Faculty Profiles - UMEHARA, Noritsugu

Tribological properties of ta-CNx coatings with different nitrogen content under oil lubrication conditions Reviewed

Effect of Electric Field on Adhesion of Thermoplastic Resin against Steel Plate, Reviewed

M. Murashima, N. Umehara, H. Kousaka, X. Deng

Tribology Online Vol. 12 ( 2 ) page： 42-48 2017.2

Microscopic origin of ultra-low friction coefficient between the wear track formed on carbon nitride coating and transfer layer on sliding ball in friction tests under dry N2. Reviewed International journal

H. Inoue, S. Muto, S. Arai, H. Wasada, N. Umehara

Surface Coatings & Technology Vol. 313 page： 31-39 2017.2

Effects of Ceramic Counterpart Material on Wear Property of a-C:H Coating under Reviewed

T. Yamanouchi, X. Deng, Y. Tanaka, N. Umehara, H. Kousaka

Tribologist Vol. 62 ( 1 ) page： 52-58 2017.1

Clarification of effect of transformed layer and oil film on low friction coefficient of CNx coating in PAO oil lubrication by in-situ observation of friction area with reflectance spectroscopy Reviewed

H. Nishimura, N. Umehara, H. Kousaka, M. Murashima

Tribology International Vol. 113 page： 383-388 2017.1

Depth Profile of Oxygen of Diamond-Like Carbon Sliding Under Pressurized Hot Water Reviewed

M. R. B. Mohamad Zin, K. Okuno, N. Umehara, N. Inayoshi, K. Sasaki, S. Kawara,H. Kousaka

Tribology Online Vol. 12 ( 1 ) page： 8-17 2017.1

Deng Xingrui, Hattori Takafumi, Umehara Noritsugu, Kousaka Hiroyuki, Manabe Kazuyoshi, Hayashi Keiji

THIN SOLID FILMS Vol. 621 page： 12 - 18 2017.1

Language：English Publisher：Thin Solid Films

Carbon nitride (CNx) coatings exhibit a wide range of attractive properties that make them suitable for demanding mechanical and tribological applications. In this study, an ion beam assisted filtered arc deposition (IBA-FAD) method has been developed for the deposition of tetrahedral amorphous carbon nitride (ta-CNx) coatings. The ta-CNx coatings with various nitrogen contents were deposited by controlling the nitrogen flow to investigate the effects of nitrogen content on their tribological behavior. The composition and structure of the ta-CNx coatings were evaluated using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The tribological properties were examined using a ball-on-disk tribo-tester under oil lubrication condition. The results showed that nitrogen contents of ta-CNx coatings were restricted to the range of 0–11 at.% by nitrogen ion density. The hardness decreased with an increase in the nitrogen content as nitrogen decreased the fraction of sp3 carbon in the coatings. The ta-CNx coatings exhibit low friction under oil lubrication and the maximum value was obtained for samples containing 8 at.% of nitrogen. ta-CNx with 8–11 at.% of nitrogen exhibited markedly low wear rate.

DOI： 10.1016/j.tsf.2016.11.025

Clarification of high wear resistance mechanism of ta-CNx coating under poly alpha-olefin (PAO) lubrication Reviewed

Tribological properties of ta-CNx coatings with different nitrogen content under oil lubrication conditions Reviewed International journal

X. Deng, T. Hattori, N. Umehara, H. Kousaka, K. Manabe, K. Hayashi

Thin Solid Films Vol. 616 page： 134-140 2017.1

Xiaoxu Liu, Ryo Yamaguchi, Noritsugu Umehara, Xingrui Deng, Hiroyuki Kousaka, Motoyuki Murashima

TRIBOLOGY INTERNATIONAL Vol. 105 page： 193 - 200 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Tetrahedral amorphous carbon nitride (ta-CNx) is suitable for tribological application due to its excellent mechanical and adhesion properties. In this study, ta-CNx coatings with N/C ratios (0-11%) are deposited by ion beam assisted filtered arc deposition (IBA-FAD), and the tribological properties are investigated with a ball on-disk tribo-tester. The results show that nitrogen doping decreases the fraction of sp(3) bonding, hardness, Young's modulus and roughness. In oil ta-CNx presents slightly decreasing friction coefficient and improving wear resistance with the N/C ratio, indicating softer ta-CNx with better wear resistance. The lower surface roughness after friction of high nitrogen content ta-CNx makes it more likely to transit to mixed lubrication, resulting in lower contact load that can explain the better wear resistance.

