP were specifically created by mechanically milling a mixture of steel particles and carbon powders. The specimens were analyzed using laser microscopy, optical microscopy, X-ray diffraction for residual stress measurement, a micro-Vickers hardness tester, and an electron probe micro-analyzer. Axial fatigue tests and fracture surface analyses via scanning electron microscopy and energy-dispersive X-ray spectroscopy were also conducted. AIH-FPP effectively transferred carbon to the treated surface and facilitated its diffusion in a short period, creating a martensite layer with high hardness and compressive residual stress, which resulted in increased fatigue strength. The fatigue strength of the AIH-FPP-treated specimens was influenced by the conditions of reheating and quenching, which altered the prior austenitic grain size and stress concentration at the specimen surface. Notably, specimens treated with AIH-FPP followed by reheating and water-injection quenching exhibited fatigue strength comparable to that of conventional gas-carburized specimens, owing to the formation of a carburized layer with a small prior austenite grain size.

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Rapid carburizing of low-alloy steel by atmospheric-controlled induction-heating fine particle peening and investigation of its fatigue properties

S. Takesue, D. Kasai, T. Aoki, M. Tsukahara, Y. Misaka, J. Komotori,

Journal of Materials Research and Technology 33 2244 - 2251 2024

Accepted

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Development of AIH-FPP carburizing process using carbon powder

[1] G. Umeno, M. Hayama, S. Takesue, T. Tomita, T. Kato, Y. Misaka, J. Komotori

Materials Transactions 64 ( 2 ) 617 - 625 2023.01

Accepted

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Rapid formation of titanium nitride coating by atmospheric-controlled induction-heating fine particle peening and investigation of its wear and corrosion resistance

S．Takesue, T．Morita, Y．Misaka, J．Komotori

Results in Surfaces and Interfaces (Results in Surfaces and Interfaces) 11 2023

Accepted

To create a coating of titanium nitride, atmospheric-controlled induction-heating fine particle peening using fine particles of pure titanium was conducted for low-alloy steel in a nitrogen atmosphere, and the surface characteristics of the treated specimens were investigated. The formation of hard titanium nitride coatings with a thickness of 100–200 μm was achieved by peening at 1373 K for 10 s and subsequent heating at 1373 K for 120 s. Titanium particles adhered to the treated surfaces during peening at the high temperature, which reacted with nitrogen in the atmosphere during the heating after peening. Ball-on-disk wear tests were conducted to examine the wear resistance of the specimens, and it was found that the created coating by AIH-FPP improved the wear resistance of low-alloy steel owing to its high hardness. The improvement was more significant at high testing temperatures because the high testing temperature and frictional heat caused oxygen in the air to react with titanium in the coating during the wear test. Immersion of the specimens into sodium chloride solution was also conducted to investigate the corrosion resistance, which revealed that the coating created improved corrosion resistance of low-alloy steel.

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Metallic Vessel with Mesh Culture Surface Fabricated Using Three-dimensional Printing Engineers Tissue Culture Environment

Imashiro C., Morikura T., Hayama M., Ezura A., Komotori J., Miyata S., Sakaguchi K., Shimizu T.

Biotechnology and Bioprocess Engineering (Biotechnology and Bioprocess Engineering) 28 ( 1 ) 181 - 191 2023

ISSN 12268372

Various culture devices have been developed as fundamental technologies for facilitating bioengineering studies. Culture devices are designed to prepare specific culture environments. Thus, both macrostructures and surface micromorphology should be considered in the device design. Although fabricating devices with elaborate designs incurs high production costs, disposable materials are typically used for culture devices. However, some metallic materials are strong, stable, and biocompatible. Bioengineers have not applied these materials to culture devices because of the difficulty of processing. An emerging technology using three-dimensional (3D) printing has been developed, which can produce complex designs using metal. We demonstrate the applicability and potential of metal 3D printing for fabricating culture devices toward the development of the bioengineering discipline. As a specific example, we fabricated metallic culture devices where the environment of cultured tissues can be improved. One of the biggest factors determining the culture environment is active media supply. To attain active media supply to the tissue, devices having culture surfaces with mesh structures having holes far larger than cells were proposed. Cell sheets were cultured as tissue models, realizing tissue culture with such structures. The cultured tissue showed increased metabolism, indicating enhanced media supply owing to mesh surfaces. The biocompatibility of the 3D printed metal device was confirmed by viability assays on cultured cells, and reusability of the device was confirmed by mechanical and biochemical evaluations. We believe this study serves as a reference for using metallic 3D printing as an option for fabricating culture devices, which will promote bioengineering research.

