Faculty Profiles - UMEHARA, Noritsugu

Evaluation of Mechanical Characteristics of Tribofilm Formed on the Surface of Metal Material Due to Friction under Lubrication with Automatic Transmission Fluid Reviewed International journal

Tokoroyama Takayuki, Nishimoto Takashi, Murakami Yasuhiro, Honda Akiyuki, Mitsui Hideaki, Terai Yusuke, Murashima Motoyuki, Lee Woo-Young, Umehara Noritsugu

Tribology Online Vol. 16 ( 4 ) page： 255 - 262 2021

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

In this study, nano-scratch tests were conducted using atomic force microscope (AFM) to clarify the hardness of a tribofilm derived from an additive (Fluid A or Fluid B in automatic-transmission fluid) formed on an SKS3 cold work tool steel substrate surface. Comparisons between nano-indentation hardness tests and AFM nano-scratch tests were performed for each specimen. Prior to these tests, the tribofilms on the SKS3 substrate were examined with energy-dispersive spectroscopy (EDS). In order to calculate the hardness of the tribofilm from the nano-scratch results, we assumed that the AFM diamond tip acted as an abrasive to plough the tribofilm. The phosphorous-derived tribofilm formed from Fluid A was harder than the sulfur-derived tribofilm from Fluid B, and it was calculated that the phosphorous-derived tribofilm was approximately 2.64 GPa and the sulfur-derived tribofilm was 1.89 GPa. After 10 nano-indentation hardness tests on each tribofilm, the maximum indentation depth into the tribofilm formed from Fluid A was approximately 31 nm, while it was approximately 36 nm for Fluid B. These results are qualitatively consistent with the hardness results obtained by the AFM nano-scratch test method.

DOI： 10.2474/trol.16.255

The Tribological Properties of Hydrogenated DLC Coating Lubrication with Additive Having Glycerol and Phosphonate Structure Reviewed International coauthorship International journal

Kani Takumi, Tokoroyama Takayuki, Umehara Noritsugu, Murashima Motoyuki, Lee Woo-Young, Yagishita Kazuhiro

Tribology Online Vol. 16 ( 4 ) page： 263 - 270 2021

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

In general, several mechanical parts are subjected to friction and wear. To prevent wear and high friction coefficient under lubrication, additives can work to reduce friction force, to build up thin film on surfaces which is so-called tribofilm. Recently, Diamond-Like Carbon (DLC) is focused because it has excellent low friction and high wear proof as solid lubricant. However, several researchers already reported that tetrahedral amorphous carbon (ta-C) showed abnormal wear when it rubbed with glycerol mono-oleate (GMO) that is a kind of additive, although it showed very low friction coefficient. To improve tribological properties, new additives were developed that had both phosphate-oxide structure derived from ZnDTP which had high wear resistance and hydroxy group derived from GMO in one structure. To clarify the effects of the additives, friction tests were performed fixed-roller-on-disk type rotating friction tester. In the friction tests, hydrogenated amorphous carbon (a-C:H) disks, and a-C:H coated rollers were used under boundary lubrication condition at 20-80°C. Friction tests were conducted in Poly-α-olefin (PAO) oil with each GMO and the additives. The results exhibited that a-C:H gave ultra-low friction with the additive. Elemental analysis of the surface showed that tribofilm of phosphorus and oxygen was detected on the a-C:H surface in the additive used condition.

DOI： 10.2474/trol.16.263

The Clarification of Friction Mechanism for Carbonaceous Hard Coatings by in-situ Observation of Friction Area with Reflectance Spectroscopy Invited

New study on tribological performance of AA7075-TiB2 nanocomposites Reviewed International coauthorship

Pan Shuaihang, Saso Tomohiro, Yu Ning, Sokoluk Maximilian, Yao Gongcheng, Umehara Noritsugu, Li Xiaochun

TRIBOLOGY INTERNATIONAL Vol. 152 2020.12

The Clarification of Friction Mechanism in Oil Lubrication for CNx Coating by In-Situ Observation of Friction Area with Reflectance Spectroscopy Invited

UMEHARA Noritsugu

JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS Vol. 65 ( 11 ) page： 684 - 687 2020.11

ポリ塩化ビニル溶媒への交流電場援用マイクロプラスチック突起の創製 Reviewed

山田雄聖，野老山貴行，村島基之，梅原徳次

日本機械学会論文集 Vol. 86 ( 892 ) page： 20-00228 2020.11

Re-Organization of Technical Support Staffs in Nagoya University Invited

UMEHARA Noritsugu, KOGA Kazushi, FUJIWARA Fumiharu, SAWAKI Koji, YAMAMOTO Kouji, TACHIBANA Kazushi, MIZUGUCHI Ikuyo