DOI： 10.1016/j.triboint.2016.10.016

Fabrication of Thin Solid Coating and Tribology with Plasma and Ion Beam Process

Future of Tribology and Technology Education with Tribology

UMEHARA Noritsugu

JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS Vol. 62 ( 10 ) page： 609 - 609 2017

KOUSAKA Hiroyuki, UMEHARA Noritsugu

Journal of the Japan Society for Precision Engineering Vol. 83 ( 4 ) page： 319 - 324 2017

Effect of drill surface texturing on back burr height with solid lubricating sheet in titanium alloy drilling Reviewed

OYAMA Shintaro, UMEHARA Noritsugu, KOUSAKA Hiroyuki, DENG Xingrui, MURASHIMA Motoyuki, HORIE Shigeru, MATSUYAMA Yousuke

Transactions of the JSME (in Japanese) Vol. 83 ( 849 ) page： 16-00378 - 16-00378 2017

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

This paper describes about the effect of drill surface texturing on height of back burr in titanium alloy drilling process with solid lubricating sheet. Titanium alloy is difficult to conduct drilling because titanium alloy is hard and ductile material. And the workers cannot use plenty of liquid coolant for preventing the productivity decline when the work places are above their heads in production fields. Therefore drills are exchanged frequently even though the cost increases. In this study, we measured the cutting force by a loadcell to know the effect of drill surface texturing and solid lubricating sheet on drilling process of work pieces made of Ti-6Al-4V. As the results, drill with rough textured rake surface showed high burr height in exit of Ti-6Al-4V. On the other hand, drill with rough textured flank surface showed low burr height only if drilling with solid lubricating sheet. Moreover, drill with the specific texturing on flank surface by wire electric discharge machining showed low burr height.

DOI： 10.1299/transjsme.16-00378

Analysis of Wear Track on DLC Coatings after Sliding with MoDTC-Containing Lubricants Reviewed International journal

Ohara Kenji, Hanyuda Kiyoshi, Kawamura Yasushi, Omura Kentaro, Kameda Imari, Umehara Noritsugu, Kousaka Hiroyuki

TRIBOLOGY ONLINE Vol. 12 ( 3 ) page： 110-116 - 116 2017

Friction and Wear Properties of Tetrahedral Si-Containing Hydrogenated Diamond-Like Carbon Coating under Lubricated Condition with Engine-Oil Containing ZnDTP and MoDTC Reviewed International journal

Komori Kentaro, Umehara Noritsugu

Tribology Online Vol. 12 ( 3 ) page： 123 - 134 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Society of Tribologists

In this study, we investigated tribological properties of “tetrahedral” Si-containing hydrogenated DLC coating (TMS coating) during sliding against steel or cast-iron lubricated with engine-oil containing MoDTC and ZnDTP additives. TMS coatings derived from only tetramethylsilane were prepared using PACVD with high-bias process. TMS coating had the highly carbon sp3 bonded structure induced by Si (over 20 at.%) with high hydrogen content (30 at.%). TOF-SIMS analysis showed that TMS coating could form the additive-derived tribofilm on both of the non-ferrous coating surface and the ferrous counter surface to promote Mo-sulfide formation effectively, leading a low friction coefficient. The tribo-chemical reactions were related not only to Mo-sulfides formation, but also reduction of Mo-oxides. Mo-oxides could react with DLC material and induce hydrogen evolution and transformation into further weak carbon structure, causing an increasing wear of hydrogenated DLCs. TMS coating showed no significant wear in spite of plenty hydrogen content. Si induced sp3 bond and could act so as not to induce clustering of the sp2 phase. This could inhibit increasing wear of the DLC in the presence of MoDTC. The effectiveness of TMS coating in friction and wear behavior was shown to depend on tribo-chemical reactions and transformation of carbon bond structure.

