Tribological researches of composite materials assigned for machinery parts of technical transport means
Andrzej Posmyk
Quarterly No. 1, 2010 pages 70-75
DOI:
keywords: tribological investigations, composite materials, choice of pairing, samples preparing
abstract Basic information to the point of investigations methods of tribological properties of composite materials assigned for sliding pairs of technical transport means using in reciprocated and rotational movement has been described. The choice principles of tribological testers depend on using conditions of real objects with machinery parts made from composite materials have been described. A frictional pairings sample from the piston/cylinder liner-group from combustion engines and their equivalent pairings from tribological testers was given. The principle of choice of material for samples and countersamples, the conditions for machining of surfaces destined for rubbing were discussed. Two kinds of tribological pairings, i.e. sliding pair with reciprocated and sliding pair with rotational movement have been named. The first pairing is represented by piston ring (made of cast iron or cast iron with chromium-ceramic covering) and cylinder liner sleeve (made of composite material). To simulate of using conditions of this pairing can be used tester with “cube on block” couple. Crankshaft and journal bearing represent the second one. The crankshaft can be made of composite material, steel (wrought shafts) and of cast iron (cast shafts). The bearing is produced of composite material, for example from aluminum alloy-matrix with graphite as reinforcing phase. To simulate of using conditions of this pairing can be used tester with “block on ring” couple. Tribological tests can be conducted with lubrication agent, for example combustion engine oil ant under friction in air conditions. During preparation of samples for investigations an attention should be paid to proper choice of materials for samples and countersamples because friction coefficient for example in pairing rubber/steel is about 20% less then steel/rubber. During machining of cast iron graphite is removed from the surface, which results in decreasing of tribological properties. Therefore the surface of samples destined for sliding should be machined in the same way that the machinery parts. The best way for samples preparing is to make them from the original machinery parts, for example from a piston ring. If the sliding surface of piston ring is covered with chromium-ceramic layer samples for tests should be prepared in that way that their sliding layer is the original sliding layer of piston. Duration of tribological test with samples covered with Cr-Al2O3-layer should be adjusts to the covering thickness.