Roughness effect on friction and wear of lubricated plain bearings
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Fuel and emission reductions are one of the high priorities for today’s automotive industries. One option to decrease the fuel consumption is to decrease the frictional losses by using oils and lubricants with lower viscosities in combination with improved surfaces. By decreasing the lubricant viscosity the risk of wear is increased due to a decrease in lubricant film thickness hence the influence of surface roughness becomes more significant. This work investigated the friction and wear behavior of traditionally ground surfaces at various roughness’s as well as an electropolished surface with respect to two lubricants. One standard lubricant, 10W-40 used as a reference and a low viscosity lubricant, 10W-30. Additionally, the influence of process time and current density on the final surface was briefly investigated within the electropolishing method called 3CD. Here only four process times and two current densities were evaluated; 30, 60, 90 and 120 seconds and currents of 15 and 46 Ampere combined with different distances from the substrate. The tribometer with Block-on-Ring configuration used for friction evaluations available at Luleå University of technology was also evaluated as a final step. For the experimental procedure a load of 4 N was selected where the speed was stepwise decreased from 490 rpm down to 10 rpm in order to minimize wear at the beginning of the test. Results shows that the 3CD-process makes the final surface rougher with an appearance similar to etched martensite for the process parameters used. With the process times investigated, times longer than 30 seconds do not alter the surface roughness and shorter times could be essential in achieving a final surface roughness closer to the initial one. Friction test conducted shows interesting results for the 3CD-surface which provides for a low coefficient of friction at high speeds and significantly larger at low speeds. Probably due to dimples in the surface providing with lubricant pockets for better lubrication at high speeds and the large asperity-tips causing an increased friction and wear at low speeds. However, due to alignment problems within the test equipment used no conclusion on what surface roughness to use for engine parts in the future could be made. Only indications on both the 3CD-surface and traditionally ground surface with a roughness of Ra about 0,03 is shown to be of interest. Therefore measure needs to be taken in order to properly use the Block-on-ring configuration for further evaluations.
Place, publisher, year, edition, pages
2013. , 80 p.
IdentifiersURN: urn:nbn:se:ltu:diva-44846Local ID: 2996b1c9-6c94-4a12-b860-f006f427795dOAI: oai:DiVA.org:ltu-44846DiVA: diva2:1018125
Subject / course
Student thesis, at least 30 credits
Materials Engineering, master's level
Validerat; 20130905 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved