查看更多>>摘要：Thermoplastic urethane (TPU) is a major material for manufacturing studs for spike shoes. Spike shoes require high wear resistance and injection moldability. The TPU surface experiences impact and shear from soil ground particles. However, it is commonly difficult to estimate actual wear resistance of TPU studs based on table tests of solid particle erosion resistance or sliding wear resistance. In this study, we propose a new table test for estimating the wear resistance of TPU studs based on actual use in soccer activities. A wear resistance measurement method was developed where the TPU surface collided with abrasive paper and the wear volume measured in a table test. The wear volume increased with the storage elastic modulus of TPUs and was sensitive to the impact angle between TPU sheet and abrasive paper. These results were compared with the wear height of TPU studs from a practical use test, and it was confirmed that the wear resistance of TPU studs in a practical use matched to the results in table test when the abrasive paper on the TPU surface was struck at a 10 degrees angle.
查看更多>>摘要：Nanoparticles acting as additives to improve the tribological performance of base fluids have attracted much attention in the last several decades to lower wear loss, reduce the frictional force, enhance the service performance and extend the service life of sliding components. Different nanoparticles with various concentrations, mixing methodologies, surfactants and surface modifications have been frequently studied for in-depth understanding. The present research reviews the applications of nanoparticles as lubricant additives and their tribological properties. The common nano-sized materials, production processes, classifications of surfactants, surface modifications, friction reduction and anti-wear behavior of various nanolubricants are summarized. The potential mechanisms which can result in excellent tribological properties of nanolubricants are discussed. The limitations and challenges in applications and commercialization of nanolubricants are introduced. Finally, the recommendations for the development and the directions of future studies related to nanolubricants are provided. The information reported in the present work can be utilized as references in the development of highperformance nanolubricants and specific applications of nanolubricants in mechanical systems.
查看更多>>摘要：In prosthetic joints, frictional heating may cause protein denaturation in synovial fluid which may affect its lubrication properties. In arthroplasty, conventional ultra-high molecular weight polyethylene (UHMWPE) is being gradually replaced by vitamin E stabilized, extensively cross-linked UHMWPE (VEXLPE) with a superior combination of wear and oxidation resistance. There is scarcity of literature on UHMWPE vs.VEXLPE friction. A noncyclic, single-station friction measurement device, the Friction RandomPOD, was recently introduced. The direction of sliding, velocity, acceleration, and load varied randomly within certain, biomechanically justified limits. The measurement of the coefficient of friction was based on a three-axial load cell. In order to increase the testing capacity, the number of test stations was now increased to 4 using similar load cells. One-week tests were performed with pins made of UHMWPE and VEXLPE against CoCr in calf serum lubrication at 4 degrees C, 20 degrees C and 37 degrees C. The lower temperatures were included to prevent or retard protein denaturation. The lowest friction and wear were observed at 37 degrees C. At this temperature, the mean of the coefficient of friction of VEXLPE was 55% lower than that of UHMWPE. The wear of VEXLPE was always lower than that of UHMWPE.
查看更多>>摘要：Inspired by natural nacre, hierarchically structured graphene oxide (GO) composite coatings reinforced with different concentrations of polyvinyl alcohol (PVA) were fabricated for development of novel protective surface coatings. It was found that the tribological performance of the GO coating deposited on 304 stainless steel could be significantly improved by including PVA in the coating. The GO/PVA composite coating showed a low friction coefficient of 0.085 and a significant reduction in wear rate compared to that of the GO coating. It was determined that incorporation of PVA between the GO layers enhanced the durability of the coatings. These results showed that PVA can be effectively used as a reinforcing agent of hierarchically structured GO coatings for low friction and wear applications.
查看更多>>摘要：Pure Ti has potential applications in the desalination and chemical industries, as well as in the construction of seagoing vessels. In such applications, the degradation of metals via cavitation erosion can be a significant concern. The present work examined the cavitation erosion mechanism of pure Ti using electron back-scatter diffraction, scanning electron microscopy and transmission electron microscopy. Triple junctions and grain boundaries were determined to be the preferential sites for the initiation of cavitation damage such that, after a 4 h exposure to cavitation erosion, 87% of triple junctions and 36% of grain boundaries were eroded. The misorientation angles of the damaged grain boundaries were all greater than 42 degrees. The cavitation damage was determined to have been induced by strain concentration and this damage appeared in the form of extrusions, microcracks and subsequent material removal. The material removal propagated slowly toward grain interiors via the formation of small pieces of spatting. Finally, coarse grains were found to increase resistance to cavitation erosion; other approaches to modifying the microstructure of pure Ti are also discussed herein.
查看更多>>摘要：Greases with two different thickeners, namely lithium complex (LiX) and polypropylene (PP), and three different base oil viscosities were investigated in fretting with varying displacement amplitude and applied normal load. The material combinations silver-coated copper/silver-coated copper (Ag/Cu vs Ag/Cu) and steel/steel were investigated. Fretting maps of four of the six evaluated greases were constructed as a tool to better understand and compare the lubrication mechanisms of the varying grease types. Parameters such as applied normal load, displacement amplitude, material combination, contact area growth, thickener type, base oil viscosity, chemical effects, etc., all influence the grease lubricating properties and the prevailing fretting regime. This study shows the importance of understanding the application and its contact conditions, as well as how different grease types are affected by varying test parameters. Very different lubrication effects are found for the same grease type, depending on test conditions. Surface analysis of the formed wear marks is presented.
查看更多>>摘要：This paper investigates the feasibility of improving the tribological properties of Ti3SiC2 MAX phase composite by employing laser surface texturing (LST). Two different surface textures (line and square) were produced on the bulk sample using a continuous laser. The friction and wear performance of the line and square textured surface was investigated against an untextured surface following reciprocating dry-sliding contact against hardened steel and alumina counterface at ambient conditions. Sliding-induced chemical and topographical changes were studied by 3D optical profilometry, Raman spectroscopy, and scanning electron microscopy. Test results show that both the line and square textured MAX phase composite surface exhibit excellent wear performance as well as a reduction in friction. The improved performance is linked to the combined effect of surface texture, topography, surface hardening and tribofilm evolution. The type of counterface material played a vital role in the nature of tribo-oxidation product formed as well as the extent of wear of the MAX phase material.
NSTL
Elsevier