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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.

DOI： 10.3390/met9070783

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

Sintered materials are superior in productivity because of their simple process, but their mechanical properties are low. To improve the mechanical properties of sintered materials, we focus on liquid-phase sintering. In this study, we selected boron as sintering aids and evaluated on the effect of the addition quantity of boron (0-0.6 mass%) to the mechanical properties of liquid-phase sintered and heat-treated materials. In the test range of this study, the tensile strength of material with an additional quantity of boron of 0.1 mass% showed the highest value, 1386 MPa, which is about 35% higher compared to the tensile strength of material without adding boron. On the other hand, materials with an additional quantity of boron of 0.2 mass% or higher showed higher-density than material with an additional quantity of boron of 0.1 mass%, but both their elongation and tensile strength were significantly decreased. The precipitates changed between the boundary of the quantity of boron added of 0.1 and that of 0.2 mass%. Only Fe 23 B 6 was formed in the material with the boron addition amount of 0.1 mass% or less, and Fe23B6 and Fe2B were formed in the material with the boron addition amount of 0.2 mass% or more. By cross-sectional observation of the test specimen after the tensile test, it was confirmed that in the material with the boron addition amount of 0.2 mass% or more cracks occurred and propagated at the Fe23B6/Fe2B interface and finally resulted in fracture. In the material with the boron addition amount of 0.1 mass%, however, such a fracture was not confirmed. The phenomena could be explained the fact that the mechanical properties were sharply changed between the quantity of boron added of 0.1 mass% and 0.2 mass%. The existence of Fe23B6/Fe2B interface would significantly affect the strength of the liquid-phase sintered materials.

DOI： 10.1299/mej.19-00297

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Japan Society of Mechanical Engineers  

In this study, sintered and powder-forged rollers and gears with different densities and nickel contents were fatigue-Tested using a roller testing machine and a gear testing machine in order to elucidate their fatigue strength. The densities of the sintered and powder-forged rollers and gears were in the range 7.01 g/cm3 to 7.84 g/cm3, and the nickel contents of the metal powders were chosen as 0.5 % and 3.0 %. These experimental results were compared with the results for ingot steel ones. The hardness near the surface of the test specimens with a nickel content of 3.0 % was lower than that of the other ones. The pores in the sintered rollers became smaller or disappeared upon hot forging. The failure modes of the rollers and gears were mainly spalling due to subsurface cracking and pitting due to surface cracking, respectively. The fatigue strength of the sintered rollers and gears was the lowest in this experimental range. The fatigue strength of the powder-forged rollers and gears was roughly equivalent to that of the ingot steel ones, respectively. The fatigue strength of the test specimens increased as their density increased. It was clear that the fatigue strength of the sintered and powder-forged rollers and gears was proportional to the hardness at the failure depth for nickel contents of 0.5 % and 3.0 %. In other words, the fatigue strength of the rollers and gears with a nickel content of 3.0 % was similar to those of the others because of the toughness effect of nickel under the same material density.

DOI： 10.1299/jamdsm.2017jamdsm0073

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC MECHANICAL ENGINEERS  

In this paper, a mechanism of variation in axial bolt force in pipe flange connection during bolt tightening process is investigated. Especially, Correlation between torque coefficient and bolt preload is investigated. The actual pipe flange connection is tightened by a wrench due to the torque control method. Axial bolt forces were measured in the tightening process. The three types of gasket are chosen in this paper. As a result the good relationships are seen between torque coefficient and axial bolt force. The effect of gasket material on the relationships between torque coefficient and bolt preload is not seen.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Japan Society of Mechanical Engineers  

<p>In this study, sintered and powder-forged rollers and gears with different densities and nickel contents were fatigue-tested using a roller testing machine and a gear testing machine in order to elucidate their fatigue strength. These experimental results were compared with the results of ingot steel ones. The hardness near the surface of the test specimens with higher nickel content was smaller than that of the other ones. The pores in the sintered rollers became smaller or were disappeared by the hot forging. The fatigue strength of the sintered rollers and gears was the lowest in this experimental range. The fatigue strength of the powder-forged rollers and gears was roughly equivalent to that of the ingot steel ones. The fatigue strength of the test specimens increased as their density increased, and was hardly influenced by the nickel content in this experimental range. It was clear that the fatigue strength of the sintered and the powder-forged rollers and gears was proportional to the hardness at the failure depth for each nickel content.</p>

DOI： 10.1299/jsmeimpt.2017.05-03

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<p>Recently, the gear is required of high strength, reliability, and surface damage resistance under severe service condition to achieve the weight saving and downsizing of a product. It is necessary to understand the influence of the surface profile on the scuffing resistance. The shot peening is able to form the arbitrary surface profile with the changes of peening conditions to the metal surface. When the effective surface profile will be found to increase the lubrication property, the metal surface will be obtained with both the surface strength and the surface lubricity. In this paper, the influence of surface profile with the fine shot peening, which is able to form the arbitrary surface profile, on the scuffing resistance in the rolling-slipping contact machine element was investigated. The scuffing test using the two cylinder rolling contact test machine was carried out. The test rollers processed with shot peening were used in the scuffing test.</p>

DOI： 10.1299/jsmeimpt.2017.07-11

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC MECHANICAL ENGINEERS  

In this study, the creep deformation in the threaded joint are discussed using a finite element method, and evaluated the influence of the dimensions of bolt and clamped parts. The stress and creep strain distributions are calculated using the Finite Element Analysis. The occurrence and the propagation of the creep deformation and influence of the creep deformation on the axial bolt force were discussed. It was found that the creep deformation occurred at the bearing surfaces and the engagement screw thread mainly at the elevated temperature. The creep deformation was a cause of the reduction in axial bolt force.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Universiti Malaysia Pahang  

A study of the effectiveness of graphene oxides (GO) dispersed in water as a lubricant additive between tungsten carbide (WC) pin against stainless steel (SUS304) plate was carried out. A 0.1 wt.% GO was prepared and used as a lubricant under an applied load of 3 N for 20,000 friction cycles of reciprocating tribological testing. The results show that a GO dispersion with pH 3 provided the lowest friction coefficient, which was approximately 0.05. Worn areas on the wear track of the SUS304 flat plate and WC ball surface were also small. The increasing pH obviously affected the tribological properties, where the friction coefficient increased to approximately 0.10-0.20 in the steady state for pH 5, pH 7 and pH 9. Meanwhile, a GO dispersion with pH 10 was not able to provide good tribological properties for the tested materials. The observations on microscopic images revealed the formation of tribofilms on the wear tracks for low pH. The tribofilms caused reduction of the friction force and protected the plates from severe wear during the sliding tests.

DOI： 10.15282/ijame.13.1.2016.2.0262

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DOI： 10.18914/tribologist.61.6_393

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

Radio frequency-microelectromechanical system (RF-MEMS) switches, which use physical Ohmic contacts, are recently focused for high performance in the high-frequency ranges. Typically, the contact areas of the electrodes in RF-MEMS switches are less than 0.01 mm(2), and they generate just very low normal loads of less than 1 mN. The limited real contact area of the electrodes leads to high electrical contact resistances and wear on the switches. Carbon nanotube (CNT) films, formed with many vertically aligned CNTs on a silicon substrate, are one candidate electrode material for RF-MEMS switches. However, CNT films have a high electrical contact resistance with metals. In this study, precious-metal electroplating (Ag, Au, Pt, Rh, and Cu) on CNT films was performed to decrease the electrical contact resistances of the films and increase their wear resistances. The contact resistances of the electroplated CNT films as a function of normal loads up to 1 mN were measured by phi 2 mm Cu balls. In this study, the Ag-electroplated CNT film with a hydrogen annealing had the lowest electrical contact resistance of 0.10 Omega. Durability experiments of cyclic connection switching were conducted under direct applied voltages of 3 V or 10 V between the films and Cu balls, and with a load of 1 mN for 3 x 10(5) cycles. The electrical contact resistance of the Ag-electroplated CNT film with the hydrogen annealing was stable during this durability experiment.

DOI： 10.1299/mej.15-00346

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High-performance lubricating additives are desired in order to improve the properties of lubricating fluids. Recently, carbon nanomaterials such as fullerenes, carbon nanotubes, and carbon onions have been studied as lubricating additives for water and lubricating oils. However, the costs of these carbon nanomaterials are too high for practical use. On the other hand, graphene oxide (GO) is a carbon nanomaterial that consists of single atom thick sheets that possess a large number of oxygen functional groups. Since GO is synthesized from graphite using a chemical liquid process, the cost of GO is significantly lower than other carbon nanomaterials. In this study, the application and tribological properties of GO monolayer sheets as additives in water and poly-alpha olefin (PAO) were investigated. The dependence of the friction coefficient of GO-water dispersions on GO concentration (0.01-1.0 mass %) was investigated. In particular, GO-water dispersions with a concentration of less than 0.1 mass % demonstrated low friction coefficients. In this study, GO was simply dispersed in PAO using surfactant and intermediary solvents without the need for drying treatments. We found that the use of anionic surfactants in the GO-PAO dispersions was better than cationic surfactants in terms of the degree of wear observed. Specifically, GO-PAO dispersions that used an anionic surfactant with a GO concentration of 4 mass % had the smallest wear in this study. Moreover, friction coefficients were not decreased by the addition of GO in PAO. Finally, we found that intermediary solvents did not affect lubrication.

