Current Issue : July - September Volume : 2017 Issue Number : 3 Articles : 6 Articles
The effect of two nanoparticle oxides on friction and wear was studied under laboratory test conditions using a reciprocating test\nmachine and two test configurations. The addition of these nanoparticles in base stock oil under certain conditions reduced the\ncoefficient of friction and improved wear, but that depended on the test configuration. Examination of the rubbed surfaces showed\nthe pronounced formation of a tribofilm in some cases, while polishing on the surface was also observed in other cases. Contact\nconfiguration is important when oxide nanoparticles are being evaluated and the conclusions about their efficacy can be vastly\ndifferent....
This article investigates the friction and wear of cold rolled high strength steel at various\ndisplacement amplitudes. Reciprocal sliding tests are carried out using a ball-on-flat testing apparatus.\nThe tangential force occurring at the contact surface between a high strength steel specimen and an\nAISI52100 ball is measured during the tests. After each test, the worn surface profile on the steel\nspecimen is determined. Experimental results show that the ratio of the maximum tangential to\nthe normal force remains at 0.7 after an initial rapid increase, and the ratio does not greatly change\naccording to the imposed displacement amplitudes (in the range of 0.05 mm and 0.3 mm). The wear\nvolume loss on the steel specimen increases according to the number of cycles. It is determined that\nthe wear rate of the specimen changes with respect to the imposed displacement amplitude. That is,\nthe wear rate rapidly increases within the displacement amplitude range of 0.05 mm to 0.09 mm,\nwhile the wear rate gradually increases when the displacement amplitude is greater than 0.2 mm.\nThe obtained results provide the friction and wear behaviors of cold rolled high strength steel in\nfretting and reciprocal sliding regimes....
The aim of this work was to investigate the sliding wear coefficient k, using an\nexperimental sliding wear study on the valve-seat insert contact. Commercial\ninlet valve and seat inserts were used as test specimens. The tests were performed\nat room temperature and at 200Ã?Å¡C, using test duration of 72,000 cycles\nand 18,000 cycles, respectively, and both in dry sliding conditions. A load of 5\nN, an average speed of 22 mm/s and sliding distance of 2.2 mm were used for\nall tests. The sliding wear coefficients were calculated using experimental and\nanalytical methods. The wear volume was higher in the tests at 200Ã?Å¡C both in\nvalve and seat insert specimens. The principal wear mechanisms observed in\nvalve specimen were oxidation and abrasion....
This study examines the role of Graphene nanoplatelets (GNPs) as a solid lubricant\nadditive to aluminum. Pure Al and Al-2 vol % GNP pellets are sintered by Spark Plasma Sintering\n(SPS). Their tribological properties are evaluated by a ball-on-disk tribometer at room temperature\n(RT) and high temperature (200 ââ??¦C). Al-2 vol % GNP composite displayed poor densification\n(91%) and low hardness, resulting in poor wear resistance as compared to pure Al. However\nGNP addition resulted in a lower coefficient of friction (COF) as compared to pure aluminum at\nboth temperatures. The results demonstrated that GNPs contribute to reducing COF by forming\na protective tribolayer. GNPs also play a unique role in reducing oxygen ingress at 200 ââ??¦C. It is\nconcluded that the packing density of a starting powder blend of Al-GNP needs to be improved by\nusing irregular shaped aluminum powder mixed with both larger and smaller GNPs. This would\nresult in greater densification and improve wear rate while maintaining low COF....
The object of this research is to investigate the tribological properties of glycerol lubricant\nwith aluminum nanoparticles as an additive and sodium dodecyl sulfate (SDS) as the dispersive\nmedium for iron to iron friction using a thrust collar tribotester. Meanwhile, the effects of different\nconcentrations of aluminum nanoparticles, SDS, and deionized water in glycerol on tribology\nproperties of iron to iron friction were studied. The experimental parameters were set up according\nto the Taguchi technique, their influence on the coefficient of friction (COF) and wear rate were\nexamined by response surface methodology (RSM) and analysis of variance (ANOVA) methods.\nThe analysis results were employed to optimize the parameters to obtain the best lubricant effects.\nThe optimal combination of the parameters for both minimum COF and wear rate was found to be\n0.6667 weight percent (wt %) of aluminum nanoparticles, 2 wt % of SDS, and 10 wt % of deionized\nwater content of glycerol. The wear surface topography and the average roughness of the surface\nwere also examined using a scanning electron microscope (SEM) and a Mitutoyo Surftest SJ-400\ninstrument. The results show that aluminum nanoparticles used as an additive in lubricant reduce the\nsurface roughness of a collar remarkably. The energy dispersive spectrometer (EDS) was utilized to\nconfirm the deposition of aluminum nanoparticles on the collar surface leading to decreased friction\nand wear....
A three-dimensional (3D) scratch model is proposed to investigate the effects of yield strength of\nboth coatings and substrates. With the help of combined Coulomb and plastic friction, the obtained results\ncomprehensively interpret the experimental phenomena in most metals that with the growth of hardness after\nheat treatment the scratch friction coefficient (SFC) increases. This interpretation could not be done before.\nScratch tests on the surface with or without the coating are discussed. Without the coating the SFC increases\ndue to the decrease of the area with plastic slippage and/or the increase of friction stress during the increase of\nthe yield strength in the material. With a softer substrate the friction stress decreases but the SFC increases,\nwhich is caused by the growth of the entire contact area and surface deformation. Conversely, with a stronger\nsubstrate the SFC decreases due to an intensified plastic slippage. The obtained results pave a new way to\nunderstanding the effects of yield strength on scratch tests, interpret experimental phenomena, and should be\nhelpful for an optimum design in experiments....
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