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Papers by Takeshi Kunishima

A manufacturing method of a bar component (221) including a pipe (10) made of a carbon fiber rein... more A manufacturing method of a bar component (221) including a pipe (10) made of a carbon fiber reinforced resin and an internal metal member (16) having an outer peripheral surface (16A) in contact with an inner peripheral surface (10C) of an end portion of the pipe (10) in an axial direction (X) is provided. The method includes: preparing a core including a metal mandrel extending in the axial direction (X) and the internal metal member (16) having the outer peripheral surface (16A) subjected to surface roughening process; winding a prepreg sheet (26) obtained by impregnating carbon fibers with resin around an outer peripheral surface of the core; forming the pipe (10) having the end portion fitted onto and fixed to the outer peripheral surface (16A) of the internal metal member (16) by baking and curing the prepreg sheet (26) wound around the outer peripheral surface of the core; and removing the mandrel from the pipe (10).

(LTDS) kindly offered me much support for optical microscope observations and interferometry meas... more (LTDS) kindly offered me much support for optical microscope observations and interferometry measurements. I would also like to express my gratitude to all colleagues outside our research team in the laboratory for their kind help. I would like to acknowledge Associate Prof. Clotilde Minfray (LTDS, Ecole Central de Lyon). Her remarkable experience in the field of tribochemistry provided me insights into my results. Dr. Jules Galipaud (LTDS) provided me with a high level of technical support in the XPS analysis to detect tribofilm formation. They kindly took part in the co-authoring of my paper, and without their special knowledge, which is dedicated to tribochemistry, the value of my research work would not be so great. Ms. Sophie Pavan (LTDS) kindly offered her help with the micro-indentation measurements. Mr. Didier Roux (LTDS) kindly machined my testing samples many times. Dr. Julien Fontaine (LTDS) kindly visited my company in Japan to discuss and allowed me to attend the ElyT workshop. Ms. Hélène Schoch (LTDS) kindly helped me to manage administrative tasks. In addition, I would like to express my gratitude to Mr. Laurent Dupuy and Ms. Delphine Pavon in SCIENCE ET SURFACE who kindly conducted the ToF-SIMS analysis. Their knowledge was truly helpful for the clarification of tribochemistry on the sliding surface. Without significant help from my colleagues in material research development in JTEKT Corporation, I would not have completed my PhD work with high quality. Mr. Yasuharu Nagai (JTEKT) had technical discussions with me on the tribology of composite and polymer gear many times, and he took part in the co-authoring of several of my papers. Mr. Koji Kimura (JTEKT) gave me much support in the preparation of test samples through his professional technique of twin-screw extrusion and injection molding. Mr. Kazuki Nobetani (JTEKT), Mr. Junya Matsuyama (JTEKT), and Ms. Ayumi Odagiri (my former colleague in JTEKT) cooperated with me in the preparation and evaluation of test samples and for the chemical analysis. Mr. Toshiyuki Baba (JTEKT) also gave me technical advice based on his career in research on fiber-reinforced composites and chemical analysis. I would like to thank all of the extraordinary members of my research group (group 1 in the Organic Material Laboratory). In addition, Mr. Kazunori Miyake (group manager in Group 2 in the Organic Material Laboratory at JTEKT) and Ms. Kanako Takahara (JTEKT) frequently spared time and kindly gave me much helpful technical advice on the grease and tribology of polymers. Mr. Chikara Nakajima (JTEKT) helped me with the optical microscope observation of the metallic structure and provided me with knowledge of the heat treatment of steel. Dr. Masahiro Suzuki (General Manager in the Tribology Laboratory at JTEKT) gave me useful feedback on the results of tribochemistry, which was based on his professional experience as a PhD researcher in the field of tribology. Mr. Kazuhisa Kitamura (Group Manager in the Analysis and Evaluation Group at JTEKT) kindly hosted the luncheon meeting at WTC Beijing in 2017 when we first met Prof. Philippe Kapsa and Prof. Vincent Fridrici. Mr. Katsuhiko Kizawa (General Manager in Material Research Development in JTEKT) gave me insightful findings not only on the knowledge of material research, which is based on his career as a researcher of steel material and heat treatment technology, but also on several non-scientific topics (geopolitics, management, etc.) based on his special experience in the USA. I would like to express my greatest appreciation to the PhD students at LTDS. Despite being far away from my country, I could keep up my mental stability and motivation with the assistance of many associates. I was fortunate to have such good LTDS mates. In particular, Mr. Tadashi Oshio gave me useful advice as a PhD student from a Japanese company, which was the same scenario I was in. I would also like to express my gratitude to his family. Dr. Yuta Muramoto also gave me great advice on my PhD study and French life, including the French language, as a preceding PhD candidate in the same research group. Dr. Haohao Ding also gave me some advice as a preceding PhD candidate in the same research group, and his PhD thesis with great quality inspired me to improve my own. Ms. Vilayvone Saisnith frequently came to talk to me as a PhD student in the same research group and kindly offered me great assistance when I had difficulty with French. In addition, I would like to express my gratitude to all my LTDS colleagues, including Mr.

