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Tribological Behavior (tribological + behavior)
Selected AbstractsTribological Behavior of SiC-Reinforced Ti3SiC2 -Based Composites under Dry Condition and under Lubricated Condition with Water and EthanolJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006Yuko Hibi To evaluate the lubrication compatibility of SiC-reinforced Ti3SiC2 -based composites, i.e., a Ti3SiC2/SiC composite, with water and alcohol, sliding experiments were conducted under dry condition and lubricated with water and C2H5OH. The friction and wear of the Ti3SiC2/SiC composite decreased in the order of dry condition, in water, and in C2H5OH. The worn surfaces indicated that oxide masses, which caused oxidation wear and abrasive wear, were formed by tribo-oxidation on the sliding surface under the dry condition and in water, while tribo-oxidation scarcely occurred in C2H5OH. [source] Characterizations of Magnetron Sputtered CrSiN/ZrN Multilayer Coatings,from Structure to Tribological Behaviors,ADVANCED ENGINEERING MATERIALS, Issue 8 2009Zhiguo Zhang In this study, CrSiN/ZrN multilayer coatings were prepared by a reactive magnetron sputtering system. The evolution of their microstructure, mechanical, and tribological properties as a function of the multilayer modulation period was studied. The results showed that the multilayers had a good modulation structure. CrSiN and ZrN individual layer in the multilayers were "amorphous-like" and amorphous structure, respectively. [source] Tribological behavior of pure and graphite-filled polyimides under atmospheric conditionsPOLYMER ENGINEERING & SCIENCE, Issue 8 2003P. Samyn As the use of common engineering plastics in tribological systems is limited to low sliding velocities and low loads because of creep and insufficient temperature resistance, there is increasing interest in application of high-performance polymers such as polyimides, characterized by their ability to maintain favorable mechanical properties up to their melting point. However, for practical design, tribotesting remains necessary for determination of the material's performance under a given contact situation. In this article, two commercially available polyimides are tested at relatively high sliding velocities and contact pressures under atmospheric conditions of temperature and humidity. A consistent overview of tendencies in friction and wear for pure polyimides as a function of applied normal loads and sliding velocities is given. Addition of 15% by weight graphite powder as internal solid lubricant strongly influences friction and wear. Its behavior is compared with pure polyimide grades and differences are discussed in relation with experimental measured bulk-temperatures. A linear temperature law is derived as a function of pv-levels and a steady-state condition is found at different temperature levels, in accordance with thermal conductivity of the polymer bulks. In case of graphite additives, a steady state in temperature coincides with the regime condition of wear rate. [source] Tribological behaviors of aligned carbon nanotube/fullerene-epoxy nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2008Huan Wang The tribological properties of aligned CNT/fullerene-epoxy nanocomposites were studied by nanoscratch, nanowear, and nano-indentation tests. Compared with neat epoxy, aligned CNT/fullerene-epoxy nanocomposites showed lower friction coefficient in scratch tests, a reduction of 38.1 and 26.2%, respectively. In addition, the aligned CNT-epoxy composite showed better wear resistance and its hardness and Young's modulus increased by 29.4 and 16.8%, respectively. In contrast, for a fullerene-epoxy nanocomposite with 10 wt% fullerenes, the hardness decreased by 50% and the Young's modulus decreased by more than 60% when compared with the neat epoxy. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Influence of solid lubricant reinforcement on wear behavior of Kevlar fabric compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Fang Guo Abstract The friction and wear behavior of Kevlar fabric composites reinforced by PTFE or graphite powders was investigated using a Xuanwu-III friction and wear tester at dry sliding condition, with the unfilled Kevlar fabric composite as a reference. The worn surfaces were analyzed by means of scanning electron microscope, and X-ray photoelectron spectroscopy. It was found that PTFE or graphite as fillers could significantly improve the tribological behavior of the Kevlar fabric composites, and the Kevlar fabric composites filled with 20% PTFE exhibited the best antiwear and antifriction ability among all evaluated cases. The transfer films established with two lubricants in sliding wear of composites against metallic counterparts made contributions to reducing friction coefficient and wear rate of Kevlar fabric composites. In particular, FeF2 generated in the sliding of Kevlar fabric composites filled with PTFE against counterpart pin improved the bonding strength between the transfer film and counterpart surface, which accounted for the lowest friction coefficient and wear rate of the Kevlar fabric composites filled with PTFE measured in the testing. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008. [source] Effect of different types of peroxides on properties of vulcanized EPDM + PP blendsPOLYMER COMPOSITES, Issue 10 2010Witold Brostow Mechanical and tribological behavior of several dynamic vulcanizate blends of polypropylene (PP) with ethylene-propylene-diene rubber (EPDM) was examined and compared with those of uncrosslinked blends. Vulcanization was performed using two types of organic peroxides combined with (meth)acrylate coagent. The effect of different types and concentrations of peroxides as crosslinking agents on the properties of the resulting materials were investigated. Dicumyl peroxide (DCP) provides higher reactivity and exhibits nearly the same crosslinking efficiency for both 60/40 and 50/50 blends; almost fully crosslinked samples are obtained if the compound contains 1.0 or 2.0 wt% DCP. These results correlate to the gel content and mechanical properties of our materials. Variation of PP + elastomer ratio does not have a significant influence on friction. From 60/40 group of composites, lower friction values were obtained for samples cured with 0.5 wt% benzoyl peroxide (BP) and 1.0 wt% DCP. The tribological properties of the samples with higher amount of DCP show rubbery rather than a toughened thermoplastic behavior. Wear of the composites decreases with the increasing concentration of the curing agent. Compared to BP, the samples cured with DCP display lower wear. POLYM. COMPOS., 31:1678,1691, 2010. © 2010 Society of Plastics