Japanese Society of Tribologists Acta Medica Okayama 1881-2198 20 4 2025 Tribological Properties of Amorphous-SiC-Based Coatings on Al2O3 Substrates in Normal Saline 212 219 EN Tadashi Shiota Faculty of Environmental, Life, Natural Science and Technology, Okayama University Daiki Taniya Graduate School of Natural Science and Technology, Okayama University Kazuma Shimazaki Graduate School of Natural Science and Technology, Okayama University Chiyu Nakano Department of Comprehensive Technical Solutions, Okayama University Yuya Omiya Faculty of Environmental, Life, Natural Science and Technology, Okayama University Masahiro Fujii Faculty of Environmental, Life, Natural Science and Technology, Okayama University Amorphous SiC (a-SiC)-based coatings containing not only Si–C bonds but also C–Si–O, C–C, and Si–O2 bonds were deposited on Al2O3 substrates via pulsed laser deposition. Sliding tests using SiC ceramic balls in normal saline revealed that the coating exhibited a low friction coefficient of 0.05-0.06 at a shorter running-in process than SiC bulk ceramic plates. The specific wear rate of the coating was also lower than that of the SiC plate. Reactive molecular dynamics simulations revealed that the C–Si–O bonds in the coating facilitated the generation of Si–O units, which contained Si–O bonds but no Si-C bonds, through tribochemical reactions with water, resulting in superior tribological properties in normal saline compared to those of SiC plates. These findings demonstrate that a-SiC-based coatings containing C–Si–O bonds are promising as low-friction and low-wear coatings for biomedical implants such as ceramic joint prostheses. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0301-679X 214 2026 The influence of lubricant additives and surface roughness and hardness of material on the damage behavior of gears 111341 EN Takuya Ohno Faculty of Environmental, Life, Natural Science and Technology, Okayama University Tadashi Shiota Faculty of Environmental, Life, Natural Science and Technology, Okayama University Masahiro Fujii Faculty of Environmental, Life, Natural Science and Technology, Okayama University This study investigates the influence of lubricant additives, surface roughness, and material hardness on gear damage behavior under boundary lubrication conditions. We conducted both the Short-term Test and the Standard Test using an FZG gear test machine to evaluate how lubricant additives and gear surface roughness influence damage progression when the surface roughness exceeds the oil-film thickness. Acid phosphate ester effectively suppressed micropitting through surface smoothing but led to severe damage such as pitting and scuffing during prolonged use. In contrast, sulfurized fatty oil promoted mild wear, delaying catastrophic failures and extending gear life. Higher surface roughness accelerated wear, while increased hardness reduced deformation but it expanded damage areas. The study found that initial surface roughness and its progress during load stages strongly correlate with gear durability. Measurement of arithmetic mean roughness after sufficient running-in under actual load conditions proved useful for predicting long-term performance. These findings highlight the importance of selecting lubricant formulations tailored to specific gear operating environments and damage modes. Understanding the interplay between lubrication chemistry and material properties enables the design of more durable gear systems. No potential conflict of interest relevant to this article was reported.

Japanese Society of Tribologists Acta Medica Okayama 1881-2198 20 3 2025 Water Lubrication of Polysiloxane-Containing Polyimide Coatings on Stainless Steel Substrates 124 129 EN Yuelin Fan Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Tadashi Shiota Faculty of Environmental, Life, Natural Science and Technology, Okayama University Yuya Omiya Faculty of Environmental, Life, Natural Science and Technology, Okayama University Masahiro Fujii Faculty of Environmental, Life, Natural Science and Technology, Okayama University This study investigated the water-lubricated tribological properties of coatings made of a novel polysiloxane-containing polyimide (si-PI) material that was recently developed for the aerospace industry and can be diluted with the harmless and environmentally friendly ethanol or water. The si-PI coatings were deposited on stainless steel (JIS SUS304) substrates at curing temperatures ranging from 160°C to 275°C. Their water lubrication properties were measured by rubbing the coatings against each other in water at room temperature. The coatings exhibited lower friction than conventional polyimide materials, with a minimum friction coefficient of 0.04, which was lower than that of polytetrafluoroethylene (PTFE) measured under the same sliding conditions. Unlike the conventional polyimide, the coatings did not exhibit any obvious wear or damage. The results demonstrate that the si-PI coating is a promising low-friction and highly durable coating for water lubrication. No potential conflict of interest relevant to this article was reported.