Tribology International, 2021

Abstract In this study, the influence of temperature on the tribological properties of unreinforc... more Abstract In this study, the influence of temperature on the tribological properties of unreinforced or glass-fiber reinforced PA66 in contact with carbon steel under boundary lubrication with grease was studied when considering the temperature dependence of the mechanical properties on the sliding surface of PA66 and the tribochemical reaction to zinc carboxylate additives in grease. XPS and ToF-SIMS analyses revealed the formation of a carboxylate tribofilm on the steel surface and a zinc sulfide reactive film on the PA66 surface, which are related to the tribochemical reaction of the additives present in the grease applied. The formation of the tribofilm contributed to an improvement of the tribological properties, particularly at 80 °C.

Wear, 2020

Abstract Polyamide 66 is widely used for sliding parts that are in contact with steel under greas... more Abstract Polyamide 66 is widely used for sliding parts that are in contact with steel under grease lubrication, including worm gears or bearing retainers. To meet the requirements for downsizing these parts and for their use under severe conditions, reinforcement fibers, such as glass fibers, are added to polyamide 66 to increase its strength and stiffness. However, the use of glass-fiber-reinforced polyamide 66 composites in sliding parts leads to wear and creep of the composites due to peeling of the fibers and scratching of polyamide 66 during sliding. Additionally, the aggressive effects of the hard fibers on the steel counterpart should be considered. In this study, the effects of the composition of glass-fiber-reinforced polyamide 66 on its tribological properties were investigated to aid in the development of a composite with optimal tribological properties. The results indicate that the use of higher-molecular-mass polyamide 66, smaller-diameter glass fibers, and a suitable glass fiber treatment agent to improve the interfacial adhesion of the fibers to polyamide 66 can enhance the wear and creep resistance of the composite and decrease the aggressive effect of the glass fibers on the steel counterpart, which occurs via two-body abrasive wear.

Wear, 2020

Abstract Polyamide 66 is widely used for sliding parts, such as resin worm gear. Glass fibers are... more Abstract Polyamide 66 is widely used for sliding parts, such as resin worm gear. Glass fibers are usually added to increase its strength. In this study, the tribological behavior of glass fiber reinforced-polyamide 66 composite in contact with carbon steel under high contact pressure, sliding, and grease lubricated conditions is studied. Measurement of mechanical properties and SEM observations of composite sliding surfaces after different sliding cycle numbers indicate that sliding induces characteristic damage of the surface (peeled off fibers and scratching of polyamide) and a degradation in mechanical properties. These lead to an increase in friction and creep of the composite. The wear effect increases with the increase in sliding cycles, and the initial orientation of the fibers in the composite sliding surface has significant effects on the wear of the steel counterpart. The contribution of each phenomenon to the tribological behavior is discussed. The damage to the composite surface and the increase in contact temperature due to sliding have great effects on the tribological properties compared to the presence of wear debris in grease and wear on the steel. The effects of the hardness of the steel on the tribological properties are investigated, and it is found that wear of the composite is reduced by using softer steels.

Materials & Design, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Polyamide 66 is widely used in polymer sliding parts including polymer gear. These parts are used... more Polyamide 66 is widely used in polymer sliding parts including polymer gear. These parts are used under lubrication of oil and grease. In this study, the friction mechanism of the contact between polyamide 66 and a steel counterpart lubricated with additive-free polyalphaolefin8 oil was discussed by focusing on various parameters including the sliding surface roughness, normal load (contact pressure), sliding speed, temperature, and hardness of the steel counterpart. To explain the friction coefficient obtained under different test conditions, the theoretical minimum oil film thickness was calculated using the equation of the soft elastic hydrodynamic lubrication regime presented by Hamrock and Dowson considering the temperature dependence of oil viscosity and polymer mechanical properties, and the master curve of the relationship between Λ and the friction coefficient was proposed considering the change in the roughness on the sliding surface. In addition, the contributions of the ...