Journal of the Japan Society for Precision Engineering Vol. 86 ( 9 ) page： 662 - 665 2020.9

UMEHARA Noritsugu

Journal of The Surface Finishing Society of Japan Vol. 71 ( 9 ) page： 547 - 550 2020.9

コーティング電気メス先端の炭化物付着抑制手法の開発 Reviewed

野老山貴行，小林将大，村島基之，梅原徳次，小川航生，萬隆行，内田淳一

日本機械学会論文集 Vol. 86 page： 20-00273 2020.9

Enhancement of speed of surface roughness improvement by using a two mixed abrasive slurry method to polish glass surfaces Reviewed

TAKENO Hiroaki, TOKOROYAMA Takayuki, MURASHIMA Motoyuki, UMEHARA Noritsugu, CHIBA Shogo

Journal of the Japan Society for Abrasive Technology Vol. 64 ( 8 ) page： 428 - 435 2020.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society for Abrasive Technology

This study was performed to find a method to reduce the consumption of expensive diamond abrasive grains in polishing glass substrates, and to mix low-hardness abrasives with diamond abrasives to reduce costs and achieve early improvement of surface roughness. The effects of the size of the GC abrasives (approximately 127 μm, 75 μm, and 13 μm), abrasive concentration, and types of abrasives (WA and B4C) were clarified for low-hardness abrasives. The abrasive grains were fluorescently stained with rhodamine B to determine their behavior on the polished surface in-situ. The results indicated improved surface roughness by using two types of mixed abrasive grains. In addition, the large-grain GC abrasives moved or were shown to be trapped in the gaps of the fibers of the natural silk polishing pad used for polishing. On the other hand, diamond grains with an average grain size of 1.0 μm moved between the natural silk polishing pad and the glass substrate regardless of the fiber orientation.

DOI： 10.11420/jsat.64.428

CiNii Books

金ナノ粒子法を用いた表面増強ラマン分析による炭素系薄膜の極表面分析 Reviewed

野老山貴行，梅原徳次，村島基之

トライボロジスト Vol. 65 ( 8 ) page： 517 - 525 2020.8

New study on tribological performance of AA7075-TiB2 nanocomposites Reviewed International coauthorship International journal

Shualihang Pan, Tomohiro Saso, Ning Yu, Maximillan Sokoluk, Gongcheng Yao, Noritsugu Umehara, Xiaochun Li

Tribology International Vol. 152 page： 106565 2020.8

The wear classification of MoDTC-derived particles on silicon and hydrogenated diamond-like carbon at room temperature Reviewed International journal

K. A.M. Kassim, T. Tokoroyama, M. Murashima, N. Umehara

Tribology International Vol. 147 page： 106176 2020.7

Language：English Publishing type：Research paper (scientific journal)

Molybdenum dithiocarbamate (MoDTC) is well-known as a friction-modifier in engine oil but has wear accelerating effects on DLC/steel sliding contact. Since MoDTC was reported degradable to other materials, the effect of each material on wear acceleration has not been clarified yet. Therefore, it is necessary to divide which Mo-derived compound has a major role to enhance wear. Thus, powder-type MoDTC, MoO3, Mo2C, MoS2, and Mo were dispersed into Poly-alpha-olefin (PAO), and tested on a-C:H and Si-DLC against steel ball at room temperature. For Mo2C, MoDTC, and MoO3, the specific wear rate of a-C:H was approximately 3.4 × 10−5, 3.2 × 10−6 and 1.5 × 10−6 mm3/Nm, respectively. MoDTC indicated higher affection than MoO3 regardless of the particles’ hardness. Si-DLC showed better wear prevention compared to a-C:H.

DOI： 10.1016/j.triboint.2020.106176

Effect of mesh structure of tetrahedral amorphous carbon (ta-C) coating on friction and wear properties under base-oil lubrication condition Reviewed International coauthorship International journal

Mohd Muhyiddin Bin Mustafa, Noritsugu Umehara, Takayuki Tokoroyama, Motoyuki Murashima, Akinori Shibata, Yoshiharu Utsumi, Hideki Moriguchi

TRIBOLOGY INTERNATIONAL Vol. 147 page： 105557 2020.7

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

This study examined the tribological properties of novel mesh tetrahedral amorphous carbon (Mesh ta-C). Subsequently, comparison was made with conventional ta-C and a-C:H coatings under base-oil lubrication via cylindrical-pin-on-disk tribo-tester. Analysis of wear track was conducted using field-emission-scanning-electron-microscope (FE-SEM), atomic-force-microscopy (AFM), and Raman-spectroscopy. The friction coefficient for Mesh ta-C and conventional ta-C revealed a similar pattern with regard to loads. The Mesh ta-C had excellent wear resistance, where the wear rates at loads of 20 N was five and 20 times lower than conventional a-C:H and ta-C, respectively. High wear resistance of Mesh ta-C characterized by inhibition of brittle micro-fracture propagation, less in abrasive particle created during friction test, and suppressing the effect of graphitization-induced wear on the contact surface.

DOI： 10.1016/j.triboint.2019.01.016

Effect of defects on wear behavior in ta-C coating prepared by filtered cathodic vacuum arc deposition Reviewed International coauthorship International journal

Woo-Young Lee, Young-Jun Jang, Takayuki Tokoroyama, Motoyuki Murashima, Noritsugu Umehara

DIAMOND AND RELATED MATERIALS Vol. 105 page： 107789 - 107789 2020.5

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

This study examined the tribological behavior of a ta-C coating fabricated at a substrate bias of -100 V via filtered cathodic vacuum arc (FCVA) deposition. Defects in the ta-C coating were categorized as droplets, pores, and spikes, considering the morphological, structural, and mechanical properties of the ta-C surface. A friction test was conducted at 170 degrees C in ambient air using a ball-on-disk tribometer. The friction coefficient was 0.08 during the steady state and the wear rate was 4.3 x 10(-6) mm(3)/Nm. To explain the friction and wear behavior, the morphological and structural properties of the defects in the designated area were compared among different sliding cycles.

DOI： 10.1016/j.diamond.2020.107789

The Surface Enhanced Raman Scattering Analysis for Carbonaceous Coating by Using Au Nano-Particles Reviewed International journal

T. Takayuki, M. Murashima, N. Umehara

TRIBOLOGY ONLINE Vol. 15 ( 5 ) page： 300 - 308 2020.5

Tribology in Shaver

TOKOROYAMA Takayuki, UMEHARA Noritsugu

JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS Vol. 65 ( 4 ) page： 236 - 241 2020.4

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

From time immemorial, shaving one’s beard has been continued. Using razor or electric shaver is common for all male adult to show their cleanliness recently. The custom for shaving my beard by myself was harbingered by World War I and II. Tremendous safety razors were provided by US government to frontline infantry, then they acquired a custom of “shaving by myself”. An electric shaver was invented early of the 20th century, and it is divided two shaving motion, a rotation or a reciprocation. In this article, investigating the relation between inner blade’s edge radiuses and pulling force, clarifying differences of shaving mechanism of a rotation or a reciprocation type shaver by a high speed camera with measuring pulling force simultaneously are explained.

DOI： 10.18914/tribologist.65.04_236

New Droplet Removal Polishing Method for Diamond-Like Carbon with Carbon Fiber Brush Reviewed International journal

Murashima Motoyuki, Imaizumi Yusuke, Umehara Noritsugu, Tokoroyama Takayuki

International Journal of Automation Technology Vol. 14 ( 2 ) page： 190 - 199 2020.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Fuji Technology Press Ltd.

In this paper, we propose a new polishing method for diamond-like carbon (DLC) coatings using a carbon fiber brush (CFB). Surface finishing is an important process for DLC coating applications. A lapping process is widely used for attaining tetrahedral amorphous carbon (ta-C) coatings, which are a type of DLC coating containing many droplets, to obtain fine flat surfaces. The lapping process removes protuberant parts of droplets rather than the entire droplet. In this paper, we propose a new polish brush material made of carbon fiber, called CFB. Carbon fiber has both mechanical strength due to its hard carbonaceous material and flexibility due to its fiber structure. In polishing tests, CFB removed droplets from ta-C coatings and the removal effect increased with the shortening of the brush length. The surface profiles of the polished surfaces indicated that a shorter brush length yielded deep scratch marks on ta-C surfaces. Consequently, the arithmetic average surface roughness of the polished ta-C surfaces, Sa, had almost the same value as that of a non-polished surface. Here, we show the ability of CFB to remove the droplets without an increase in the surface roughness. The CFB with the longest brush length in the present study (12 mm) showed a ten-point average roughness SZJIS= 75 nm and Sa= 4.7 nm, which were 59% and 22% lower than those of the non-polished surface, respectively. Furthermore, the longest CFB removed the entire droplets whereas a shorter CFB merely removed the protuberant part of the droplets. The result indicates that CFB polishing can remove entire droplets, which result in abrasive wear or deterioration. From other polishing tests, the optimum polishing distance was determined. Shorter polishing distances could not remove droplets sufficiently whereas longer polishing distances caused deep scratches on ta-C surfaces due to the material transferred to the CFB. Accordingly, the polishing distance of 600 m showed the best surface finishing with SZJIN= 25 nm and Ra= 0.43 nm, which were 86% lower than and similar to those of the non-polished ta-C surface, respectively.

DOI： 10.20965/ijat.2020.p0190