Current Issue : January - March Volume : 2017 Issue Number : 1 Articles : 5 Articles
Airborne particulate emissions originating from the wear of pads and rotors of disc brakes contribute up to 50% of the total road\nemissions in Europe. The wear process that takes place on a mesoscopic length scale in the contact interfaces between the pads\nand rotors can be explained by the creation and destruction of contact plateaus. Due to this complex contact situation, it is hard to\npredict how changes in the wear and material parameters of the pad friction material will affect the friction and wear emissions.\nThis paper reports on an investigation of the effect of different parameters of the pad friction material on the coefficient of friction\nand wear emissions. A full factorial design is developed using a simplified version of a previously developed cellular automaton\napproach to investigate the effect of four factors on the coefficient of friction and wear emission. The simulated result indicates\nthat a stable third body, a high specific wear, and a relatively high amount of metal fibres yield a high and stable mean coefficient\nof friction, while a stable third body, a low specific wear, a stable resin, and a relatively high amount of metal fibres give low wear\nemissions....
This study involves the application of carbon nanotubes (CNTs) to a piston ring and cylinder liner\nsystem in order to investigate their effect on friction and wear under dry and lubricated conditions. Carbon\nnanotubes were used as a solid lubricant and lubricant additive in dry and lubricated conditions, respectively.\nSimulation and measurement of friction and wear were conducted using a reciprocating tribometer. Surface\nanalysis was performed using a scanning electron microscope and an energy dispersive spectrometer. The\nresults indicate that carbon nanotubes can considerably improve the tribological performance of a piston ring\nand cylinder liner system under dry sliding conditions, whereas improvement under lubricated conditions is\nnot obvious. Under dry friction, the effective time of the CNTs is limited and the friction coefficient decreases\nwith an increase in CNT content. Furthermore, the dominant wear mechanism during dry friction is adhesive...
Finely dispersed copper nanoparticles were added as an additive to fully-formulated\nengine oils. The copper additive was in colloidal form, with an inner core of Cu2+ atoms covered\nby surfactants to form stable reverse micelles that are completely dispersible in the base oil.\nThe tribological process to form protective films at the metal surface is comprised of three phases.\nPhase I can be considered a physical process involving the build-up of polar molecules by\nabsorption to produce a friction modifier film, whereas phases II and III have to be treated as\nmechanochemical processes comprising a combination of redox reactions and a third body formation.\nThe tribological performance was investigated using atomic force microscopy, a microtribometer,\na pin-on-disk tribometer in combination with continuous and high-resolution wear measurements\nwith radionuclide technique, and high pressure stressing in a thrust roller bearing test rig. In addition,\nthe nanostructure of the additive was characterized by atomic force microscopy. Finally, the chemical\ncomposition of the metal surface was analyzed using photoelectron spectroscopy....
This study investigates friction and film thickness\nin elastohydrodynamic contacts of machined, rough\nsurfaces, where roughness is dominated by longitudinal\nridges parallel to the rolling/sliding direction. A ball-ondisc\ntribometer was used to simultaneously measure friction\nand film thickness in rough contacts as well as with\nnominally smooth specimens for comparison. The studied\nrough surfaces were selected so that the influence of the\nroot-mean-square roughness and roughness wavelength can\nbe assessed. Friction and film measurements were taken\nover a range of slideââ?¬â??roll ratios and speeds and with two\nlubricating oils with different viscosities, hence covering a\nwide range of specific film thicknesses. The measurements\nwith the nominally smooth specimens show that friction is\nstrongly influenced by thermal effects at high SRRs and\nthat the transition from mixed/boundary to full EHD\nlubrication occurs at lambda ratios greater than three. At\nlow speeds, the rough specimens are found to generate\nhigher friction than the smooth ones for all the roughness\nstructures considered, and this is shown to be related to the\nthinner minimum film thickness. Comparison of friction in\nrough and smooth contacts shows that the total friction in\nrough contacts can be divided into two components: one\nthat is equivalent to friction in smooth contacts under the\nsame conditions and is dependent on the slideââ?¬â??roll ratio,\nand the other that is due to the presence of roughness and is\nindependent of the slideââ?¬â??roll ratio under the conditions\ntested. Further analysis of the minimum film thickness on\ntops of roughness ridges indicates that even after the full\nlift-off, an effect of the roughness on friction persists and is\nmost likely related to the local shear stress in the micro-\nEHD contacts on the top of roughness ridges. At even\nhigher speeds, the difference in friction between the rough\nand smooth specimens vanishes....
Thermally sprayed coatings have been used in various fields of industry for enhancing\nsurface characteristics of materials and extending their service life. The contact\nsurface of some mechanical equipment such as the fine pulverization equipment\nwhich is used in the woody biomass production process is required to have wear resistance\nin the water environment. Thermally sprayed coatings would be a good candidate\nto improve surface wear resistance under water lubrication. The objective of\nthis study was to evaluate the tribological performance of thermally sprayed coatings\nunder water lubrication. Thermally sprayed coatings which were classified into WC,\nWB and Ni spraying of three categories were compared with water-lubricated sliding\ntest at a sliding velocity of 0.02 m/s and mean pressure of p0 = 10 MPa with a ringon-\ndisk apparatus. Thermally sprayed coatings showed comparatively high friction\ncoefficient and well wear resistance under water lubrication. WC contained coatings\nshowed better wear resistance than WB and Ni coatings. Thermally sprayed coatings\nshowed obviously different mechanical properties and tribological behaviors, and the\neffect of wettability and hardness on tribological characteristics was discussed under\nwater lubrication. Friction coefficient increased as the surface contact angle of thermally\nsprayed coatings increased. The wear rate decreased as the surface hardness of\nthermally sprayed coatings increased. Wear resistance of thermally sprayed coatings\nwas excellent under water lubrication. WC contained coatings showed lower wear\nrate than WB and Ni coatings. WC-14CoCr coating showed the lowest wear rate....
Loading....