The Use of Innovative Contact Strip for Pantographs of Electric Rolling Stock. Experience in Operational and Bench Tests

Modern high-tech composite materials are widely used in various sectors of the economy, in particular, in railway transport. Among the areas of application of such innovative materials, the manufacturing of contact strips for pantographs of electric rolling stock should be mentioned. Innovation is primarily understood as the self-lubricating property of the working surface of the linings. The linings made of such materials differ from the traditional graphite (coal) ones by the increased content of metal additives, in particular copper, which limits the possibility of their use on electric rolling stock in the countries of the European Union. Regulatory restrictions on the content of copper (35% and 40%) are associated with possible damage to the contact wire, in the case of using overlays with a content of copper (metals) greater than these restrictions. On the railways of Ukraine (countries of the former USSR), there are also restrictions on the use of linings of different types according to the degree of wear of the contact wire, no more than 40 microns is allowed per 10 thousand passes of the locomotive pantograph along the contact wire. These standards are verified during operational and bench tests. The aim of the article is to present the types of tests and compare the obtained values with similar indicators in the case of using a traditional contact strip for pantographs of electric rolling stock. The results obtained confirm the possibility of using innovative linings on iron networks, since the wear of the contact wire during testing is much lower than that of the normative and knife than for traditional types of linings. In addition, during a set of tests, the fact of improving the quality of the working surface of the contact wire was established, which positively affects the extension of the service life of the contact wire.

Effects of impregnating PTFE filled with added graphite on wear behavior of sintered bronze plain bearings

In this study, self-lubricating porous bronze plain bearing samples were manufactured differently from conventional plain bearings and the wear behaviours were investigated. Plain bearing samples were manufactured by sintering of pre-alloyed spherical CuSn11 bronze powders with grain size of 100– 200 μm. Then, special polymeric composite mixtures were prepared as PTFE (polytetrafluoroethylene) and graphite (GR) additive PTFE mixtures. The GR additive PTFE mixtures were prepared by addition of the GR powder with an average particle size of 200 μm at ratios of 10 wt.% and 20 wt.% into the PTFE solution. Next, the polymeric composite mixtures were impregnated into the porous structure of samples by the spray pulverization coating method. The purpose of the impregnation process was to minimise wear at a longer sliding distance by the gain of self-lubricating property to the samples. The plain bearing samples were produced as three different types (PTFE, PTFE + 10% GR and PTFE + 20% GR). Wear tests were carried out using a plain bearing test rig at different sliding speeds (0.5, 1.0 and 1.5 m s–1) and under applied loads (30, 50 and 70 N). Wear values were determined as weight loss of the samples. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used for the wear analysis of the samples. The results show that the mixtures of PTFE with GR significantly reduced the wear loses of plain bearing surfaces under dry sliding conditions. The PTFE + 10% GR sample had the lowest wear loss under 0.5 m s–1 sliding speed and 30 N applied load conditions after 2.5 hour in comparison with other samples. In other words, the PTFE + 10% GR sample showed lower wear than (31.25%) PTFE sample (without GR additive) and (2.65%) PTFE + 20% GR sample. Also, the wear loss of the PTFE + 20% GR sample (3.67 mg) was slightly increased (difference 1.27 mg/53%) compared to the PTFE + 10% GR sample (2.40 mg) under average load and sliding speed conditions.

Friction and Wear Performance of the New Ceramic Anti-Wear Agent Containing N-B-Mo under Various Loads

The friction and wear experiment employed M-2000 friction and wear tester which friction pair made up of Q235//GCr15 steel, and lubricating oil which contains 3% new N-B-Mo ceramic anti-wear agent was adopted as the medium. The effect of content of new ceramic anti-wear agent on friction and wear property was investigated by using X-Ray diffraction (XRD), optical microscope (OM), et al, and the mechanism of ceramic anti-wear agent was also analyzed. The results showed that in the range of 50-300N load, the friction coefficient is basically related to the size of the load, and the greater the load, the greater the coefficient of friction, the size of the wear rate is not simply increased as the load increases. The wear rate was lowest when the load was 200N. Under this load, the new N-B-Mo ceramic anti-wear agent was generated BN phase which has self-lubricating property at worn surface, reduce the friction coefficient of Q235//GCr15 friction pair and the wear rate of Q235 steel, plays an anti-friction and anti-wear role.

The Bio-Tribological Effect of Poly-Gamma-Glutamic Acid in the Lysozyme-Ionic Contact Lens System

Feeling comfortable is an important issue for contact lens wearers as contact lenses are worn for an extensive period of time. It has been shown that the in vitro friction coefficient of contact lenses is correlated to the degree of in vivo comfort, thus many studies focus on establishing friction testing methods for investigating the friction coefficient of contact lenses or contact lens care solution. We have previously demonstrated the lubricating property of poly-gamma-glutamic acid (γ-PGA)-containing care solution, and it could reduce the high friction coefficient caused by lysozyme. However, the mechanism of how γ-PGA-containing care solution reduces the lysozyme-induced friction coefficient of contact lenses is unclear. We investigated the bio-tribological effect of γ-PGA on ionic contact lenses in the presence of lysozyme by testing load and velocity variations. The ability to remove lysozyme deposition by γ-PGA and viscosity analysis of γ-PGA-containing care solutions were also investigated to understand the potential mechanism. Our results showed that the friction coefficient of γ-PGA-containing care solution with lysozyme was the lowest in both load and velocity variations, and γ-PGA functions distinctly in the lysozyme-ionic contact lens system. We proposed a model of how γ-PGA could reduce the friction coefficient in these two conditions.

