Tribology Online
Online ISSN : 1881-2198
ISSN-L : 1881-218X
Volume 11 , Issue 5
ITC Tokyo 2015 Special Issue (Part 2)
Showing 1-13 articles out of 13 articles from the selected issue
Short Communication
  • Florian Pape, Hans-Heinrich Gatzen, Gerhard Poll
    2016 Volume 11 Issue 5 Pages 547-550
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    A detailed knowledge of the interface between a sliding ball and an axial bearing surface allows to shed light on how to reduce friction and wear in bearings under slippage conditions. To study the interface, the contact was investigated applying micro-pin-on-disk tests without grease or oil lubrication. As pins sapphire half-balls and 100Cr6 steel bearing balls were used. As counterpart unused 100Cr6 steel (German standard corresponding to AISI52100) axial bearing surfaces were applied. It could be shown, that with the formation of surface layers, the frictional force was reduced. This effect is lower in case of a chemical inert sphere as contact partner. The transition from friction to stiction for varied Hertzian stress was observed. The spheres on the micro-pin-on-disk tester measured the frictional properties of the surface without ploughing effects. The micro-pin-on-disk tests allow to have a closer look on the start behavior of a metallic and sapphire test specimen on an axial bearing washer under ambient conditions.
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  • Vibhu Sharma, Sujay Bagi, Mihir Patel, Olusanmi Aderniran, Pranesh B. ...
    2016 Volume 11 Issue 5 Pages 551-555
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    Environmental regulations to reduce the emissions using exhaust gas recirculation (EGR) have resulted in higher soot level in the crankcase oil of diesel engines. Longer drain intervals have resulted in engines running 80000 kilometers or more before an oil change. This results in longer residence times of EGR soot in the crankcase and other parts of the engine drivetrain. The primary structure of soot from in-cylinder combustion is turbostratic carbon, as soot spends more time in the combustion chamber and in the crankcase it incorporates some of the chemistry of the aged oil as well as debris from the wear processes making the soot more abrasive. This study focuses on the use of multiple tools to examine the nature of soot from different engines of the same type but different age all using the same engine oil and similar duty cycles. This soot is compared with soot derived from a typical EGR diesel engine driven for a period of 80000 kilometers.
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  • Rakesh Somashekaraiah, Suvin P S, Divya Prakash Gnanadhas, Satish Vas ...
    2016 Volume 11 Issue 5 Pages 556-567
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    Mineral oils, chemically synthesized emulsifiers, and additives are the basic ingredients of commercially available metal working fluids. Its application in metal cutting have earned widespread acceptance all over the world. However, their harmful effects on the environment and life threatening health hazards to workers are of great concern and calls for a better alternative. In this present study a green metalworking fluid / green cutting fluid (GCF) was formulated and the performance was evaluated comparing with the commercial metal working fluid (COM) used in industries for machining processes. The obtained eco-friendly formulation has material properties equivalent to the commercial formulation without any environmental hazard. GCF is comparable to COM in corrosion prevention, inhibition of microbial growth and other machining processes. It was reported that vegetable oil based green cutting fluids have more of Gram-negative bacterial growth where as mineral oil based ones have more of Gram-positive bacteria. These bacteria cause environmental hazards and antimicrobials can be included for better antimicrobial properties. GCF supersedes COM by being non-toxic at LC50 >1000 mg/L and COM being toxic at LC50 < 100 mg/L according to OECD 203 tests methods. GCF, produced only from renewable sources is non-toxic and biodegradable and helps contribute towards green and sustainable manufacturing processes without any environmental pollution or hazards.
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Article
  • Jun Tomioka, Mikiko Oyabu, Norifumi Miyanaga
    2016 Volume 11 Issue 5 Pages 568-574
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    The purpose of this study is to find out the effects of hematocrit of the sealed blood on the leakage characteristics of blood cell components and plasma components in a mechanical seal, which separates blood from cooling water. The hematocrit was controlled to 0, 10, 20, 30 and 40%. Each component leakage was obtained by measuring the increase in the potassium ion concentration and the sodium ion concentration in the cooling water. It was revealed that each component leakage became larger with the increase of the hematocrit in the three-hour measurement. When changing the hematocrit from 20% to 30%, the volume percentage of the blood cell component leakage remarkably increased by 7.7 times. The friction characteristics of the mechanical seal under blood sealing and the hemolytic properties of the sealed blood were also studied. There is a typical trend under the mixed lubrication condition where the friction torque decreased with each of the sealed blood as the rotational speed increased. The hemolytic index of the sealed blood after the measurement experiments of the blood leakage increased with the increase of the hematocrit.
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  • Andreas Rosenkranz, Carsten Gachot, Esteban Ramos-Moore, Frank Mü ...