A manufacturing method of a bar component (221) including a pipe (10) made of a carbon fiber rein... more A manufacturing method of a bar component (221) including a pipe (10) made of a carbon fiber reinforced resin and an internal metal member (16) having an outer peripheral surface (16A) in contact with an inner peripheral surface (10C) of an end portion of the pipe (10) in an axial direction (X) is provided. The method includes: preparing a core including a metal mandrel extending in the axial direction (X) and the internal metal member (16) having the outer peripheral surface (16A) subjected to surface roughening process; winding a prepreg sheet (26) obtained by impregnating carbon fibers with resin around an outer peripheral surface of the core; forming the pipe (10) having the end portion fitted onto and fixed to the outer peripheral surface (16A) of the internal metal member (16) by baking and curing the prepreg sheet (26) wound around the outer peripheral surface of the core; and removing the mandrel from the pipe (10).

(LTDS) kindly offered me much support for optical microscope observations and interferometry meas... more (LTDS) kindly offered me much support for optical microscope observations and interferometry measurements. I would also like to express my gratitude to all colleagues outside our research team in the laboratory for their kind help. I would like to acknowledge Associate Prof. Clotilde Minfray (LTDS, Ecole Central de Lyon). Her remarkable experience in the field of tribochemistry provided me insights into my results. Dr. Jules Galipaud (LTDS) provided me with a high level of technical support in the XPS analysis to detect tribofilm formation. They kindly took part in the co-authoring of my paper, and without their special knowledge, which is dedicated to tribochemistry, the value of my research work would not be so great. Ms. Sophie Pavan (LTDS) kindly offered her help with the micro-indentation measurements. Mr. Didier Roux (LTDS) kindly machined my testing samples many times. Dr. Julien Fontaine (LTDS) kindly visited my company in Japan to discuss and allowed me to attend the ElyT workshop. Ms. Hélène Schoch (LTDS) kindly helped me to manage administrative tasks. In addition, I would like to express my gratitude to Mr. Laurent Dupuy and Ms. Delphine Pavon in SCIENCE ET SURFACE who kindly conducted the ToF-SIMS analysis. Their knowledge was truly helpful for the clarification of tribochemistry on the sliding surface. Without significant help from my colleagues in material research development in JTEKT Corporation, I would not have completed my PhD work with high quality. Mr. Yasuharu Nagai (JTEKT) had technical discussions with me on the tribology of composite and polymer gear many times, and he took part in the co-authoring of several of my papers. Mr. Koji Kimura (JTEKT) gave me much support in the preparation of test samples through his professional technique of twin-screw extrusion and injection molding. Mr. Kazuki Nobetani (JTEKT), Mr. Junya Matsuyama (JTEKT), and Ms. Ayumi Odagiri (my former colleague in JTEKT) cooperated with me in the preparation and evaluation of test samples and for the chemical analysis. Mr. Toshiyuki Baba (JTEKT) also gave me technical advice based on his career in research on fiber-reinforced composites and chemical analysis. I would like to thank all of the extraordinary members of my research group (group 1 in the Organic Material Laboratory). In addition, Mr. Kazunori Miyake (group manager in Group 2 in the Organic Material Laboratory at JTEKT) and Ms. Kanako Takahara (JTEKT) frequently spared time and kindly gave me much helpful technical advice on the grease and tribology of polymers. Mr. Chikara Nakajima (JTEKT) helped me with the optical microscope observation of the metallic structure and provided me with knowledge of the heat treatment of steel. Dr. Masahiro Suzuki (General Manager in the Tribology Laboratory at JTEKT) gave me useful feedback on the results of tribochemistry, which was based on his professional experience as a PhD researcher in the field of tribology. Mr. Kazuhisa Kitamura (Group Manager in the Analysis and Evaluation Group at JTEKT) kindly hosted the luncheon meeting at WTC Beijing in 2017 when we first met Prof. Philippe Kapsa and Prof. Vincent Fridrici. Mr. Katsuhiko Kizawa (General Manager in Material Research Development in JTEKT) gave me insightful findings not only on the knowledge of material research, which is based on his career as a researcher of steel material and heat treatment technology, but also on several non-scientific topics (geopolitics, management, etc.) based on his special experience in the USA. I would like to express my greatest appreciation to the PhD students at LTDS. Despite being far away from my country, I could keep up my mental stability and motivation with the assistance of many associates. I was fortunate to have such good LTDS mates. In particular, Mr. Tadashi Oshio gave me useful advice as a PhD student from a Japanese company, which was the same scenario I was in. I would also like to express my gratitude to his family. Dr. Yuta Muramoto also gave me great advice on my PhD study and French life, including the French language, as a preceding PhD candidate in the same research group. Dr. Haohao Ding also gave me some advice as a preceding PhD candidate in the same research group, and his PhD thesis with great quality inspired me to improve my own. Ms. Vilayvone Saisnith frequently came to talk to me as a PhD student in the same research group and kindly offered me great assistance when I had difficulty with French. In addition, I would like to express my gratitude to all my LTDS colleagues, including Mr.