DOI： 10.1299/mej.15-00323

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Although fluorine-containing ionic liquids have excellent lubricity as liquid lubricants for steels, strong tribochemical reactions leading to severe wear are occurred during friction. Recently, it is reported that graphene oxide (GO) dispersed in water and oils exhibit good anti-wear property. In this study, in order to investigate anti-wear effect of GO in lubrication of fluorine-containing ionic liquids for steel, tribological properties of mixtures of GO with concentrations of 0.2, 2, and 10 mass% and an ionic liquid [BMIM][BF4]) were investigated on a steel surface. Under the pure ionic liquid lubrication, a strong tribochemical reaction occurred, resulting in corrosion wear. Under a GO-ionic liquid mixture lubrication with 0.2 mass% GO, wear was much lower than for the pure ionic liquid lubrication. Adding GO would inhibit the strong tribochemical reaction. However, wear was high with the 10 mass% GO-ionic liquid mixture. The GO-ionic liquid mixtures did not greatly decrease the friction coefficient.

DOI： 10.2474/trol.10.91

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We studied the effectiveness of diamond nanoparticles (DNPs) dispersed in water as a lubricant additive between stainless steel plates and sintered tungsten carbide (WC) balls. DNP dispersions with concentrations of 0.01, 0.1 and 1 wt.% were prepared and used as lubricants under a load of 1.88 N, for 240,000 friction cycles. High-friction coefficients of more than 0 3 were observed in an initial period. Then friction coefficients declined and stabilised at values of approximately 0.1. The steady-state friction coefficients were independent of the DNP concentration and lower than that for distilled water. In the initial period, wear of both the plates and ball was obvious. In the steady-state period, additional wear on the plates was a little; however, ball wear scars were clearly observed. The size of the ball wear scars decreased with decreasing the DNP concentration. It is likely that DNPs were embedded mainly in the stainless steel plates, and the embedded DNPs protected the plates and wore the balls in the steady-state period. Compared with the lubrication under distilled water, the friction coefficient and wear of the plate under the lubrication by the 0.01 wt.% DNP dispersion were lower, and the wear of the ball by this lubrication condition was not higher.

DOI： 10.1299/jamdsm.2015jamdsm0006

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：National Taiwan University  

DLC coatings are currently used in a wide variety of industrial fields because of their outstanding properties such as high hardness, high wear resistance, low friction and so on under oil lubrication as well as no lubrication. The tribological properties were compared with six types of DLC coatings: amorphous hydrogenated DLC (a-C:H), that doped with tungsten (a-C:H:W), that doped with silicon (a-C:H:Si) and hydrogen-free DLC (ta-C). Sliding tests were conducted under water lubrication at sliding velocities of 0.02 m/s and 0.1 m/s. DLC coatings showed low friction coefficient and excellent wear resistance. Friction coefficient and wear rate decreased with increasing sliding velocity. The effect of surface wettability and mechanical properties on tribological characteristic were investigated. Friction coefficient decreased as the contact angle increased. Hydrogen-free DLC-4 with the highest hardness showed the highest friction and a larger wear. Furthermore, DLC coatings deposited with interlayer showed longer lifetimes.

DOI： 10.6567/IFToMM.14TH.WC.OS18.019

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DOI： 10.18914/tribologist.59.09_577

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DOI： 10.18914/tribologist.58.11_832

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DOI： 10.1299/jamdsm.6.1

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

Under micronewton loads, the high frictions on carbon nanotube (CNT) films (with a friction coefficient of 1.7) were decreased to less than the noise level (which was roughly a friction coefficient of 0.05) by applying an oscillating motion to a cantilever on which a sliding ball was glued. This large decrease of the friction coefficient has been never observed in previous studies. The applied oscillating motion caused the twisting and bending oscillations of the cantilever, which applied the lateral and normal oscillating forces to the sliding ball. The friction force decreased with increasing the oscillating amplitudes of the twisting and bending forces, and the frequency dependences of the friction force reduction was observed.

DOI： 10.2474/trol.7.213

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In this study, steel rollers and gears were treated by the cavitation peening with processing times of 1 min and 5 min, and they were fatigue-tested using a roller testing machine and a gear testing machine. The surface hardness and the compressive residual stress of the rollers and gears were increased by the cavitation peening, while, the surface roughness of the cavitation-peened rollers and gears was almost the same as that of the non-peened ones. As a result of the fatigue tests, the fatigue strength of the test specimens were improved by the increase in surface hardness due to the cavitation peening, and those without the increase in surface hardness were not increased so much. The fatigue strength of the cavitation-peened test specimens was similar to that of the shot-peened ones obtained by the previous fatigue tests. This study revealed that the cavitation peening is expected to put to practical use in the improvement in fatigue strength of steel gears.

DOI： 10.1299/jamdsm.6.33

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Diamond-like-carbon (DLC) coating of thickness 3 and 10 mu M were developed with and without radical nitriding pretreatment on steel rollers and spur gear pair. The friction coefficient and wear amount were evaluated under sliding rolling contact condition in vacuum and under oil lubrication. Delamination of coatings was observed at the interface of the substrate. The wear resistance of coatings improved with the thickness of the coating. In vacuum both the roller and the gear pair of 10 mu m coating thickness with radical nitriding showed identical wear behavior. The radical nitriding seemed to enhance the life of DLC coatings. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.triboint.2010.07.005

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

The purpose of this study is to investigate the influence of peening on the rolling contact fatigue (RCF) life of steel rollers. First, steel rollers were treated by three types of peenings to ensure the same surface roughness of peened rollers. One is the cavitation peening (CP) used a cavitating jet in water with an injection pressure of 30 MPa, and the others are the fine particle peening (FPP) with a shot diameter of 0.1 mm and the normal shot peening (NSP) with a shot diameter of 0.3 mm. The surface hardness and the surface compressive residual stress of the steel rollers were increased by all the peenings. In particular, they were most increased by the FPP. On the other hand, the work-hardened depth due to the CP and the NSP was larger than that due to the FPP. As a result of the RCF tests, the RCF lives of the steel rollers were improved by all the peenings, and they were most improved by the NSP. Judging from the p_max - N curves and the [A(σ_y/√3 HV)]_max - N curves, the improvement in RCF lives due to the FPP depended heavily on the increase in surface hardness due to that, and the effects of the CP and the NSP on the RCF were equivalent under the same surface roughness and the same surface hardness. It follows from these that the surface treatment condition should be selected according to the rolling contact conditions and the failure modes of machine elements.

DOI： 10.1299/jmmp.6.478

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

In order to investigate the influence of different shot peenings on the rolling contact fatigue life of case-hardened steel, the thrust type rolling contact fatigue test was performed with a ball-on-disk contact tester. In this study, the case-hardened steel disks were treated by the fine particle peening with a shot diameter of 0.05 mm and the normal shot peening with a shot diameter of 0.30 mm. The surface hardness and the surface compressive residual stress of the test disks were increased by these peenings. On the other hand, the surface roughness of the test disks was increased by the normal shot peening, and was decreased by the fine particle peening. The rolling contact fatigue test showed that the rolling contact fatigue life of the test disks was improved by the fine particle peening, and was not improved by the normal shot peening. The rolling contact fatigue life of the test disks became longer as their surface roughness became smaller. Therefore, it follows from this that the fine particle peening, which can provide the increase in surface hardness and the decrease in surface roughness, is good for the increase in the rolling contact fatigue life of case-hardened steel.

DOI： 10.4028/www.scientific.net/AMM.86.645

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KOREAN SOC MECHANICAL ENGINEERS  

To investigate the influence of shot peening on the surface durability of powder-forged rollers, the case-hardened powder-forged rollers with a forging density of 7.5 g/cm(3) treated by the single shot peening and the double shot peening were fatigue-tested under a sliding-rolling contact condition. The surface roughness, the surface hardness and the surface compressive residual stress of the rollers were increased by the shot peening. In addition, the pores near the roller surface were deformed by the shot peening. The failure mode of all the test rollers was spalling due to subsurface cracking. The fatigue lives of all the test rollers were improved by the shot peening, and that of the test roller S08, which was shot-peened with the hardest steel shots in this experimental range, was especially improved. The surface durability of the test roller S08 was also most improved by the shot peening. Cracks became difficult to occur and propagate under the roller surface since the pores near the roller surface were deformed by the stronger shot peening. In this study, double shot peening, which generally restrains the increase in surface roughness, was not particularly effective for the improvement in the surface durability of the powder-forged rollers, because the influence of tangential force on fatigue was not always great in a case of subsurface cracking.