    2016 Volume 11 Issue 5 Pages 575-582
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    For many years already, a lot of research groups try to shed light on the origin of friction and to enhance the tribological performance of rubbing surfaces. In this context, the ability to tailor the tribological properties on different scales is of utmost importance. In this work, laser interference patterning is used to produce well-defined surface topographies with line- and cross-like patterns in order to modify the tribological performance under dry and lubricated conditions. Under dry conditions, the frictional behavior of line-like patterned surfaces having a periodicity of 9 μm are investigated using a ball-on-disk tribometer in linear reciprocating sliding mode as a function of the normal load and the relative alignment. Regarding mixed lubrication, the oil film lifetime of cross-like patterns (periodicity of 9 μm) is evaluated using a ball-on-disk tribometer (normal load of 5 N and sliding velocity of 5 cm/s) in rotational sliding mode. The experiments under dry friction demonstrate a significant friction reduction for the line-like surface patterned surfaces, independent on the respective alignment. Dependent on the used normal load, differences in the frictional behavior are observed. For the cross-like patterns under mixed lubrication, an increase of the oil film lifetime by a factor of 56 is achieved.
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  • Mamoru Oike, Masataka Kikuchi, Satoshi Takada, Takayuki Sudo, Tomoyuki ...
    2016 Volume 11 Issue 5 Pages 583-593
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    In the present study, a flow visualization experiment in the clearance between a clear floating-ring and a rotating journal was carried out in order to clarify the effect of the sweepback angle (θs) of the leading edge of the recess on the flow characteristics. Four types of the floating-rings with different recess geometries, i. e., the Young Leaf Mark, the square and the non-recessed geometries, were operated at a rotational speed of up to 45,000 rpm using liquid nitrogen as the working fluid to observe the interaction between source flow from the recess and rotating flow induced by the journal rotation in the clearance. The cavitation cloud inside the clearance was induced by viscous frictional heating and the pressure drop. The influence of the θs value on the flow characteristics was investigated by comparing flow coefficient (Cf) and the cavitation cloud area ratio (Ac) obtained from the visual image. Based on the experimental results, the dependence of the flow characteristics on the rotational speed was confirmed to be affected by the sweepback angle of the leading edge of the recess.
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  • Eugene Scanlon, Shaun R. Seibel, Thomas E. Hayden, Robert J. Bacchi, J ...
    2016 Volume 11 Issue 5 Pages 594-600
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    Fuel economy is overall a very high priority worldwide, but the value of fuel economy can vary to different stakeholders. Many governments set minimum fuel economy standards that force OEMs to make significant investment to achieve. Engine oils and friction modifiers can provide a small but cost-effective contribution to overall fuel economy in cars and trucks. Bench tests that evaluate frictional characteristics often do not correlate well to actual fuel economy benefit. Optimizing a friction modifier to maximize the benefit requires testing the same way that OEMs are required to test fuel economy. Using vehicles on chassis dynamometers, the Highway Test Procedure (HwFET) of the FTP 75 requirement which OEMs follow to quantify their Corporate Average Fuel Economy (CAFE) requirements in North America was modified and used to evaluate individual friction modifier (FM) components and their effects on fuel economy. Since OEM value propositions involve entire fleets, the effect of friction modifiers on fuel economy was tested using several types of vehicles. A new FM additive is shown to demonstrate more than twice the fuel economy benefit compared to glycerol monooleate (GMO), a standard FM used in many engine oils, even at half the treat rate. A Chevrolet 5.7 liter engine on a test stand was also adapted to screen individual components in engine oil and their effects on fuel economy. Results are shown for various components, including an apparent increase in fuel consumption due to the antiwear (AW) component ZDDP.
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  • Toshiaki Nishi, Kenta Moriyasu, Kenichi Harano, Tsuyoshi Nishiwaki
    2016 Volume 11 Issue 5 Pages 601-607
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    In the material designing process of footwear outer-soles, a grip property of rubber is of crucial importance under water or oil lubricated condition. In general, contact states between rubber and floors under lubricated conditions are influenced by various factors, i. e. viscosity of a lubricant, sliding velocity, normal force, surface roughness and wettability between the two substrates. It has been said that lubrication conditions can be distinguished based on Stribeck curves, which are described by the relationship between Sommerfeld numbers and dynamic friction coefficients. Wettability under the static condition is estimated by the spreading coefficient, which is used to evaluate the energy balance of interface free energies at a triple line. The purpose of this study is to investigate influences of surface free energies, viscosities, sliding velocities and surface roughnesses on dynamic friction coefficients of rubber under lubricated conditions. The influences of spreading coefficients on the behaviors of Stribeck curves and the relationship between dewetting velocities and dynamic friction coefficients are also discussed.
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  • Hitoshi Shindo, Tatsuya Sasaki, Kaoru Hashimoto, Masaki Moriya, Clara ...