Experimental Study of Lubricating Property at Grinding Wheel/Workpiece Interface Under NMQL Grinding

Nanofluid is the suspension formed by lubricating oil and nanoparticles with particles sizes of 1~100 nm, and common nanoparticles include metal nanoparticles (Cu, Ag, etc.), oxide nanoparticles (Al2O3, SiO2, ZrO2, etc.), carbides (CNT, diamond), and MoS2 nanoparticles, etc. Different nanoparticles exhibit various physicochemical properties (e.g., structure and shape), which can influence their tribological characteristics. In this work, six nanofluids, namely, MoS2, SiO2, diamond, carbon nanotubes (CNTs), Al2O3, and ZrO2, were used as minimum quantity lubrication grinding fluids to select the kind of nanoparticles with optimum lubrication performance in grinding nickel alloy GH4169. Experimental results concluded the following: 1) Nanoparticles with spherical or sphere-like molecular structure and nanofluids with high viscosity demonstrate superior lubrication performances. 2) The polishing effect of nanodiamond particles enhances their surface morphology. 3) The lubricating property of the six nanofluids is described in the following order: ZrO2 < CNTs < ND < MoS2 < SiO2 < Al2O3.

Elucidation on the Microstructural and Mechanical Properties of Tailored VAL12 Hybrid Composites with ZrO2 Dispersoids Fabricated by Squeeze Casting Technique

The effect of ZrO2(2, 4, 6 and 8 wt%) dispersoids with 1 wt% graphite on the microstructural, mechanical properties on squeeze cast VAL12 matrix hybrid composite is investigated in the present study. The hybrid composites were characterized using advanced characterization techniques to reveal its microstructural and physical properties. The microscopic examinations using optical and SEM technique reveal that the addition of dispersoids accelerates the nucleation kinetics, thus attaining fine, equiaxial grains in hybrid composites. The squeeze cast composites show almost nil porosity, defects and owing to it, the actual density of the composites are found to be more than 95% as that of the theoretical density values. The hardness values and tensile values increase with respect to the increase in percentage addition of ZrO2. The tensile results show that there is an appreciable increase in the UTS values of composites without much loss in its ductility as the addition of graphite improves the self-lubricating property and provides wettability during the casting. Fractographic studies on tensile tested specimen reveal that the crack occurs in both matrix and particles showing the good interface between matrix and dispersoids. Machinability studies reveal the formation of continuous chips in hybrid composites with a lower percentage of reinforcement (up to 4% ZrO2+ 1%Gr) and segmented chips in case of the composite with 8% ZrO2+ 1%Gr, as the increase in the percentage of dispersoids improve the chip breakability of the composites. On an overall, the hybrid aluminium matrix composites with 1%Gr and 6 % ZrO2unveiled better optimal results.

Poly-Gamma-Glutamic Acid Functions as an Eective Lubricant with Antimicrobial Activity in Multipurpose Contact Lens Care Solutions

In order to perform the multiple functions of disinfection, cleansing, and storage, preservatives are often added to contact lens care solutions. The disadvantage of adding preservatives is that this often causes various eye conditions. However, lens care solutions would not be able to disinfect in the absence of such preservatives. In addition, comfort is an important issue for contact lens wearers due to the long periods of time they are worn. It has been shown that lower friction coefficients are correlated with increased comfort. We have previously developed a multipurpose contact lens care solution in which poly-gamma-glutamic acid (γ-PGA) was the main ingredient. In this study, we investigated the antimicrobial activity and lubricating property of our care solution. We showed that there was a synergetic effect of γ-PGA and chlorine dioxide on antimicrobial activity. We also demonstrated that γ-PGA functioned as a lubricating agent. Our results provided evidence of γ-PGA acting as a multi-functional polymer that could be applied in contact lens care solutions.

Tribological behavior of WS2/oil-impregnated porous polyimide solid/liquid composite system

Purpose This paper aims to study the tribological behavior of the WS2/oil-impregnated porous polyimide (PPI) solid/liquid composite system, in which both PFPE (perfluoropolyether) and SiCH (silahydrocarbons) oils with different hydrocarbon chains were used, respectively. Lubricating mechanism of the composite system was also explored. Design/methodology/approach The tribological behaviors of the WS2 films against the PPI cylindrical pins before and after immersing oil were evaluated under different loads by a reciprocating-type ball-on-disc tribometer. Findings The composite system exhibited the low and stable friction coefficient after the running-in stage, and the lubricant oil played a positive effect. It was found that the WS2/PFPE composite system exhibited more excellent lubricating property, although sole SiCH far exceeds PFPE in lubrication. The abnormal phenomenon mainly resulted from the influence of the oil amount. XRD results on the wear track surfaces indicated that PFPE and SiCH oils with different hydrocarbon chains were likely to preferentially adsorb to the edge plane and basal plane of the WS2 crystals, respectively. Originality/value In previous studies, liquid lubricants were directly dripped or spin-coated on the solid lubricant surface. Based on its potential advantage in application, the tribological behavior and mechanism of the solid lubricating film/oil-impregnated PPI composite system were investigated in this study.