Proceedings of SerbiaTrib '13

Serbian TribologySocietySERBIATRIB ‘1313 th International Conference onTribologyKragujevac, Serbia, 15 – 17 May 2013Faculty of Engineeringin KragujevacWEAR OF POLISHED STEEL SURFACES IN DRY FRICTIONLINEAR CONTACT ON POLIMER COMPOSITES WITH GLASSFIBRESDorin Rus 1 Lucian Capitanu 21 Mechanical Departament, Institute of Civil Engineering, 59 Plevnei Way, 050141, Bucharest, Romania, e-dorinrus@gmail.com2* Institute of Solid Mechanics of the Romanian Academy, 15 Constantin Mille, 010141, Bucharest, Romanialuciancapitanu@yahoo.comAbstract: It is generally known that the friction and wear between polymers and polished steel surfaces has aspecial character, the behaviour to friction and wear of a certain polymer might not be valid for a differentpolymer, moreover in dry friction conditions. In this paper, we study the reaction to wear of certain polymerswith short glass fibres on different steel surfaces, considering the linear friction contact, observing thefriction influence over the metallic surfaces wear. The paper includes also its analysis over the steel’s wearfrom different points of view: the reinforcement content influence and tribological parameters (load, contactpressure, sliding speed, contact temperature, etc.). Thus, we present our findings related to the fact that theabrasive component of the friction force is more significant than the adhesive component, which generally isspecific to the polymers’ friction. Our detections also state that, in the case of the polyamide with 30% glassfibres, the steel surface linear wear rate order are of 10 -4 mm/h, respectively the order of volumetric wearrate is of 10 -6 cm 3 /h. The resulting volumetric wear coefficients are of the order (10 -11 – 10 -12 ) cm 3 /cm andrespectively linear wear coefficients of 10 -9 mm/cm.Keywords: wear, composite thermoplastics, comparative wearing coefficient.1. INTRODUCTIONThe tribological behaviour of polymers hasdistinctive characteristics, some of them beingdescribed by Bowden and Tabor [1]. The mainconcept related to the polymers’ tribology iscomposed of three basic elements involved infriction: (i) junctions adhesion, their type andresistance; (ii) materials’ shearing and fracturethrough friction during the contact; and (iii) the realcontact area.Friction’s straining component results from thepolymer’s resistance to “ploughing” made by theasperities existing on the harder counter-face. Thepolymer’s surface asperities bear elastic, plastic andviscous-elastic strains, according to the material’sproperties. Friction adhesion component comes outof the adhesion junctions formed on the real contactspots between the paired surfaces. Friction adhesioncomponent in what the polymers are concerned isconsidered to be much greater than the strainingcomponent. Special attention should be granted tothe transfer films, these transfer films being the keyfactors determining the tribological behaviour ofpolymers and polymeric composites. In what theglass fibers reinforced polymer is concerned, wealso encounter a strong abrasive component [2].Several models were developed to describe thecontact adhesion. The Johnson-Kendall-Roberts(JKR) model, mentioned sometimes as the contactmechanics model [3-4] and the Derjaguin-Muller-Toporov (DMT) model [5] are the best known. Themodels’ comparative analysis [6] shows that theJKR model is applied to bodies with micrometricdimensions and larger than that, with polymerproperties, whilst the DMT model is valid forbodies with nanometer dimensions, with metalproperties.Several authors [7-17] studied the polymers’friction on hard surfaces. By using the method of58 13 th International Conference on Tribology – Serbiatrib’13