In order to investigate the effects of the elastic deformation of the vane-slot on the lubrication characteristics of the vane sliding surface in a rotary compressor, a mixed lubrication analysis considering the elastic deformation has been performed for the vane sliding surface. In this analysis, the modified Reynolds equation and the elastic contact equation, within which the influence of surface roughness is considered, are solved as a coupled problem. The elastic deformation of the vane-slot is calculated by using an FEM model with two-dimensional isoperimetric elements. By comparing the analysis results with that of a rigid-body model, the effects of the elastic deformation of the vane-slot on the lubrication characteristics were clarified. As a result, it is found that the elastic deformation of vane-slot contributes to the smooth reciprocating motion of the vane.

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To analyze the mechanisms of tribochemical reactions occurring between atmospheric gases and materials induced by friction, the authors have developed a friction test system with integrated XPS. The system can analyze worn surfaces in various environments using XPS without air exposure. The results of friction tests in vacuum showed that the native oxide film that formed on the bare surface was worn by friction in vacuum. The results of the friction tests in an Ar gas atmosphere also showed the same results as the friction tests in vacuum. However, it has been suggested that some tribochemical reactions with trace amounts of residual gas occur during friction tests in an Ar gas atmosphere. The results of the friction tests and XPS analyses indicated that our friction test system with integrated XPS was useful for analyzing tribochemical reactions between atmospheric gases and materials.

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Fretting wear tests of some steel materials under gross slip condition were conducted in hydrogen gas to obtain basic knowledge on its tribological effect. The tests were done also in nitrogen, argon, and air for comparison. The amount of wear was largest in air among these gases, and the highest insulation voltage between specimens was recorded also in air. In the gas-filled atmosphere in a hermetically-sealed vessel, where some impurities are left, wear is smaller in hydrogen than in air, but larger than in nitrogen and argon. This corresponds to the difference in insulation voltage, higher in hydrogen than in nitrogen and argon. When the gases were supplied continuously in the vicinity of the contact point at high flow rate to decrease the influence of impurities, the insulation voltage and wear decreased considerably with the supplying rate. As for a comparison on wear of the steel materials with the continuous gas supplying, the difference in wear can be attributed to specimen hardness. Furthermore, exposure of specimens to high pressure hydrogen (40 MPa, 373 K, several tens to 250 hour) prior to the fretting tests, which is a simple simulation of practical use in high pressure hydrogen, increased wear in most steels tested.

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In this paper the nonlinear dry reciprocating wear behavior of three composites A319/15%SiCp A336/15%SiCp and A390/15%SiCp subjected to high temperature were reported. Composites were produced through liquid metal metallurgy route. Five controllable input parameters selected for the wear study were applied load, reciprocating velocity, sliding distance, counter surface temperature and silicon content in composites. Two output responses wear and coefficient of friction were measured. The input parameter levels were fixed through pilot experiment conducted in the indigenously developed reciprocating friction and wear test rig. The counter surface material used for the wear study was cast iron having Vickers hardness of 244 HVN. Wear study under dry condition was carried out through response surface methodology by considering five input parameters as variables and two output parameters as responses. It had been demonstrated through established equations that the nonlinearity is more pronounced with the increase in applied load and reciprocating velocity. Also it was found that high percentage silicon content composite exhibited a low wear compared to the low percentage silicon content composite. Moreover, the wear increased with increasing applied load, sliding distance and counter surface temperature and it decreased with silicon content in composites and square of reciprocating velocity.

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Alumina has been widely used in joint prostheses due to its excellent biocompatibility, wear and corrosion resistance, low friction, high mechanical strength and low cost. However, the further improvement in fracture toughness and wear resistance is required for severe activities. In this work Y-TZP (100 nm), TiO₂ (50 nm), were added to Al₂O₃ powder (300 nm) to prepare new candidate composite materials for prostheses. These starting powders were mixed and hot pressed. Mechanical properties as Vickers hardness and fracture toughness were estimated using the indentation method. Wear tests were carried out in a ball-on-plate tribometer, with a frequency of 1 Hz, a load of 49 N, for 4h. Alumina and silicon nitride balls were used as counterfaces. Distilled water and Fetal Bovine Serum Solution were used as environment. Lowest specific wear rate was about 10^-8 mm³/Nm and lowest coefficient of friction was around 0.2 for the case of silicon nitride ball. Furthermore the chemical species formed on the surface were studied.

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Friction and wear properties of the copper/carbon/RB ceramics (Cu/C/RBC) composite were investigated under electrical current with and without arc-discharge. The weight fraction and the mean diameter of RB ceramics powder were 5 wt% and 4.9 μm, respectively, in the Cu/C/RBC composite. Friction tests were conducted with the block-on-ring friction apparatus. The Cu/C/RBC and the copper/carbon (Cu/C) composite, the conventional pantograph slider material of a railway current collector, were used as block specimens. Under electrical current without arc-discharge, the Cu/C/RBC composite showed 98% reduction in the specific wear rate of the block specimen, 23% reduction in that of the ring specimen, and 75% reduction in the friction coefficient over the conventional Cu/C composite. Under electrical current with arc-discharge, the Cu/C/RBC composite showed the wear resistance to arc-discharge equivalent to the conventional Cu/C composite.

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The effect of molybdenum trioxide (MoO₃) on the friction and wear of aluminum bronze was studied at the temperature up to 973 K. MoO₃ powder supplied to the sliding interface between aluminum bronze and stainless steel reduced friction coefficient and wear of materials at the temperature from 773 to 973 K. Copper-molybdenum oxide was generated by sliding aluminum bronze and stainless steel in presence of MoO₃ powder at high temperature. This oxide is supposed to be Cu₃Mo₂O₉ from the results of XRD analysis of the friction track. The authors obtained Cu₃Mo₂O₉ powder by heating the mixture of MoO₃ powder and CuO powder in air. The lubricity of Cu₃Mo₂O₉ powder was compared with that of MoO₃ powder at the temperature up to 973 K. Cu₃Mo₂O₉ powder reduced wear and friction at the temperature from 773 to 973 K while MoO₃ powder could not work as lubricant at the temperature over 873 K.

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