DOI： 10.1007/s12206-09-1161-2

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：KOREAN SOC MECHANICAL ENGINEERS  

The purpose of this study is to investigate the influence of tungsten carbide/carbon (WC/C) coating on the surface durability of case-hardened steel gear. Two kinds of WC/C coatings were deposited on the ground gear pair made of chromium molybdenum steel with carburizing and quenching. One is the conventional WC/C coating, and the other is WC/C coating with about 1 mu m CrN interlayer. Here, the WC/C-coated test pinion and the WC/C-coated one with CrN interlayer are represented by WT and ST, respectively. Non-coated test pinion is represented by NT. The surface roughness along the tooth profile direction of WT and ST was almost the same as that of NT. A spur gear test was carried out with an IAE power circulating type gear test rig under EP gear oil lubricating condition. The fatal failure mode of the test pinions was pitting due to surface cracking. The fatigue life of WT was longer than that of NT under a maximum Hertzian stress p(max)=1700 MPa. On the other hand, under p(max)=1900 MPa, that of WT was as long as that of NT due to the peeling occurrence of the coated layer. Under the comparatively low load condition without peeling occurrence, the surface roughness of WT decreased with the increasing number of cycles, and their fatigue life became longer than that of NT. On the contrary, in the case of ST, the peeling of the coated layer occurred at a comparatively early stage of the gear test, and the dedendum was worn by tens of micrometers. Therefore, in the case of ST, the effect of the WC/C coating disappeared at a comparatively small number of cycles.

DOI： 10.1007/s12206-009-1171-0

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

In order to examine the effects of the O-value and the hardness on the pitting fatigue life and the surface durability synthetically, data from 38 series of roller tests and 2 series of gear tests which were conducted under a sliding-rolling contact condition with various lubricating oils using various specimens with different hardness of HV170 to HV540 finished by various methods are considered in this paper. It is consequently clarified that the surface durability is proportional to the hardness and this tendency is changed by the surface roughness and the D-value, the relationship between the Dvalue and the pitting fatigue life N is not absolute with some dispersion even under the same hardness condition, the D-value at endurance limit, i. e., Dlim tends to increase as the hardness and the surface roughness increase, and as to an equation of σHIIM=aDlim 385 between the Hertzian stress at endurance limit σHlim and the D lim introduced by the defined equations of the Hertzian stress and the D-value, value of a tends to decrease as the hardness and the surface roughness increase. '.

DOI： 10.1299/kikaic.76.2325

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The purpose of this study is to investigate the effect of cavitation peening on the rolling contact fatigue life of steel gears. The steel rollers and gears cavitation-peened under different conditions were fatigue-tested using a roller testing machine and a gear testing machine. After the cavitation peening, the surface hardness and the surface compressive residual stress of the steel rollers and gears were increased. On the other hand, the surface roughness was not increased so much. As a result, the fatigue life of most cavitation-peened rollers and gears was longer than that of the non-peened ones. In particular, the fatigue life was significantly improved by using a modified nozzle for a high-speed water jet to obtain a greater peening effect. It is suggested from these that the cavitation peening is good for the increase in fatigue life of steel gears, because the peening effect is obtained with less increase of the surface roughness.

DOI： 10.2474/trol.3.116

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The rolling contact fatigue of crowned rollers made of bearing steel SUJ2 was investigated with a two-roller test machine under a sliding-rolling contact condition with oil lubricant. The nominal crowning radii of the rollers were 110mm, 90mm and 60mm. The roller was mated with a non-crowned roller or a roller with a concave crowning radius of 110mm. The contact pressure and subsurface stress were analyzed with three dimensional FEM. Within the applied load in this experiment no edge loading or minor edge loading occurred in the crowned rollers mated with the non-crowned roller and major edge loading occurred in the crowned rollers mated with the concave crowned roller. In case that no edge loading or minor edge loading occurred, the failure mode of the rollers were pitting caused by surface cracking and the rolling contact fatigue strength evaluated with the normal load increased with increasing crowning radius. In case that the edge loading was great, the failure mode of the rollers tended to be spalling caused by subsurface cracking and the influence of the crowning radius on the rolling contact fatigue strength was little.

DOI： 10.1299/kikaic.73.1222

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In order to elucidate the rolling contact fatigue characteristics of the newly developed bearing steel SBS1 principally under the quasi-high temperature, the washer and ball specimens made of SBS1 were tested at a temperature of 403 K and also at non-controlled temperatures under a rolling contact condition using a thrust bearing type rolling fatigue testing machine. This kind of test was performed also by using the conventional bearing steel SUJ2 for the comparison. For discussing these results about the rolling contact fatigue lives of the washers, the microstructural changes of the fatigue-tested washers and balls were observed around the depth where the orthogonal shear stress and the maximum shear stress become maximum. The soaking test was also conducted at a temperature of 453 K using the balls, and the changes of the hardness and the full width at half maximum with the increase of the soaking time was examined. It could be clarified from these investigations that the rolling contact fatigue life of the newly developed bearing steel SBS1 was much longer than that of the conventional bearing steel SUJ2 especially under the quasi-high temperature.

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The influence of the sprayed layer thickness on rolling contact fatigue of a thermally sprayed alumina ceramics with a nominal composition of Al(2)O(3)-2.3 mass% TiO(2) was investigated using a two-roller test machine under pure rolling contact condition with oil lubricant. The influence of undercoating of sprayed nickel-based alloy on rolling contact fatigue was also investigated. Thicknesses of the ceramics-sprayed layer of tested rollers were 0.2, 0.5 and 1.0 mm. The failure mode of sprayed rollers was spalling caused by subsurface cracking. In the case of sprayed rollers without undercoating, rolling contact fatigue strength of rollers with 0.2 mm thickness sprayed layer was the smallest. Rolling contact fatigue strength of sprayed roller with 0.2 mm thickness sprayed layer was improved by undercoating. In case the failure depth was small as compared with the thickness of sprayed layer, effect of undercoating on the rolling contact fatigue strength was little. The depths where the maximum values of subsurface shear stresses occurred, almost corresponded to the observed depth of spalling cracks. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.triboint.2006.01.013

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Recent rolling bearings have been used under the severe condition in many machines. For this trend, the vacuum melt to reduce the inclusion and some special heat treatments have been applied to the bearing steel for improving the rolling fatigue characteristics. While, the new development of bearing steel itself is required for the greater improvement in the fatigue characteristics. In this report, a newly developed bearing steel ball with rich amount of Si and Mo and the conventional bearing steel SUJ2 ball were fatigue-tested using a dynamic load type and a static load type rolling bearing fatigue testing machines. The rolling fatigue lives of these new and conventional steel balls were compared with each other, and were discussed considering the measured results of the hardness, residual stress, full width at half maximum and retained austenite during the fatigue process, and also of the initial carbide grain size, crush load and so on. It was consequently confirmed that the newly developed bearing steel ball has much longer rolling fatigue life comparing with the conventional one.

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The rolling contact fatigue of sprayed alumina ceramics with a nominal composition of Al(2)O(3)-2.3 mass% TiO(2) was studied with a two-roller test machine under a pure rolling contact condition with oil lubricant. The influence of undercoating of sprayed Ni-based alloy on the rolling contact fatigue was investigated. The failure mode of all sprayed rollers was spalling caused by subsurface cracking. The undercoating did not contribute to the improvement of the rolling contact fatigue life. The elastic modulus of the alumina sprayed layer evaluated with the nano-indentation method was around 85 GPa. The depths of the observed subsurface cracks corresponded approximately to the depths where the orthogonal shear stress or the maximum shear stress calculated with two-dimensional FEM became maximum. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.triboint.2005.07.038

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The influence of the sprayed layer thickness on the rolling contact fatigue of a thermally sprayed alumina ceramics with a nominal composition of Al_2O_3-2.3 mass%TiO_2 was investigated using a two-roller test machine under pure rolling contact condition with oil lubricant. The influence of undercoating of sprayed nickel based alloy on the rolling contact fatigue was also investigated. The thicknesses of the ceramics sprayed layer of the test rollers were 0.2, 0.5 and 1.0mm. The failure mode of the sprayed rollers was spalling caused by subsurface cracking. In case of the sprayed rollers without undercoating, the rolling contact fatigue strength of the rollers with 0.2mm thickness sprayed layer was the smallest. The rolling contact fatigue strength of the sprayed roller with 0.2mm thickness alumina sprayed layer was improved by undercoating. In case that the failure depth was small as compared with the thickness of the sprayed layer, the effect of undercoating on the rolling contact fatigue strength was little. The depths, where the maximum values of subsurface shear stresses occurred, almost corresponded to the observed depths of spalling cracks.

DOI： 10.1299/kikaic.72.1354

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The friction and wear characteristics of newly developed wear resisting stainless steel, which was designed for improving friction and wear characteristics, were investigated with ring-on-disk test apparatuses under oil lubricating condition and non-lubricating condition in air and in vacuum. The friction and wear behaviors were compared with those of JIS SUS420J2 stainless steel. In case under non-lubricating condition in air and in vacuum, both friction coefficient at room temperature and wear amount of the wear resisting stainless steel were smaller than those of SUS420J2. The extent of transference of wear debris was comparatively small in case of the wear resisting stainless steel. In case under oil lubricating condition, the scuffing of the wear resisting stainless steel was hard to progress and the wear amount was also small even after scuffing occurrence. The wear resisting stainless steel had the superior anti-scuffing characteristics.