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Titanium Culture Vessel Presenting Temperature Gradation for the Thermotolerance Estimation of Cells

Imashiro C., Jin Y., Hayama M., Yamada T.G., Funahashi A., Sakaguchi K., Umezu S., Komotori J.

Cyborg and Bionic Systems (Cyborg and Bionic Systems) 4 2023

ISSN 20971087

Hyperthermia can be induced to exploit the thermal intolerance of cancer cells, which is worse than that of normal cells, as a potential noninvasive cancer treatment. To develop an effective hyperthermia treatment, thermal cytotoxicity of cells should be comprehensively investigated. However, to conduct such investigations, the culture temperature must be accurately regulated. We previously reported a culture system in which the culture temperature could be accurately regulated by employing metallic culture vessels. However, appropriate temperature conditions for hyperthermia depend on the cell species. Consequently, several experiments need to be conducted, which is a bottleneck of inducing hyperthermia. Hence, we developed a cell culture system with temperature gradation on a metallic culture surface. Michigan Cancer Foundation-7 cells and normal human dermal fibroblasts were used as cancer and normal cell models, respectively. Normal cells showed stronger thermal tolerance; this was because the novel system immediately exhibited a temperature gradation. Thus, the developed culture system can be used to investigate the optimum thermal conditions for effective hyperthermia treatment. Furthermore, as the reactions of cultured cells can be effectively assessed with the present results, further research involving the thermal stimulation of cells is possible.

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炭素粉末を用いたAIH-FPP浸炭プロセスの開発

梅野玄, 羽山元晶, 武末翔吾, 富田翼, 加藤健郎, 三阪佳孝, 小茂鳥潤,

材料 71 ( 9 ) 787 - 794 2022.09

Accepted

Evaluation of the compressive residual stress relaxation behavior by in situ X-ray stress measurement

M. Hayama, S. Kikuchi, J.Komotori

ISIJ International 62 ( 4 ) 758 - 765 2022.04

Titanium Culture Vessel Capable of Controlling Culture Temperature for Evaluation of Cell Thermotolerance

C.Imashiro, Y.Ida, S.Miyata, J.Komotori,

Materials Transactions (Materials Transactions) 63 ( 633 ) 373 - 378 2022.03

ISSN 13459678

Surgery, radiation therapy, and chemical therapy have been reported as the main treatments for cancer, which is one of the deadliest reported diseases. However, because of the high invasiveness of patients, cancer hyperthermia has been studied as a non-invasive treatment. Hyperthermia uses a difference in thermal tolerance between normal and cancer cells and provides an affected part thermal stimulation to kill cancer cells selectively. To develop effective conditions for hyperthermia, an in vitro study to evaluate the thermal tolerance is required. However, because the existing cell culture vessels cannot control the culture temperature, genuine thermal tolerance of cells cannot be investigated appropriately. To reveal the critical temperature proper for hyperthermia, we developed a culture device controlling culture temperature. With the developed device, culture temperature was regulated considerably more quickly than the conventional method with the existing vessels, which enabled us to study the thermal tolerance of cells appropriately. For the control of culture temperature, the device has a titanium culture substrate, where a Peltier element is adhered. Because the biocompatibility of the device was confirmed, the difference in thermal tolerance between normal and cancer cells was investigated using the developed device as well as normal human dermal fibroblasts and Michigan Cancer Foundation-7 as model cell species. Therefore, it was confirmed that cancer cells were more sensitive to thermal stimulation than normal cells, which was qualitatively consistent with previous studies. Thus, our developed device can be used to investigate the thermal tolerance of each cell species, which will contribute to the development of cancer hyperthermia.