Engineers. [source] Increased friction coefficient and superficial zone protein expression in patients with advanced osteoarthritisARTHRITIS & RHEUMATISM, Issue 9 2010C. P. Neu Objective To quantify the concentration of superficial zone protein (SZP) in the articular cartilage and synovial fluid of patients with advanced osteoarthritis (OA) and to further correlate the SZP content with the friction coefficient, OA severity, and levels of proinflammatory cytokines. Methods Samples of articular cartilage and synovial fluid were obtained from patients undergoing elective total knee replacement surgery. Additional normal samples were obtained from donated body program and tissue bank sources. Regional SZP expression in cartilage obtained from the femoral condyles was quantified by enzyme-linked immunosorbent assay (ELISA) and visualized by immunohistochemistry. Friction coefficient measurements of cartilage plugs slid in the boundary lubrication system were obtained. OA severity was graded using histochemical analyses. The concentrations of SZP and proinflammatory cytokines in synovial fluid were determined by ELISA. Results A pattern of SZP localization in knee cartilage was identified, with load-bearing regions exhibiting high SZP expression. SZP expression patterns were correlated with friction coefficient and OA severity; however, SZP expression was observed in all samples at the articular surface, regardless of OA severity. SZP expression and aspirate volume of synovial fluid were higher in OA patients than in normal controls. Expression of cytokines was elevated in the synovial fluid of some patients. Conclusion Our findings indicate a mechanochemical coupling in which physical forces regulate OA severity and joint lubrication. The findings of this study also suggest that SZP may be ineffective in reducing joint friction in the boundary lubrication mode at an advanced stage of OA, where other mechanisms may dominate the observed tribological behavior. [source] Mechanotransduction of bovine articular cartilage superficial zone protein by transforming growth factor , signalingARTHRITIS & RHEUMATISM, Issue 11 2007Corey P. Neu Objective Mechanical signals are key determinants in tissue morphogenesis, maintenance, and restoration strategies in regenerative medicine, although molecular mechanisms of mechanotransduction remain to be elucidated. This study was undertaken to investigate the mechanotransduction process of expression of superficial zone protein (SZP), a critical joint lubricant. Methods Regional expression of SZP was first quantified in cartilage obtained from the femoral condyles of immature bovines, using immunoblotting, and visualized by immunohistochemistry. Contact pressure mapping in whole joints was accomplished using pressure-sensitive film and a load application system for joint testing. Friction measurements on cartilage plugs were acquired under boundary lubrication conditions using a pin-on-disk tribometer modified for reciprocating sliding. Direct mechanical stimulation by shear loading of articular cartilage explants was performed with and without inhibition of transforming growth factor , (TGF,) signaling, and SZP content in media was quantified by enzyme-linked immunosorbent assay. Results An unexpected pattern of SZP localization in knee cartilage was initially identified, with anterior regions exhibiting high levels of SZP expression. Regional SZP patterns were regulated by mechanical signals and correlated with tribological behavior. Direct relationships were demonstrated between high levels of SZP expression, maximum contact pressures, and low friction coefficients. Levels of SZP expression and accumulation were increased by applying shear stress, depending on location within the knee, and were decreased to control levels with the use of a specific inhibitor of TGF, receptor type I kinase and subsequent phospho-Smad2/3 activity. Conclusion These findings indicate a new role for TGF, signaling in the mechanism of cellular mechanotransduction that is especially significant for joint lubrication. [source] Mechanical and tribological behaviors of PA66/PVDF blends filled with calcium sulphate whiskersPOLYMER COMPOSITES, Issue 9 2009Hong-Gang Wang The mechanical and tribological performance of the PA66/PVDF blends filled with various amount of calcium sulphate whiskers (CSW) was investigated. The whiskers improve the tensile and flexural performance of the PA66/PVDF blends. Meanwhile, the addition of CSW obviously decreases friction coefficient and improves the wear resistance of the blends. With the further increase of CSW, friction coefficient of the blends relatively keeps stable and the wear resistance of the blends slightly decreases. The PA66/PVDF blends filled with 5 wt% CSW exhibited the best anti-wear ability. FTIR analysis shows that the chemical change has not occurred in the debris. XPS analysis shows that some tribo-chemical reactions have occurred during friction process and produces some compounds such as FeF2, Fe2O3 on the transfer film surfaces. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers [source] Effectual dispersion of carbon nanofibers in polyetherimide composites and their mechanical and tribological propertiesPOLYMER ENGINEERING & SCIENCE, Issue 10 2010Bin Li The use of proliferation of nanotechnology in commercial applications is driving requirements for minimal chemical processing and simple processes in industry. Carbon nanofiber (CNF) products possess very high purity levels without the need of purification processing before use and are in growing demand for this quality. Polyetherimide (PEI) has excellent mechanical and thermal performance, but its high viscosity makes its nanocomposites processing very challenging. In this study, a facile melt-mixing method was used to fabricate PEI nanocomposites with as received and physically treated CNFs. The dispersion of CNFs was characterized by scanning electron microscopy, transmitted optical microscopy, and electrometer with large-area electrodes. The results showed that the facile and powerful melt-mixing method is effective in homogeneously dispersing CNFs in the PEI matrix. The flexural and tribological characteristics were investigated and the formation of spatial networks of CNFs and weak interfacial bonding were considered as competitive factors to enhanced flexural properties. The composites with 1.0 wt% CNFs showed flexural strength and toughness increased by more than 50 and 550%, respectively, but showed very high wear rate comparable with that of pure PEI. The length of the CNFs also exerted great influences on both mechanical and tribological behaviors. POLYM. ENG. SCI., 50:1914,1922, 2010. © 2010 Society of Plastics Engineers [source] | ||||||||||