DOI： 10.2474/trol.12.123

Proposal of lightweight and low starting torque slide bearing with looped carbon fibers brush Reviewed

SHITAKA Takuya, MURASHIMA Motoyuki, UMEHARA Noritsugu, TSUKIYAMA Yosuke, NITTA Isami, KOUSAKA Hiroyuki, DENG Xingrui

Transactions of the JSME (in Japanese) Vol. 83 ( 854 ) page： 17-00252 - 17-00252 2017

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

This paper addresses a novel lightweight and low starting torque bearing with looped carbon fiber brush (LCFB). LCFB simulates bristle of living being. Moreover, the static friction coefficient is nearly equal to the kinetic friction coefficient. By applying LCFB to a slide bearings, where a shaft is supported by multiple LCFBs, it is realized low starting torque bearings as well as lightness compared to conventional ball bearings. In this paper, we manufacture prototype LCFB slide bearings. With the bearings, we compare friction torque between LCFB slide bearings, slide bearings and deep groove ball bearings. As results, the ratio of starting torque to regular torque of LCFB slide bearing is from 0.93 to 1.07 which is smaller than that of the slide bearing. When micro-spline shaft is used as a mating material of LCFB slide bearing, the torque reduces because of decrease of real contact area between LCFB and mating materials. In addition, since LCFB utilize elastic deformation of fibers, LCFB slide bearings are not endurable in heavy radial load as high as load rating of ball bearing. Therefore, we define the load capacity of LCFB slide bearing from buckling load of a carbon fiber bundle to avoid overload state. We propose the load capacity as a design guideline of LCFB slide bearings.

DOI： 10.1299/transjsme.17-00252

Depth Profile of Oxygen of Diamond-Like Carbon Sliding under Pressurized Hot Water Reviewed International coauthorship International journal

Bin Mohamad Zin Mohd Rody, Okuno Kiichi, Sasaki Keiji, Inayoshi Naruhiko, Umehara Noritsugu, Kousaka Hiroyuki, Kawara Shingo

Tribology Online Vol. 12 ( 1 ) page： 8 - 17 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Society of Tribologists

The wear mechanism of diamond-like carbon (DLC) in hot, pressurized water has been studied by the oxygen depth profile of DLC films pre and post a sliding test. The sliding test between DLC films coated on chromium molybdenum steel (JIS SCM420) pins and austenitic stainless steel (JIS SUS316) plates was conducted in a water environment by using high temperatures of 100, 200, 250 and 300°C and a high-pressured (10 MPa) autoclave friction tester. The dissolved oxygen concentration (DO) was 0.52 mg/L for oxygen-poor water and 40 mg/L for oxygen-rich water. The experimental results showed that the specific wear rate of DLC was strongly related to the water temperature and the DO concentration. The specific wear rate in both cases of oxygen-poor and oxygen-rich water showed a temperature dependency. When the temperature was below 200°C, the specific wear rate of DLC did not depend on the DO concentration. On the other hand, when the water temperature was more than 200°C, the specific wear rate drastically increased with the DO concentration. In order to prove the effect of oxidation on the wear rate of DLC, the depth profile of the oxygen concentration was compared to that of the carbon concentration on the inside and outside of the wear scar of DLC after sliding tests in hot, pressurized water. When the concentration of DO in the water was low at 0.52 mg/L, the O/C ratio was not affected by the water temperature. On the other hand, when the concentration of DO in water was high at 40 mg/L, the O/C ratio of the top surface increased from 0.05 to 0.18 with an increase in the water temperature on the inside of the wear scar of DLC, where the O/C ratio on the inside of the wear scar was higher than that on the outside of the scar. On the basis of the estimated rate of reaction between DLC and oxygen, determined from a linear relationship between ln (Oxidation wear volume) and the inverse temperature, it was concluded that the oxidation of DLC governed the wear of DLC in hot, pressurized water. Friction was found to enhance the oxidation wear of DLC from the estimated activation energy.