Public Library Science Acta Medica Okayama 1932-6203 17 9 2022 Prevention of non-infectious pulmonary complications after intra-bone marrow stem cell transplantation in mice e0273749 EN Yoshiko Yamasuji-Maeda Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Hisakazu Nishimori Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Keisuke Seike Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Akira Yamamoto Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Hideaki Fujiwara Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Taiga Kuroi Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kyosuke Saeki Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Haruko Fujinaga Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Sachiyo Okamoto Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Ken-Ichi Matsuoka Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Nobuharu Fujii Department of Transfusion Medicine, Okayama University Hospital Takehiro Tanaka Department of Pathology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Masahiro Fujii Department of Animal Resources, Advanced Science Research Center, Okayama University Katsumi Mominoki Department of Animal Resources, Advanced Science Research Center, Okayama University Takuro Kanekura Department of Dermatology, Kagoshima University Graduate School of Medical and Dental Sciences Yoshinobu Maeda Department of Hematology and Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Non-infectious pulmonary complications including idiopathic pneumonia syndrome (IPS) and bronchiolitis obliterans syndrome (BOS), which are clinical and diagnostic manifestations of lung chronic graft-versus-host disease (GVHD), cause significant mortality after allogeneic stem cell transplantation (SCT). Increasing evidence suggests that alloantigen reactions in lung tissue play a central role in the pathogenesis of IPS and BOS; however, the mechanism is not fully understood. Several clinical and experimental studies have reported that intrabone marrow (IBM)-SCT provides high rates of engraftment and is associated with a low incidence of acute GVHD. In the present study, allogeneic SCT was conducted in mouse models of IPS and BOS, to compare intravenous (IV)-SCT with IBM-SCT. Allogeneic IBM-SCT improved the clinical and pathological outcomes of pulmonary complications compared to those of IV-SCT. The mechanisms underlying the reductions in pulmonary complications in IBM-SCT mice were explored. The infiltrating lung cells were mainly CD11b+ myeloid and CD3+ T cells, in the same proportions as in transplanted donor cells. In an in vivo bioluminescence imaging, a higher proportion of injected donor cells was detected in the lung during the early phase (1 h after IV-SCT) than after IBM-SCT (16.7 +/- 1.1 vs. 3.1 +/- 0.7 x 10(5) photons/s/animal, IV-SCT vs. IBM-SCT, P = 1.90 x 10(-10)). In the late phase (5 days) after SCT, there were also significantly more donor cells in the lung after IV-SCT than after IBM-SCT or allogeneic-SCT (508.5 +/- 66.1 vs. 160.1 +/- 61.9 x 10(6) photons/s/animal, IV-SCT vs. IBM-SCT, P = 0.001), suggesting that the allogeneic reaction induces sustained donor cell infiltration in the lung during the late phase. These results demonstrated that IBM-SCT is capable of reducing injected donor cells in the lung; IBM-SCT decreases donor cell infiltration. IBM-SCT therefore represents a promising transplantation strategy for reducing pulmonary complications, by suppressing the first step in the pathophysiology of chronic GVHD. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2075-4701 9 7 2019 Effect of Lubrication and Forging Load on Surface Roughness, Residual Stress, and Deformation of Cold Forging Tools 783 EN Nuwan Karunathilaka Graduate School of Natural Science and Technology, Okayama University Naoya Tada Graduate School of Natural Science and Technology, Okayama University Takeshi Uemori Graduate School of Natural Science and Technology, Okayama University Ryota Hanamitsu Graduate School of Natural Science and Technology, Okayama University Masahiro Fujii Graduate School of Natural Science and Technology, Okayama University Yuya Omiya Graduate School of Natural Science and Technology, Okayama University Masahiro Kawano Zeno Tech Co., Ltd Cold forging is a metal forming that which uses localized compressive force at room temperature. During the cold forging process, the tool is subjected to extremely high loads and abrasive wear. Lubrication plays an important role in cold forging to improve product quality and tool life by preventing direct metallic contact. Surface roughness and residual stress also greatly affects the service life of a tool. In this study, variations in surface roughness, residual stress, and specimen deformation with the number of cold forging cycles were investigated under different forging conditions. Specimens that were made of heat-treated SKH51 (59-61 HRC), a high-speed tool steel with a polished working surface, were used. The specimens were subjected to an upsetting process. Compressive residual stress, surface roughness, and specimen deformation showed a positive relationship with the number of forging cycles up to a certain limit and became almost constant in most of the forging conditions. A larger change in residual stress and surface roughness was observed at the center of the specimens in all the forging conditions. The effect of the magnitude of the forging load on the above discussed parameters is large when compared to the effect of the lubrication conditions. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 24 1 1989 Effects of Drive System Lubricant Additives upon Rolling Fatigue of Carburized and Hardened Steel Rollers 1 12 EN Akira Yoshida Yuji Ohue Masahiro Fujii 10.18926/15466 To clarify the effects of a drive system lubricant additive upon rolling fatigue of rollers manufactured from carburized and hardened steel, three types of oil were used as lubricants: one mineral base oil and the other two mineral base oils to which an S-P additive package and ATF additive package were added, respectively. These specimens were tested for sliding/rolling fatigue and examined for failure on the surface, rolling fatigue strength, and other properties. Roller surface temperatures and inter-roller frictional coefficients were found scarcely affected by the type of oil used. Irrespective of the difference in oil type, failure on the surface was found to be entirely spalling attributable to cracks generated in the subsurface. The depth at which spalling cracks had taken place was found nearly coincident with the depth at which a ratio of reversing orthogonal shear stress to hardness had amplitude A(Tyz/Hv) maximized. These depths were larger as Hertz stress became more prominent. Nevertheless, they were found hardly affected by the type of oil. Although rolling fatigue strength did not show a significant difference dependent upon the type of oil, it may be said that fatigue life would be somewhat negatively affected by an extreme pressure coated film with a content of sulfur and phosphorus. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 39 1 2005 Improving Methods of Wear Resistance in Heavy Loaded SlidingFriction Pairs 1 6 EN Masahiro Fujii Akira Yoshida 10.18926/14134 Improvement of wear resistance and durability of machine elements with sliding friction pairs is the important tribological problems. The wear resistance has been determined with many configurative parameters, technological parameters, and operational parameters. In this study kinematics of cylindrical joint (CJ), whose motion is reciprocating and rotating, and influence of various parameters on wear resistance of friction pair was investigated. No potential conflict of interest relevant to this article was reported.