DOI： 10.1299/kikaic.71.1376

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The rolling contact fatigue of crowned rollers made of bearing steel was investigated with a two-roller test machine under a sliding-rolling contact condition with oil lubricant. The nominal crowning radii of the rollers were 110, 90 and 60 mm. The roller was mated with a non-crowned roller or a roller with a concave crowning radius of 110 mm. In case that no edge load or minor edge load occurred, the failure mode of the rollers tended to be pitting caused by surface cracking and the rolling contact fatigue strength evaluated with the normal load increased with increasing crowning radius. In case that the edge load was great, the failure mode of the rollers tended to be spalling caused by subsurface cracking and the difference in the rolling contact fatigue strength was little.

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The rolling contact fatigue of a sprayed alumina ceramics with a nominal composition of Al_2O_3-2.3 mass%TiO_2 was studied with a two-roller test apparatus under pure rolling contact condition with oil lubricant. The alumina ceramics was prepared by plasma spray process. The influence of undercoating of sprayed Ni based alloy and surface sealing on the rolling contact fatigue was investigated. The failure mode of all sprayed rollers was spalling caused by subsurface cracking. Neither undercoating nor surface sealing contributed to the improvement of the rolling contact fatigue. The elastic modulus of the alumina sprayed layer evaluated with the nano-indentation method was around 85 GPa. The subsurface shear stresses were calculated with two-dimensional FEM analyses. The maximum values of orthogonal shear stress and maximum shear stress occurred within the spraved layer. The depths of observed subsurface cracks were generally deeper than those of the maxima of shear stresses.

DOI： 10.1299/kikaic.70.3331

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A gear test and a two-cylinder test were carried out under non-lubricating condition in high vacuum to investigate the friction and wear behaviors of electroless Ni based alloy plated gears in vacuum. The gear test results were compared with the two-cylinder test results. Three kinds of electroless Ni based alloy platings and two kinds of composite platings with dispersed particles were employed here. In case of the Ni-P alloy plated gear with dispersed PTEE particles, the wear was almost uniform along the tooth profile and the fluctuation of the dynamic load was small. In cases of the Ni-B alloy plating, the Ni-P-B alloy plating and the Ni-P alloy plating with dispersed BN particles, the wear of the gear pairs was large, while the wear of the cylinders was rather small. Though the wear in the two-cylinder test was much smaller than that in the gear test, the average friction coefficients in both the two tests were almost the same with each other.

DOI： 10.1299/kikaic.69.1417

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Investigation on friction coefficient under high pressure such as cold forging was carried out by pin-on-disk test. Pin specimens were made of chromium-molybdenum steel SCM415 as work material and disk specimens were made of four kinds of high speed tool steels and cemented carbide as die materials. Nominal stresses of 1000 to 167N/mm(2) were loaded on the sliding surface of pin. The surface of the disk specimens was finished by #240, #800 emery papers or lapping. Friction coefficient of #800 polished disk showed lower value than that of mirror finished one. PVD treatments had good effect of low seizure properties. Especially, DLC treatment was free from seizure. The friction coefficient of P/M high speed tool steel H which contains appropriate dispersed carbide was lower than that of homogeneous microstructure AISI S7. This paper reports the friction coefficient relative to combination of materials, surface finish, surface treatment and load of specimens.

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Investigation on friction coefficient under high pressure such as cold forging was carried out by press-in punch test. Work specimen was made of chromium-molybdenum steel SCM415, and punch specimens were made of four kinds of tool steels, and cemented carbide as a die materials. Punches were finished by #240, #800 emery papers or lapping. Four kinds of oils and a lubricant were examined about frictional characteristics. Press-in force versus press-in depth was measured by press-in punch test. Friction coefficient was tried to calculate by numerical calculus of press-in force. PVD treatments had good effect of low seizure properties. Especially, DLC treatment was free from siezure.

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Various surface modification methods have been employed in order to improve the tribological. performance of machine elements. In this work, electroless Ni-P alloy plating and sulfurizing treatments were employed, and the surface modified steel rollers and ball bearings were fatigue-tested under a pure or free rolling contact condition. The fatigue lives of both rollers and bearings were improved by these surface modifications. The contact pressure and subsurface stresses of the surface modified rollers and bearings were analyzed. The reason why the rolling fatigue strengths of surface modified rollers and bearings were higher than those of the non-coated ones would be due to the smaller contact pressure and subsurface stresses by the smaller elasticity as well as the conformity of the plated layer. (C) 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0301-679X(02)00068-3

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Spur gear test was carried out under non-lubricating condition in high vacuum of the order of 10(-4) Pa at room temperature to investigate the wear and friction performances of electroless Ni alloy platings. Three kinds of electroless Ni alloy platings; electroless Ni-P alloy plating, electroless Ni-B alloy plating and electroless Ni-P-B alloy plating, and two kinds of composite platings; electroless Ni-P alloy plating with PTFE particles and electroless Ni-P alloy plating with BN particles, were employed. The influences of the composition and the dispersed self-lubricated particles in the electroless Ni alloy platings on the tribological performance were examined. In addition the gear test results were compared with the roller test results obtained under about the same maximum Hertzian pressure.

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DOI： 10.5988/jime.36.225

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The bulk temperature rise was studied when a moving heat source with variational heat quantity was applied repeatedly at regular intervals to the surface of an isotropic and homogeneous rectangular shaped body used as a model of a spur gear tooth. The effect of radiation at the inner surface of a boss on the bulk temperature rise is reduced as the distance between the inner surface of the boss and the working tooth flank is increased. The bulk temperature rise is almost inversely proportional to the heat supply interval. The size of the heat supply region and the moving direction of the heat source scarcely affect the bulk temperature rise. in a |νν^^-| range of not less than 1000, the bulk temperature rise is not affected by the moving velocity of the heat source, and the approximate bulk temperature rise can be obtained by dividing the temperature rise of the working tooth flank due to a stationary heat source by the number of teeth.

DOI： 10.1299/jsme1987.30.337

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The influence of tip interference on scoring load capacity was studied using gears having tooth profile wear due to scoring on the approach side. The results were compared with those obtained with gears having no profile wear from the viewpoints of scoring load and scoring temperature, taking the lubrication state on the working flank into consideration. The tip interference on the approach side should be reduced because, unlike on the recess side, it diminishes the scoring load capacity. In the mixed lubrication state, the working flank bulk temperature is suitable as an index for calculating the scoring load capacity of a spur gear pair. The scoring temperature on the cylinder just before seizure in two-cylinder tests, provided that the specific sliding and the sliding velocity at the end of gear meshing are taken into account.

DOI： 10.1299/jsme1987.30.1144

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Concerning the scoring resistance of the gear drive, the effects of the load intensity fluctuation on the anti-seizure capacity of a gear base oil were examined by two-cylinder tests at a high specific sliding considering the interference among projections. The frequency of interference among projections increases with an increases in specific sliding. Though the frequency in the heavy load intensity sector is higher than hat in light one. The effects of the load intensity difference on the frequency in a higher specific sliding range are smaller than those in a lower one. The seizure tends to take place in the heavy load intensity sector where the frequency of interference among projections and the bulk temperature are high. The load intensity fluctuation does not affect the anti-seizure capacity of the gear base oil. This is because there is affect the anti-seizure capacity of the gear base oil. This is because there is little difference between the lubrication states in both load intensity sectors.

DOI： 10.1299/jsme1958.29.2703

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Concerning the scoring resistance of the gear drive, the effects of the load intensity fluctuation on the state of interference among projections were examined for a gear base oil using a two-cylinder test rig. The frequency of interference among projections in the heavy load intensity sector is higher than that in the light one. Under rolling contact condition, the frequency of interference among projections increases a little as the load is increased. Under sliding-rolling contact condition, the frequency of interference among projections is higher than that under rolling contact condition. The frequency increases as the elastohydrodynamic lubrication film thickness is decreased due to the outer surface bulk temperature rise of the cylinder as the result of a load increase. Under sliding-rolling contact condition, the change in surface roughness in the heavy load intensity sector is greater than that in the light one.

DOI： 10.1299/jsme1958.29.2696

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DOI： 10.1299/jsmecs.2021.59.04c4

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DOI： 10.1299/jsmecs.2021.59.03c1

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DOI： 10.1299/jsmecs.2021.59.05c2

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DOI： 10.1299/jsmecs.2021.59.05b2

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DOI： 10.18914/tribologist.61.2_116

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In order to examine the sealing mechanism of a connection with a metal gasket, the sealing test according to JIS B2490 and FEM analysis were carried out. The dimensions of platen used in the test are according to JIS B 2490 and the metal gasket types are chosen as metal flat and ring joint gasket. The material of the gaskets was aluminum. The ring joint gasket types are chosen as octagonal and oval. The effect of internal pressure on the sealing performance of connection with the metal flat gaskets was measured. The relationship between the gasket compression stress and amount of leakage through inter faces on the metal flat gasket was obtained. And also, the relationship between compression load and amount of leakage through inter faces on the ring joint gaskets was obtained. The von Mises stress distributions on the interface on the metal gaskets were calculated using FEM. Using the results of sealing test and FEM, it was suggested that the sealing performance was improved, when the von Mises stress more than the gaskets material of the yield stress adequately. Furthermore, it was suggested experimentally that the ratio of the maximum of von Mises stress in the gaskets material of yield stress was 1.015.