    2016 Volume 11 Issue 5 Pages 608-613
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    To study relationship between friction and plastic deformation modes of single crystals, wear patterns were analyzed for BaSO4, an orthorhombic crystal having various cleavage faces and slip systems. Upon scanning a sapphire stylus along the b-axis at (0 0 1) face, formation of triangular deformation patterns extending outside the wear track were observed with optical microscopy. Atomic force microscopic analysis revealed that the triangular areas were elevated, and the two sides were formed by {2 1 0} cleavage steps, starting within the track, and continued by {1 1 0} slip steps outside the track. Upon scanning with heavier normal loads, lots of {0 1 1} slip steps were formed inside the triangles, presumably due to horizontal compression given by the stylus to the triangular areas isolated from the rest of the surface. Mechanism of the wear pattern formation was proposed. When the stylus was scanned along the a-axis, the wear tracks were segmented into short strips by {1 0 1} slips. Under heavier normal loads, the segment structures were partly destroyed by the stylus, presumably by (0 0 1) slip and cleavage, producing debris on both sides of the track. The changes in deformation patterns under heavier normal loads caused steeper increase in friction curves measured in the two directions. Different deformation modes were activated depending upon the scan directions, normal loads and locations relative to the stylus.
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  • Florian Beyer, Kai Willner
    2016 Volume 11 Issue 5 Pages 614-622
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    Friction has a significant effect on metal forming both in economic and technical terms. This is especially true for sheet-bulk metal forming, which is a combination of bulk metal forming and sheet metal forming. Contact loads of sheet forming processes are typically low to moderate. In contrast, very high contact loads occur in bulk metal forming. Therefore, a friction law, which is applicable for a broad range of contact loads, is necessary, if such a process has to be modelled accurately with the finite element method. A friction law fulfilling this demand is identified with the use of an elastic-plastic half-space model. The half-space model is used to determine the normal contact of rough surfaces and it is validated with experiments. In order to highlight the impact of the identified friction law, a typical sheet-bulk metal forming process is taken into account in the framework of the finite element method.
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  • Tomoharu Akagaki, Kazuma Kataoka, Masahiko Kawabata
    2016 Volume 11 Issue 5 Pages 623-631
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    Seizure behaviors of PEEK materials are studied using blocks on a ring wear tester under oil-lubricated conditions. The seizure processes are monitored with a particle counter to measure the number of wear particles in oil. Three kinds of block materials are tested: PEEK, PEEK composite filled with 30 mass% of carbon fiber, and white metal (WJ2). The ring is made of forged steel (SF540A). The sliding velocity is 15 and 19 m/s. The load varies between 294 and 1177 N. The ring temperature is measured with an alumel-chromel thermo-couple with a diameter of 0.5 mm, located 1mm below the frictional surface. Results indicate that the particle counter method can detect the seizure in the PEEK materials as well as in WJ2. However, the number of wear particle generated in the seizure of the PEEK materials is much less than in WJ2. It also increases in a mixed lubrication in WJ2. In contrast, wear particle is not detected appreciably in a mixed lubrication in the PEEK materials. Wear particles and wear scars on these materials are observed using a scanning electron microscope (SEM). The wear mechanisms in the seizure are discussed.
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  • Chisaki Hashimoto, Hikaru Okubo, Chiharu Tadokoro, Shinya Sasaki
    2016 Volume 11 Issue 5 Pages 632-638
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    Correlation between nano-mechanical and macro-tribological properties of the tribofilm derived from phosphoric additives was investigated. Macro friction test was performed at steel/steel contact under lubrication with poly-alpha olefin (PAO) containing these types of phosphoric additives; tricresyl phosphate (TCP), diphenyl phosphate (DPP), triphenyl phosphate (TPP). The nano-mechanical properties (viscoelasticity, adhesion, hardness, friction coefficient, and effective elastic modulus) of the tribofilms were evaluated by using atomic force microscopy (AFM) and nanoindentation tester. From the results of friction tests and surface analysis, the macro-tribological properties depended on the nano-mechanical properties of tribofilms derived from phosphoric additives under the boundary lubrication. In particular, the thick viscous tribofilm derived from the phosphoric additive exhibited the low friction phenomena. It was suggested that the nano-mechanical properties of tribofilms were the important factors governing the macro-tribological properties under the boundary lubrication.
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  • Kazuya Watanabe, Keiji Tanaka
    2016 Volume 11 Issue 5 Pages 639-645
    Published: September 15, 2016
    Released: September 15, 2016
    JOURNALS FREE ACCESS
    We newly developed the prototype calcium complex grease (Cx-S) which delivered a better temperature performance than traditional calcium complex greases and could keep its structure even over 200°C. This was achieved by combining the common calcium complex thickener technology with a new concept. In this report, the bearing life of several grease types was evaluated by ASTM D 1741. It was demonstrated that the bearing life of Cx-S wasn’t as long as urea grease, although it had excellent anti-oxidation performance. Additionally, leakage rate was calculated by the amounts of leaked grease from bearings during the test. Therefore, it was suggested that a physical factor such as shear stability of the grease is likely to cause shorter bearing life. Then, by using behenic acid instead of stearic acid - to improve shear stability of Cx-S - it was found that behenic type calcium complex grease (Cx-B) forms much thicker and stronger fiber micelles than stearic type (Cx-S). As a result, the shear stability of Cx-B was strongly improved and bearing life was extended by 50% compared to Cx-S.
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