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Effect of room temperature fine particle peening pretreatment on grain refinement of Fe-Cr alloys by AIH-FPP

S. Takesue, S. Kikuchi, J.Komotori

Materials Transactions 63 ( 2 ) 203 - 208 2022

Accepted

Surface modification of titanium alloy via atmospheric pressure nitrogen plasma assisted femtosecond laser irradiation

Katahira K., Ezura A., Takesue S., Komotori J.

CIRP Annals (CIRP Annals) 2022

ISSN 00078506

The effect of atmospheric pressure nitrogen plasma in conjunction with femtosecond laser surface modification of Ti–6Al–4V samples was investigated. It was suggested that the superior friction and wear characteristics of the LP series (the sample subjected to both laser and plasma irradiation) were induced by the synergistic combination of the following three factors: the increased smoothness induced by homogenizing the laser-induced periodic surface groove shape structure, the high hardness caused by grain refinement and the high toughness and low friction properties conferred to the sample by the formation of oxynitride.

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Effect of atmospheric-controlled induction-heating fine particle peening on microstructure and fatigue properties of low-alloy steel

Takesue S., Hayama M., Komotori J.

Fatigue and Fracture of Engineering Materials and Structures (Fatigue and Fracture of Engineering Materials and Structures) 45 ( 10 ) 2908 - 2919 2022

Accepted, ISSN 8756758X

Atmospheric-controlled induction-heating fine particle peening (AIH-FPP) was performed for low-alloy steel, and the effects of the peening temperature, the microstructure of steel, and thermal history during AIH-FPP on the resultant microstructure of treated steel were investigated. Regardless of the prior microstructure and thermal history, the grains near the surfaces were refined by AIH-FPP at peening temperatures from 923 K to 1023 K owing to dynamic recrystallization. To examine the effect of AIH-FPP on the fatigue properties of steel, plane-bending fatigue tests were performed. Compared with the steel mirror-polished, treated with FPP at RT, or only induction-heated, the fatigue properties of steel treated with AIH-FPP were improved. This is because of the formation of a thick and uniform grain-refined layer, the generation of compressive residual stress, and hardening of the surface by AIH-FPP. Moreover, owing to the grain refinement progress, the fatigue properties of steel improved with increasing peening temperature.

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Development of AIH-FPP Carburizing Process Using Carbon Powder

Umeno G., Hayama M., Takesue S., Tomita T., Kato T., Misaka Y., Komotori J.

Zairyo/Journal of the Society of Materials Science, Japan (Zairyo/Journal of the Society of Materials Science, Japan) 71 ( 9 ) 787 - 794 2022

ISSN 05145163

In this study, the surface of industrial pure iron was treated with atmospheric-controlled induction heating fine particle peening (AIH-FPP) using mechanical coating (MC) particles of carbon/steel obtained by mixing carbon powder and fine steel particles using mechanical milling. The surface modification effect and the mechanism of its effect were examined and considered by analyzing of the treated surface. Results showed that a modified layer in which carbon elements were diffused was formed near the treated surface by the AIH-FPP treatment using MC particles. In addition, by examining the influence of the treatment conditions on the formation of the modified layer by the design of experiments, the treatment temperature showed the most significant influence among the treatment temperature, peening time, and gas flow rate. The higher the treatment temperature, the deeper the carbon diffused layer. In addition, when treated at ≥1273 K, the microstructure near the surface became pearlite, and Vickers hardness increased. The time required for carbon diffusion in the AIH-FPP carburizing process using MC particles of carbon/steel was approximately the same as that of a general carburizing treatment using a reactive gas. In the AIH-FPP carburizing process, carbon is considered to be transferred from the particles to the surface, and the grain boundaries and dislocations increased by fine particle preening (FPP) are used as channels to diffuse inside the specimen. This mechanism is entirely different from the conventional carburizing methods.

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