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Recently it is important to reduce the car weight for fuel consumption improvement. One of the solutions is to exchange materials from steel to light weight materials. In this case, the bolted joints with dissimilar materials sometimes are needed. When temperature change occurs on the bolted joints, expansions of two clamped parts are different due to different coefficient of linear thermal expansion. And that causes the sliding force on the contact surface between two clamped parts. In this study, the deformations and the stress distributions under temperature change are analyzed by FEM for the bolted joints that consist of the rectangular aluminum plate, the steel plate and two bolts. Finally, comparisons in the sliding force between the simplified calculations by the spring models and FEM analyses are conducted for several dimensions of the plates.

DOI： 10.1299/jsmemecj.2015._S1130106-

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Press machine with a differential rotary to linear conversion mechanism was manufactured in order to evaluate the positioning performance of a punch. This differential rotary to linear conversion mechanism consisted of two rotary shafts, a rotation/translation shaft, three spur gears and a connecting block. A punch was attached to the end of the rotation/ translation shaft. In the positioning accuracy test of the punch, the positioning accuracy of the press machine was equivalent to that of the feed screw mechanism with a ball screw. In the input-output characteristics test, the press machine had superior input-output characteristics compared with the feed screw mechanism. Lastly, V bending work could be done by the press machine developed in this study.

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Because of light weight and high power of transmission, carburized and quenched gears are used as power transmission gear. Surface durability of carburized and quenched gears has been related with their tooth surface properties. The influence of abnormal carburized layer on the surface durability, however, has not been clarified. In this study, tested pinions were of two types: gear carburized and quenched after grinding, and gears carburized and quenched before grinding with two different surface roughness. In case of gears with equivalent surface roughness, the surface durability of the gear with abnormal carburized layer was longer than or almost the same as those without abnormal carburized layer. This would be because the abnormal carburized layer at the edge of tooth surface was worn during the fatigue tests.

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In order to investigate the influence of tooth surface form on fatigue strength of steel gears, the case-hardened steel gears with non-ground tooth surfaces, ground tooth surfaces and crowned ground tooth surfaces were fatigue-tested using a gear testing machine. In the fatigue tests, the surface failure of the gear with a crown radius of 300 mm started to occur in the center of the tooth surfaces, and that of the gears with non-ground and ground tooth surfaces started to occur at the edge of the tooth surfaces. The fatigue strength using Hertzian contact stress of the gear with a crown radius of 300 mm was the highest, followed by those of the gear with ground tooth surfaces, the gear with a crown radius of 600 mm and the gear with non-ground tooth surfaces. On the other hand, the fatigue strength using normal load of the gear with ground tooth surfaces was the highest, and those of the other gears were almost the same. Therefore, it was found that the fatigue strength using Hertzian contact stress of the steel gears depends heavily on a crown radius of tooth surface, and that using normal load has little influence on it in this experimental range.

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The problems of oil lubricants in waste and maintenance management are crucial for cost and environment. Water with less harmful to environment is suitable as a candidate lubricant to replace oil lubricants. However, water is lack of viscosity, which leads to high friction and severe wear between the sliding materials. Graphene Oxide (GO) is single layer graphite with oxygen functional groups and easy to be dispersed in water. In this study, the effect of friction reduction by water dispersed GO has been evaluated with different sliding materials. The friction coefficients between SUS304 substrate vs. SUS304 ball and SUS304 substrate vs. tungsten carbide (WC) ball were approximately 0.05. Severe wear was apparent on the SUS304 ball surface slid in the GO dispersion; however, only small wear was observed on the WC ball surface after friction test in the GO dispersion.

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Water lubrication, which uses water as lubricating fluid, has many advantages such as cost, environment, high thermal conductivity, and so on. However water has low lubricating property for steel materials. In this study, tribological property of nanodiamond, which is a few nanometer size diamond, as a water-based lubricant additive has been investigated between SUS304 ball -SUS304 plate and sintered tungsten carbide (WC) ball - SUS304 plate. It has found that adding nanodiamond in water can notably improve the water lubrication property such as the very low friction coefficient for the WC ball-SUS304 plate friction and low wear on the WC ball. However, friction forces and wears for the SUS304 ball-SUS304 plate was increased by adding nanodiamond.

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In this study, nanodiamond (ND)-electroless Ni plating composite coating was synthesized for high wear resistance and low friction. The ND-Ni plating composite coating was prepared from electroless Ni plating solution dispersing diamond nano particle (DNP) on S50C substrate. Heat treatment to increase hardness of electroless Ni plating was conducted in this coating. Tribological properties of the ND-Ni plating composite coating was investigated under three lubricant conditions (no lubrication, water lubrication and 1wt.% DNP dispersion). Under the DNP dispersion, the friction coefficient of ND-Ni plating composite film and Ni plating coating were lower than other conditions. Severe wears after the friction tests were observed on the ND-Ni plating composite coating under no lubrication, however only small protrusion of the composite film tested under the DNP dispersion was worn.

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Next generation wireless communication will be required to use in high frequency range (3-5 GHz), however semiconductor switch isn't having enough performance in the high frequency range. Radio Frequency-Micro Electro Mechanical Systems (RF-MEMS) switch (small mechanical switch) is recently focused for high performance in the high frequency range. There are problems of durability and adhesion on the contact materials of this device. Carbon nanotube (CNT) film has good wear resistance, very low adhesion and very low electrical resistance which are very useful to RF-MEMS switch. On the other hand, CNT film shows high electrical contact resistance. We attempted synthesis of metal plating on CNT film as reducing method of electrical contact resistance in this study. Fiber structure was observed in composite plating CNT film. Electrical resistance of the composite materials were 520.6Ωm measured by four probe method, and electrical contact resistance was about 3Ω with a load of 5mN by two probe method.

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In order to investigate shot peening on rolling contact fatigue lives of bearing steel, fatigue tests were performed with a thrust testing machine and a roller testing machine. The disks and rollers were treated by shot peening with a shot diameter of 0.05mm. The surface hardness and the surface compressive residual stress of the test specimens were increased by the shot peening. The rolling contact fatigue lives of the test specimens treated by the shot peening were longer than that of the non-peened test specimens. The rolling contact fatigue lives of the disk specimens were improved by the increase in surface hardness due to the shot peening.

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DOI： 10.1299/jsmecs.2013.51._404-1_

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Foreign object damage is attributed to dents formed by foreign objects such as debris and wear particles. It is important to clarify the behaviors of dent formation and stresses on contact surfaces in order to investigate the influence of foreign object damage on surface durability. Plastic deformation and formation of crown shape dent on contact surface were analyzed with elasto-plastic FEM analysis. A semispherical foreign object with a diameter of lOOμm was pressed against an elastic-perfectly plastic solid surface with a yield stress of 800 MPa or 1600 MPa Dent formation, crown height, contact pressure, and subsurface stress calculated with rigid foreign object were compared with those with elastic-perfectly plastic one.

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In this study, sintered and powder-forged rollers and gears with different densities and nickel contents were fatigue-tested using a roller testing machine and a gear testing machine in order to elucidate their fatigue strength. These experimental results were compared with the results of conventional steel ones. The hardness near the surface of the test specimens with higher nickel content was smaller than that of the other ones. The pores in the sintered rollers became smaller and were disappeared by the hot forging. The fatigue strength of the sintered rollers and gears was the lowest in this experimental range. The fatigue strength of the powder-forged rollers and gears was slightly lower than that of the steel ones. The fatigue strength of the test specimens increased as their density increased, and was hardly influenced by the nickel content in this experimental range. It was clear that the fatigue strength of the sintered and the powder-forged rollers and gears was proportional to the hardness for each pre-alloyed metal powder.

DOI： 10.1299/jsmemdt.2012.12.103

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Test model with three precision ball screws and three spur gears was manufactured in order to evaluate the positioning accuracy and the position keeping performance under heavy load by differential rotary to linear conversion mechanism. In the positioning accuracy test under a load of 515 N, the positioning accuracy of the test model was higher than that of the feed screw mechanism. In the position keeping performance test under a load of 515 N, it was confirmed that the test model had a position keeping performance for 600 s. These results revealed that the differential rotary to linear conversion mechanism had the positioning accuracy and the position keeping performance under heavy load.