Tribology International, 2021

Abstract In this study, the influence of temperature on the tribological properties of unreinforc... more Abstract In this study, the influence of temperature on the tribological properties of unreinforced or glass-fiber reinforced PA66 in contact with carbon steel under boundary lubrication with grease was studied when considering the temperature dependence of the mechanical properties on the sliding surface of PA66 and the tribochemical reaction to zinc carboxylate additives in grease. XPS and ToF-SIMS analyses revealed the formation of a carboxylate tribofilm on the steel surface and a zinc sulfide reactive film on the PA66 surface, which are related to the tribochemical reaction of the additives present in the grease applied. The formation of the tribofilm contributed to an improvement of the tribological properties, particularly at 80 °C.

Wear, 2020

Abstract Polyamide 66 is widely used for sliding parts that are in contact with steel under greas... more Abstract Polyamide 66 is widely used for sliding parts that are in contact with steel under grease lubrication, including worm gears or bearing retainers. To meet the requirements for downsizing these parts and for their use under severe conditions, reinforcement fibers, such as glass fibers, are added to polyamide 66 to increase its strength and stiffness. However, the use of glass-fiber-reinforced polyamide 66 composites in sliding parts leads to wear and creep of the composites due to peeling of the fibers and scratching of polyamide 66 during sliding. Additionally, the aggressive effects of the hard fibers on the steel counterpart should be considered. In this study, the effects of the composition of glass-fiber-reinforced polyamide 66 on its tribological properties were investigated to aid in the development of a composite with optimal tribological properties. The results indicate that the use of higher-molecular-mass polyamide 66, smaller-diameter glass fibers, and a suitable glass fiber treatment agent to improve the interfacial adhesion of the fibers to polyamide 66 can enhance the wear and creep resistance of the composite and decrease the aggressive effect of the glass fibers on the steel counterpart, which occurs via two-body abrasive wear.

Wear, 2020

Abstract Polyamide 66 is widely used for sliding parts, such as resin worm gear. Glass fibers are... more Abstract Polyamide 66 is widely used for sliding parts, such as resin worm gear. Glass fibers are usually added to increase its strength. In this study, the tribological behavior of glass fiber reinforced-polyamide 66 composite in contact with carbon steel under high contact pressure, sliding, and grease lubricated conditions is studied. Measurement of mechanical properties and SEM observations of composite sliding surfaces after different sliding cycle numbers indicate that sliding induces characteristic damage of the surface (peeled off fibers and scratching of polyamide) and a degradation in mechanical properties. These lead to an increase in friction and creep of the composite. The wear effect increases with the increase in sliding cycles, and the initial orientation of the fibers in the composite sliding surface has significant effects on the wear of the steel counterpart. The contribution of each phenomenon to the tribological behavior is discussed. The damage to the composite surface and the increase in contact temperature due to sliding have great effects on the tribological properties compared to the presence of wear debris in grease and wear on the steel. The effects of the hardness of the steel on the tribological properties are investigated, and it is found that wear of the composite is reduced by using softer steels.

Materials & Design, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Polyamide 66 is widely used in polymer sliding parts including polymer gear. These parts are used... more Polyamide 66 is widely used in polymer sliding parts including polymer gear. These parts are used under lubrication of oil and grease. In this study, the friction mechanism of the contact between polyamide 66 and a steel counterpart lubricated with additive-free polyalphaolefin8 oil was discussed by focusing on various parameters including the sliding surface roughness, normal load (contact pressure), sliding speed, temperature, and hardness of the steel counterpart. To explain the friction coefficient obtained under different test conditions, the theoretical minimum oil film thickness was calculated using the equation of the soft elastic hydrodynamic lubrication regime presented by Hamrock and Dowson considering the temperature dependence of oil viscosity and polymer mechanical properties, and the master curve of the relationship between Λ and the friction coefficient was proposed considering the change in the roughness on the sliding surface. In addition, the contributions of the ...