DOI： 10.2474/trol.12.8

Effect of Electric Field on Adhesion of Thermoplastic Resin against Steel Plate Reviewed International journal

Murashima Motoyuki, Umehara Noritsugu, Kousaka Hiroyuki, Deng Xingrui

Tribology Online Vol. 12 ( 2 ) page： 42 - 48 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Society of Tribologists

This work shows new method which controls adhesion strength between acrylic resin and metal mold with electric field. Usage of electric field is considered as a new solution to control adhesion of thermoplastic resin in Carbon-Fiber-Reinforced ThermoPlastic (thermoplastic CFRP) stamping process because this method can prevent CFRP from its degradation. In this work, we establish new adhesion tester which can apply Direct Current (DC) or Alternating Current (AC) field on metal specimens. In the results, when DC −12 V/mm is imposed on metal specimens, adhesion strength increases to 0.81 MPa which is 57% higher than that of no field condition. Negative component of surface energy after imposing DC −12 V/mm on metal specimens is 7.6 mJ/m2. This value is 56% smaller than that of no field condition. When AC electric fields is imposed, adhesion strength decreases from no electric field condition. The most effective AC field condition is AC 10 V/mm with 1 MHz, in which case adhesion strength is 0.29 MPa. This value is 44% lower than that of no field condition.

DOI： 10.2474/trol.12.42

Development of radio knife tip to prevent adhesion of coagulated blood by separate type thermosyphon Reviewed

TOKOROYAMA Takayuki, OSUKA Misato, UMEHARA Noritsugu

Transactions of the JSME (in Japanese) Vol. 83 ( 845 ) page： 16-00123 - 16-00123 2017

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

Radio knives are common tools in surgery. The adhesion of the tip of a radio knife to the human body through the coagulation of blood is a severe problem. A solution to this problem, suggested by other authors, is to cool the tip of the radio knife. However, introducing a cooling system, such as circulating water inside the tip with a pump, requires additional wires and pipes and may also distract the surgeons. To overcome these issues, we consider the possibility of embedding a separate type thermosyphon to cool the radio knife tip without any additional wires and pipes. The important parameters are the tip length, tip diameter, inner tip diameter, enclosure ratio of the working fluid, and grip length. First, to clarify the heat-transport possibilities, the top of the tip of a separate type thermosyphon radio knife was heated by a ceramic heater; this was done to measure the temperature difference between the radio knife tip surface and a heat release part. Second, suitable values for the tip length, diameter and other important parameters were considered. It was concluded that the highest cooling efficiency is obtained when the heating area is limited between 200 and 250 mm2 of the knife tip surface area. The inner pipe was indispensable to transport generated heat from the tip to the radio knife end. Consequently, it was revealed that the effective diameter of inner pipe was 0.48 mm in this research. To simulate the conventional surgery situations, the radio knife tip was immersed to blood and applied voltage to generate heat at the tip. It demonstrated 45.9 degree C at the maximum temperature while it was activated. Furthermore, the coagulation at the peripheral of the tip was observed, accordingly, the separate type thermosyphon radio knife exhibited a stop bleeding ability.

DOI： 10.1299/transjsme.16-00123

In-Situ Observation Apparatus for Structure Change of Topmost Layer of Cabonaceous Hard Coatings during Sliding with Refrectance Spectroscopty

NISHIMURA Hidenori, KOUSAKA Hiroyuki, UMEHARA Noritsugu

JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS Vol. 62 ( 7 ) page： 461 - 464 2017

Effects of ceramic counterpart material on wear property of a-C:H coating under various temperatures Reviewed

Yamanouchi T., Xingrui D., Tanaka Y., Umehara N., Kousaka H.

Toraibarojisuto/Journal of Japanese Society of Tribologists Vol. 62 ( 1 ) page： 52 - 58 2017

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Toraibarojisuto/Journal of Japanese Society of Tribologists

Carbon coatings have a keen attention according to its low friction, high hardness and high wear resistance properties. There are needs to apply carbon coatings into ceramic mechanical parts, such as mechanical seal. However the tribological properties of carbon coatings when slid against ceramics are still not investigated sufficiently. Generally tribological behaviors are affected by a counterpart material. Therefore more fundamental researches about counterpart material are necessary. In this research tribological behaviors of carbon coating when slid against various counterpart material, including SiC, SiC(O) that is SiC after annealing at 1000°C, Si3N4, Al2O3, Al2O3(Si) that includes more Si atomic concentration than Al2O3and Si wafer at various temperatures in air have been investigated. Carbon coating when slid against SiC showed the lowest wear rate at 23°C, and carbon coating when slid against Si3N4showed the lowest wear rate at 140°C and carbon coating when slid against SiC(O) showed the lowest friction coefficient at all temperature.