DOI： 10.1299/jsmermd.2012._2P1-E06_1

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The purpose of this study is to investigate the effect of peening on the fatigue life of steel rollers. First, steel rollers were treated by three types of peenings to ensure the same surface roughness of peened rollers. One is the cavitation peening (CP) used a cavitating jet in water with an injection pressure of 30 MPa, and the others are the fine particle peening (FPP) with a shot diameter of 0.1 mm and the normal shot peening (NSP) with a shot diameter of 0.3 mm. The surface hardness and the surface compressive residual stress of the steel rollers were increased by all the peenings In particular, they were most increased by the FPP While, the work-hardened depth due to the CP and the NSP was larger than that due to the FPP. As a result of the roller tests, the fatigue lives of the steel rollers were improved by all the peenings, and they were most improved by the NSP. Judging from the P<max>-N curves and the [A(σ_y/Hv)]_<max>-N curves, the improvement m fatigue lives due to the FPP depended heavily on the increase in surface hardness due to that, and the effects of the CP and the NSP on the rolling contact fatigue were equivalent under the same surface roughness and the same surface hardness.

DOI： 10.1299/jsmemecj.2012._S112021-1

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DOI： 10.1299/jsmecs.2011.49.235

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Differential rotary to linear conversion mechanism with three precision ball screws and three spur gears were designed in order to evaluate the positioning accuracy and the input-output characteristics under the applied output load. In the positioning accuracy test, the positioning accuracy of this mechanism was almost equivalent to the accuracy of the precision ball screw employed in the test model. In the input torque-output load conversion test, the output load per unit input torque of this mechanism was larger than that of the feed screw mechanism. These results revealed that the differential rotary to linear conversion mechanism with three precision ball screws and three spur gears has the characteristics of both high positioning accuracy and excellent input-output conversion efficiency.

DOI： 10.1299/jsmermd.2011._2A2-J11_1

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DOI： 10.1299/jsmecs.2010.48.149

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The rolling contact fatigue test was conducted with thermal refined SCM and SNCM rollers with a hardness around HV350. The failure mode of all rollers was pitting caused by surface cracking. The surface hardness of rollers after test was increased by work hardening. The rolling contact fatigue strength increased with increasing surface hardness after test. The plastic deformation at the contact edge was discussed with the misaligned roller test. The strength of misaligned roller was the lower. The portion where the pitting failure occurred was not at the contact edge but toward the center of contact width. The plastic deformation at the contact edge could occurred at rather early stage of the test.

DOI： 10.1299/jsmemdt.2010.10.205

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Rotary to linear conversion is one of important mechanisms and has been widely used in various mechanical systems. We designed a new mechanism for rotary to linear conversion, which can provide linear output mechanically by using both screws and gears, and will be adequate for the both accurate positioning and high capacity. In this study, the compact mechanism designed for retrofit into mechanical devices was manufactured in order to investigate its fundamental performance. In the positioning accuracy test, the positioning accuracy of this mechanism was superior to that of a feed screw employed a precision ball screw. In the load output test, the load output of this mechanism was larger than that of a precision ball screw under some input torque condition.

DOI： 10.1299/jsmemecjo.2010.4.0_175

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DOI： 10.1299/jsmecs.2010.48.151

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DOI： 10.1299/jsmecs.2010.48.155

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DOI： 10.1299/jsmecs.2009.47.303

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Two kinds of WC/C coatings were deposited on the polished surface made of chromium molybdenum steel with carburizing and quenching. One is conventional WC/C coating and the other is WC/C coating with about 1μm CrN interlayer. The WC/C coatings were scratch-tested, and friction coefficient, critical load, and peeling behavior were evaluated. The friction coefficient of WC/C coatings were about a half of that of non-coated specimen. The critical load of WC/C coatings was independent on the CrN interlayer. Although the failure of substrate was negligible in the WC/C coated specimen without the interlayer, that was comparatively large in the WC/C coated specimen with the CrN interlayer. The amplitude of AE signal was large in the WC/C coated specimen with the CrN interlayer. While the CrN interlayer would improve the adhesion between the WC/C coating and the substrate, the large adhesion would negatively affect to the wear of the substrate ; the substrate was simultaneously removed with the peeling of the WC/C coating

DOI： 10.1299/jsmemecjo.2009.4.0_173

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DOI： 10.1299/jsmecs.2009.47.323

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While both friction and wear are small in an aerostatic guide whose bearing surfaces are separated by an air film, the stiffness is rather small. Porous materials are frequently used as a restrictor to improve stiffness in an aerostatic guide. In this study a partially porous ceramics, whose boundary between the porous part and the fine part was seamless and of which the porosity and the pore size were able to be controlled flexibly, was applied to the aerostatic guide. The fundamental static characteristics of the aerostatic guide made of the partially porous ceramics were, evaluated. In addition, electroless plating was posited onto the porous ceramics surface for the purpose of obtaining high static stiffness, and the effect of plating on the static stiffness was examined. The influence of deflection of porous ceramics on static characteristics of aerostatic guide was also evaluated. The minimum clearance at the maximum dimensionless static stiffness varied little with the deflection of porous ceramics. The maximum dimensionless static stiffness was decreased by the deflection of the porous ceramics. The maximum dimensionless static stiffness could be evaluated with the ratio of the deflection to the apparent clearance. Even in the case of the non-plated ceramics, the maximum dimensionless static stiffness was around 0.4. In the case of the plated ceramics, the flow rate decreased by 1/10 or less and the clearance decreased by approximately 1/3. Consequently, high stiffness was obtained by the plating. The partially porous ceramics employed in this study would be able to be applied to aerostatic guides. © Institution of Engineers Australia, 2008.

DOI： 10.1080/14484846.2008.11464555

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In order to investigate the effect of cavitation peening on surface durability of steel gears, the case-hardened steel rollers and gears cavitation-peened under different conditions were fatigue-tested using a roller testing machine and a gear testing machine. The hardness and the compressive residual stress of the test rollers and gears were increased by the cavitation peening. On the other hand, their surface roughness was not increased so much. In the roller tests, the fatigue life of all the cavitation-peened rollers was longer than that of the non-peened roller. In the gear tests, the surface durability of the test pinions was improved by the cavitation peening. Judging from the relationships between the maximum stress amplitude and the surface roughness, it was clear that the surface durability of steel gears was improved by the increase in surface hardness due to the cavitation peening with little influence of surface roughness.

DOI： 10.1299/jsmemdt.2008.8.89

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DOI： 10.1299/jsmecs.2008.46.361

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DOI： 10.1299/jsmecs.2008.46.359

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DOI： 10.1299/jsmecs.2008.46.337

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The purpose of this study is to investigate the influence of shot peening on the surface durability of sintered powder metal rollers. The test rollers employed in this study were made of the sintered material with a density of 7.01g/cm^3. The test rollers were shot-peened under different conditions. The surface roughness and the compressive residual stress of all the rollers were increased by the shot peening. On the other hand, the surface hardness was not increased. The rolling contact fatigue test of the rollers was performed under a sliding-rolling contact condition using a roller testing machine. The failure mode of the test rollers was spalling due to subsurface cracking. A crack occurred at a pore below the roller surface. Judging from the p_<max>-N curves, the surface durability of the shot-peeened rollers was smaller than that of the non-peened roller.

DOI： 10.1299/jsmemdt.2008.8.93

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DOI： 10.1299/jsmecs.2008.46.357

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DOI： 10.1299/jsmecs.2008.46.351

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DOI： 10.1299/jsmekyushu.2008.71

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DOI： 10.1299/jsmekyushu.2008.51

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DOI： 10.1299/jsmecs.2007.45.349

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In order to investigate the influence of shot peening on the surface durability of steel rollers, the steel ones treated by single and double shot peenings were fatigue-tested using two cylinders testing machine under a sliding-rolling contact condition. The hardness and the compressive residual stress of the test rollers were increased by shot peening. Their surface roughnesses were also increased by shot peening, and the surface roughness of the double shot-peened rollers was smaller than that of the single shot-peened ones. The cause of failure of all the test rollers was the spalling due to the subsurface cracking. The surface durability of the shot-peened rollers was larger than that of the non-peened roller. In particular, that of the double shot-peened rollers was the largest in this study.

DOI： 10.1299/jsmempt.2007.35

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In order to evaluate the influence of artificial defects (holes) on rolling contact fatigue strength of steel rollers, the steel rollers with artificial defects were contact fatigue-tested under a sliding-rolling contact condition. The crack propagation behavior was investigated. The rolling contact fatigue strength of rollers with artificial defects was smaller than those of rollers with non-artificial defect. In the case of rollers with artificial defects, cracks occurred in the vicinity of holes. The initial crack propagated from the hole was parallel to the roller surface. Then the crack propagated in a range of 20 degrees -45 degrees for the crack that progressed in parallel with the surface. To examine what kind of subsurface stress affected the crack, internal stresses around hole were calculated with FEM. The factor that affected the initiation of cracks would be the maximum shear stress τ_<max>, and the factor that affected the propagation of cracks would be the orthogonal shear stress τ_<yz>.

DOI： 10.1299/jsmempt.2007.43

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In order to investigate the effect of cavitation shotless peening on fatigue strength of steel gears, the case-hardened steel rollers and gears cavitation shotless peened under different conditions were fatigue-tested using a roller testing machine and a gear testing machine. The hardness and the compressive residual stress of the test rollers and gears were increased by cavitation shotless peening. On the other hand, their surface roughness was not increased so much. In the fatigue tests, the fatigue life of most cavitation shotless peened rollers and gears was longer than that of the non-peened roller and gear. In particular, the fatigue life of cavitation shotless peened rollers and gears was significantly improved by using a modified nozzle for a high-speed water jet to obtain a greater peening effect. Therefore, it was found that the cavitation shotless peening is good for the increase in fatigue strength of steel gears.

DOI： 10.1299/jsmempt.2007.23

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Rolling contact fatigue test with three kinds of lubricating oil was carried out in order to clarify the influence of viscosity characteristics of lubricating oil on rolling fatigue strength of steel roller. Each lubricating oil was different in viscosity of base oil and blending quantity of the viscosity index improver. In case of the test under the lubricants with equivalent kinematic viscosity, the rolling contact fatigue life depended on the viscosity of the base oil and was longer in case that the base oil of the lubricant had the higher kinematic viscosity. In case of the rolling fatigue test under lubricant made from same base oil, the rolling contact fatigue life was longer in case of the rolling fatigue test under the lubricant with higher kinematic viscosity, Small spot marks with relatively high roughness would occur by non-destructive scuffing.

DOI： 10.1299/jsmempt.2007.90

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DOI： 10.1299/jsmecs.2007.45.367

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DOI： 10.1299/jsmecs.2007.45.361

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Friction and wear performance of plasma CVD Diamond-Like Carbon coating deposited on a spur gear and a roller made of stainless steel was investigated. A spur gear test and a roller test were carried out under non-lubricating condition in high vacuum. A roller test was also performed under oil lubrication. The wear performance of the thick DLC coating was comparatively superior. The radical nitriding pretreatment was effective against wear of DLC coating. The wear performance of DLC coating on the gear was similar to that on the roller. Though the wear in the roller test was much smaller than that in the gear test, the specific wear amounts in both the two tests were almost the same with each other.

DOI： 10.1299/jsmemecjo.2006.4.0_189

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DOI： 10.1299/jsmecs.2006.44.359

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A rolling contact fatigue test was carried out under a traction oil lubricating condition and the test result was compared with that under a turbine oil lubricating condition. The minimum film thicknesses under both lubricating conditions were almost equal. The failure mode of both lubricating conditions was pitting caused by surface cracking. The rolling contact fatigue strength under the traction oil lubricating condition was greater than that under the turbine oil lubricating condition. The cracks observed on the roller surfaces tested under the traction oil lubricating condition were the longer along the axial direction of the rollers.

DOI： 10.1299/jsmemdt.2006.6.203

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DOI： 10.1299/jsmecs.2006.44.351

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DOI： 10.1299/jsmecs.2006.44.343

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DOI： 10.1299/jsmecs.2005.43.295

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DOI： 10.1299/jsmecs.2005.43.297

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DOI： 10.1299/jsmecs.2004.42.415

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In order to investigate the influence of dispersed particles on friction and wear of electroless composite plating, two-roller test was carried out under oil lubricating condition and in vacuum. The dispersed particles were PTFE and SiC. In vacuum, the friction coefficient decreased and the wear increased, with increasing content of dispersed particles. Under oil lubrication, the friction was low and the wear increased at comparatively early stage in only the case of a particle-content of 30%. Stresses in the plated layer were calculated with FEM. The maximum Mises stress in the plated layer increased with increasing content of dispersed particles.

DOI： 10.1299/jsmempt.2004.313

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This paper describes about influence of crowning on rolling contact fatigue of steel roller. The edge load at the contact edge and subsurface shear stresses were calculated with FEM. In case that no edge load or minor edge load, the rolling contact fatigue strength of rollers evaluated with the normal load increased with increasing the crowning radius. The stressed volume varied widely with the crowning radius. The rolling contact fatigue strength should be evaluated from the point of view of the stressed volume.

DOI： 10.1299/jsmempt.2004.182

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DOI： 10.1299/jsmecs.2004.42.413

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DOI： 10.1299/jsmecs.2004.42.403

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The friction and wear characteristics of newly developed stainless steel with dispersed precipitations, which was designed for improving friction and wear characteristics, were investigated with ring-on-disk test apparatuses under non-lubricating condition in air and in vacuum. The friction and wear behaviors were compared with those of JIS SUS420J2 stainless steel. Both friction coefficient and wear amount of the stainless steel with dispersed precipitations were smaller than those of SUS420J2. The extent of transference of wear debris was comparatively small in case of the stainless steel with dispersed precipitations. The stainless steel with dispersed precipitations had the superior friction and wear characteristics.

DOI： 10.1299/jsmemecjo.2004.4.0_109

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The authors examined friction and wear characteristics of electroless Ni based alloy platings under oil lubricating condition with ring-on-disk test machine. Electroless Ni-P alloy plating, electroless Ni-B alloy plating and electroless Ni-P-B alloy plating were employed. In case of the combination of the electroless Ni-B alloy plating and the electroless Ni-P-B plating the wear occurred in the lowest contact pressure. The friction behavior was the most stable in case of the combination of the electroless Ni-B alloy plating and the electroless Ni-P alloy plating. The friction coefficient of the self-mated electroless Ni-P-B plating was small, while the wear was comparatively large.

DOI： 10.1299/jsmemecjo.2003.4.0_127

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In order to examine the possibility of applying newly developed porous fine ceramics to aerostatic guides, the static stiffness of an externally pressurized gas thrust bearing made of the porous fine ceramics was investigated. The area and center-to-center distance of pores were analyzed with image processing technique. 60% of the pores of the tested fine ceramics were of 40μm in diameter and the mean center-to-center distance was 85.4μm. The dimensionless static stiffness of the tested porous fine ceramics was 0.45-0.6 at a bearing clearance around 5μm. The tested porous fine ceramics would be applied to aerostatic guides.

DOI： 10.1299/jsmemecjo.2003.4.0_199

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In order to investigate friction and wear characteristics of the thermal diffused Sn plated stainless steel in vacuum, ring on disk tests were performed. In case of the tests in vacuum the friction coefficient at high temperature was slightly smaller than that at room temperature, while the specific wear rate at high temperature was greater than that at room temperature. In case of the tests in vacuum the friction behavior was stable and the wear was small after the wear depth was equivalent to the thickness of the modified layer. On the contrary both the friction coefficient and the wear were increased with increasing sliding distance and the wear exceeded the modified layer.

DOI： 10.1299/jsmemecjo.2003.4.0_129

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DOI： 10.1299/jsmecs.2003.41.285

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DOI： 10.1299/jsmecs.2002.181

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DOI： 10.1299/jsmecs.2002.40.365

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Roller test and ring/disk test were carried out under non-lubricating condition in high vacuum to investigate the tribological performance of particle dispersed composite platings based on electroless Ni-P alloy. Three kinds of composite platings, in which PTFE particles, BN particles, and SiC particles were dispersed, were employed. The wear rate of both plated layers with BN particles and with PTFE particles increased with increasing content of dispersed particles. The wear rate of the layer with PTFE particles was greater than that with BN particles. The influence of elastic modulus of dispersed particles on stresses in the plated layer was investigated with FEM analysis. The maximum values of Mises stress in the plated layer increased with increasing particle content and with decreasing elastic modulus of particles. The wear behavior obtained in the experiment could be well explained by the calculated stress field.

DOI： 10.1299/jsmemdt.2002.2.203

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DOI： 10.1299/jsmecs.2002.40.363

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DOI： 10.1299/jsmecs.2001.39.323

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DOI： 10.1299/jsmecs.2001.39.327

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DOI： 10.1299/jsmecs.2001.39.325

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DOI： 10.1299/jsmecs.005.1.321

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DOI： 10.1299/jsmecs.005.2.203

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Surface modified rollers by electroless Ni-P alloy plating and sulfurizing were fatigue-tested under a pure rolling contact condition. The fatigue lives of both surface modified rollers were longer than that of the non-coated rollers and the fatigue strength of the sulfurized rollers was the highest. The influence of elastic modulus of a plated layer on the contact pressure and the subsurface stresses was examined with numerical analyses. The contact pressure and the subsurface stresses of a roller covered with a plated layer, whose elastic modulus was smaller than that of the substrate, were smaller than those of a non-coated roller, especially at the edge of the contact width. The conformity by the wear of the plated layer led to the reduction of the contact pressure and the subsurface stresses at the edge of the contact width. The reason why the fatigue strength of the surface modified rollers were greater than that of the non-coated rollers could be due to the smaller contact pressure and the smaller subsurface stresses. © 2000, The Japan Society of Mechanical Engineers. All rights reserved.

DOI： 10.1299/kikaic.66.275

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To clarify the friction and wear characteristics of surface modified rollers in vacuum, two cylinder test was carried out under non-lubricating condition in high vacuum less than 2 × 10^<-3> Pa. Thermal diffusion after Sn plating (Sn), electroless Ni-P plating (Ni-P) and sulfurizing were employed here. Friction coefScient of the surface modified rollers was smaller than that of non-coated rollers. The initial friction coefficient of Sn plated rollers increased under low contact pressure, where wear particles were transferred onto the frictional surface, while the friction coefficient decreased when surface modified layer worn uniformly. The sulfurizing contributed to the reduction of the initial friction. The friction behavior of Ni-P plated rollers indicated the most stable in all test rollers. In addition, the relation between the test results in the two cylinder tests and the previous gear tests in high vacuum using the same surface modification treatment as employed in these two cylinder tests was evaluated. The initial friction in the two cylinder test was greater than that in the gear test in the cases of non coat, Sn and Ni-P. However, where sliding distance was large enough, the friction behavior in the gear test was similar to that in the two cylinder test.

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In order to investigate the friction and wear characteristics of surface modified spur gears made of stainless steel SUS440C in high vacuum, gear tests were carried out under non-lubricating condition in vacuum to be on the order of 10^<-4> Pa. In addition, dynamic load on spur gear teeth with surface modified layer was evaluated. Electroless Ni-P alloy plating (Ni-P plating), sulfurizing and Sn plating with thermal diffusion (Sn plating) were employed. From the gear tests, the following results were obtained. (1) The friction coefficient of the surface modified gears was smaller than that of the non-coated gears. (2) The initial friction of Sn plated gear increased under low pressure and low rotational speed conditions. After Sn plated layer wore uniformly, the friction coefficient was the smallest by the lubricating effect of thermally diffused layer of Sn. (3) The sulfurized layer contributed to the reduction of initial friction. However, the friction behavior of sulfurized gear was the same as that of non-coated gears, after the sulfurized layer wore completely. (4) Wear amount and tooth profile error of Ni-P plated gears were the largest of all the test gears.

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DOI： 10.1299/kikaic.65.2034

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DOI： 10.1299/kikaic.65.1661

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Authorship：Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The influence of the surface modification treatment on the rolling contact fatigue and the scuffing capacity of rollers was examined by two cylinder test under oil lubrication. The surfaces of test rollers were modified by the electroless Ni-P alloy plating and the sulfurizing. The rolling contact fatigue strength and the scuffing capacity of the surface modified rollers were larger than those of the non-coated rollers. In the fatigue test the failure mode of both the surface modified rollers and the non-coated rollers was the spalling caused by subsurface cracking. The friction coefficient of the Ni-P plated rollers was smaller than that of the non-coated rollers, and the surface roughnesses of the modified rollers were decreased with increasing wear of modified layers. The small friction coefficient and the small roughness contribute to the improvement of the scuffing capacity, and moreover they might reduce the surface contact stresses and the rolling contact fatigue strength might be improved.

DOI： 10.1299/kikaic.64.1801

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A wear resisting steel was developed in the expectation that it may supersede high phosphorus gray cast iron for improving the strength of sliding elements of a marine diesel engine. In order to investigate the influence of the surface hardness and the surface modification treatment on the scuffing capacity of the wear resisting steel, the two cylinder test was carried out under oil lubrication. The test rollers had two kinds of hardnesses; one was 860 HV for bearings, and the other was 370 HV for sliding materials of cylinders. The electroless Ni-P alloy plating and sulfurizing treatments were employed. The scuffing capacity of the wear resisting steel was larger than that of the high chromium bearing steel SUJ 2. The scuffing capacity of the harder wear resisting steel was smaller than that of the softer one. The electroless Ni-P plating treatment slightly increased the scuffing capacity, while the sulfurizing treatment had no effect on the scuffing capacity of the wear resisting steel.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Journal sliding bearing tests were performed under non-lubricated and water-lubricated conditions. Journals made of Al_2O_3 were slid against bushes made of Sialon, ZrO_2, Al_2O_3, and SUS304 stainless steel. The Al_2O_3/Al_2O_3 combination exhibited the best performance under these test conditions. The wear amount and friction coefficient under the water-lubricated condition were smaller than those under the non-lubricated condition except for the case of Sialon/Al_2O_3 combination. The wear of Sialon might be increased under the influence of the hydrate formed on the sliding surface by tribochemical reaction. The wear amount of Al_2O_3 journal was largest in the case of SUS304/Al_2O_3 combination, in which the wear mode was micro-chipping. On application of Al_2O_3 under the water-lubricated condition, wear of Sialon in the case of Al_2O_3/Sialon combination, stress corrosion wear of ZrO_2 in the case of Al_2O_3/ZrO_2 combination, and wear of Al_2O_3 by micro-chipping in the case of Al_2O_3/SUS304 combination must be considered.

DOI： 10.1299/kikaic.63.3600

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Language：Japanese   Publisher：JAPAN SOC TRIBOLOGISTS  

Web of Science

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Thrust bearing tests were carried out under water lubrication with hot-pressed Sialon, ZrO_2 and Al_2O_3 fine ceramics. The life of Sialon balls mating with Sialon races was the highest, and it was reduced when mating with ZrO_2 or Al_2O_3 races. The lives of ZrO_2 balls and Al_2O_3 balls mating with Sialon races were longer than those of their self-mated contact. Th friction coefficient of thrust bearings consisting of Sialon balls and/or races was comparatively small. The amount of wear of balls or races mating with Sialon was small, while that of Sialon mating with ZrO_2 or Al_2O_3 was large. The main failure modes of Sialon balls were flaking in the case mating with Sialon races, and wear in the cases mating with ZrO_2 and Al_2O_3 races. Those of ZrO_2 and Al_2O_3 balls were wear with micro flaking, and wear, respectively.

DOI： 10.1299/kikaic.62.2798

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The rolling contact fatigue life, reliability and failure mode of Sialon balls were examined through the rolling contact fatigue tests of the hybrid thrust bearing consisting of hot-pressed Sialon balls and bearing steel SUJ2 races. The rolling contact fatigue life of the Sialon balls was complied with the three-parameter Weibull distribution. In case of the smallest balls, the surface of which exhibits micro flaking with increasing the number of cycles, the shape parameter was relatively small and the fatigue life was comparatively dispersed. The rolling contact fatigue life might be influenced by the defects at the surface layer. The average value of the maximum flaking depths lay between the depth of the maximum value of the orthogonal shear stress τ_<yz> and the depth of maximum value of the maximum shear stress τ_<45°>.

DOI： 10.1299/kikaic.61.192

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Language：Japanese   Publisher：JAPAN SOC TRIBOLOGISTS  

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Language：Japanese   Publisher：JAPAN SOC TRIBOLOGISTS  

Web of Science

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Language：Japanese   Publisher：JAPAN SOC TRIBOLOGISTS  

Web of Science

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The friction coefficient of gear tooth flanks is an important factor in clarifying the mechanism of surface failures such as pitting and scoring and in improving the performance of power transmission gears. This is a basic study to establish a method for evaluating the friction coefficient of a spur gear pair under uniformly distributed load along the tooth trace using the fillet strains measured by strain gauges. Experiments with a rack model were carried out with static loads. The frictional and normal forces acting on the working flank were derived by solving the system of equations concerning the fillet strains on the working and nonworking flank sides. The accuracy of the ratio of the friction force to the normal force was examined. The results demonstrate that in order to obtain a meaningful friction coefficient of spur gears it is very important to consider the independence of the relation between the fillet strain and the forces on the working flank.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Thermally refined steel rollers were fatigue-tested under varying specific sliding conditions using a newly developed specific sliding varying-type contact roller testing machine to which an eccentric gear mechanism was applied. The test results were discussed in relation to factors such as specific sliding and frictional torque changes. The surface durability of the roller under a varying specific sliding condition was lower than that under a constant specific sliding condition. The surface durability under a condition where specific sliding was negative on a non-uniform velocity roller was lower than that under a condition of negative specific sliding on a uniform velocity roller. The pitting easily occurred in the negative specific sliding region under high tangential force and at the deceleration process of the rotating roller.

DOI： 10.1299/kikaic.57.1363

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The influence of tip relief on the approach side on the working flank bulk temperature, which has an intimate relationship with scoring occurrence, was studied taking the change of dynamic load into account. The amount of tip interference may be estimated well by Weber and Banaschek's formula for tooth deflection. The working flank bulk temperature is affected more by the change of dynamic load due to the tip relief than by the tip interference. The amount of the tip relief on the approach side and the range of the tip relief should be determined taking the influence of the dynamic load on the working flank bulk temperature into consideration.

DOI： 10.1299/kikaic.56.1564

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The influence of dynamic load on storing capacity was studied using gears having tooth profile errors on the recess sides. Scoring capacity in spur gears is more affected by specific sliding than by dynamic load and increases as specific sliding is decreased. In the mixed lubrication state, the scoring bulk temperature of the working tooth flank is barely influenced by dynamic load when the tip interference on the approach side is negligible, and it may be well estimated by the bulk temperature on the outer surface of the cylinder immediately before seizure in two-cylinder tests. In the calculation of the bulk temperature of the working tooth flank, it is essential to take account of dynamic load and tip interference as well as the heat transfer coefficient and friction coefficient.

DOI： 10.1299/kikaic.56.750