Tribology in Industry

284-290

Authors: N.K. Myshkin, S.S. Pesetskii

Polymer tribology is based on the analysis of abrasion, adhesion, and fatigue of polymer materials in a friction contact. The structural features of polymers provide a variety of tribological applications of basic polymers mostly as matrices and fillers of composite materials. Recently polymer nanocomposites are used for making components of various tribosystems. A short review of polymer materials for tribosystems is presented. The main results of studies in friction and wear of polymers are given. Formation of the real area of contact is evaluated when taking account of polymer viscoelasticity and the effects of temperature and load in the contact. Adhesion of polymers and its part in friction transfer is considered. Various aspects of friction and wear tests of polymer materials for estimation of their characteristics, prediction of service life in different operational conditions are discussed. Practical examples of applications of polymer composites and nanocomposites in various branches of industry are given.

299-308

Authors: G. Pantazopoulos, P. Psyllaki

The present study is focused on elucidating the wear mechanisms taking place during sliding friction of five (5) steel grades subjected to Trufftriding. For this purpose, three sliding friction experimental configurations were used and the friction coefficients, real-time-recorded during testing, were correlated to the post-testing microscopic observations of the worn surfaces. Finally, the experimental findings were evaluated with respect to the initial microstructure of the tool steels in their as-received and/or heat-treated state. In the case of non-conformal point contact against ceramic counterbodies, the friction coefficient was found to depend only on the steel grade and the particular counterbody, tending to a constant value, regardless of the applied load and/or its heat- or surface treatment. In the case of conformal plane contact against hardened steel, each steel grade exhibited an applied pressure range within which the wear coefficient remains practically constant, whereas for higher pressure values, seizure occurred. Nitrocarburising “displaced” the constant wear coefficient range towards higher pressure values, resulting in seizure retardation.

320-329

Authors: A. Vencl, B. Katavić, D. Marković, M. Ristić, B. Gligorijević

During the coal pulverizing, the working parts of the ventilation mill are being worn by the sand particles. For this reason, the working parts are usually protected with materials resistant to wear (hardfaced/thermal sprayed coatings). The aim of this study was to evaluate the tribological performance of four different types of coatings as candidates for wear protection of the mill’s working parts. The coatings were produced by using the filler materials with the following nominal chemical composition: NiFeBSi-WC, NiCrBSiC, FeCrCTiSi, and FeCrNiCSiBMn, and by using the plasma arc welding and flame and electric arc spraying processes. The results showed that Ni-based coatings exhibited higher wear resistance than Fe-based coatings. The highest wear resistance showed coating produced by using the NiFeBSi-WC filler material and plasma transferred arc welding deposition process. The hardness was not the only characteristic that affected the wear resistance. In this context, the wear rate of NiFeBSi-WC coating was not in correlation with its hardness, in contrast to other coatings. The different wear performance of NiFeBSi-WC coating was attributed to the different type and morphological features of the reinforcing particles (WC).

336-339

Authors: M.F. VasilacheI. Muscă

The existence of a continuous film of lubricant increases the electrical resistance of the contact that can provide information on the quality of contact’s lubrication. This paper presents some experimental results obtained in the control of the lubricant film presence through the resistive method, in lubricated sliding contact between a spherical roller and a cylindrical disc, with the interpretation which gives indications about the time of scuffing.

346-353

Authors: D. Bulut, V. TemizZ. Parlar

The effects of radial force (interface) produced by interference on the static contact properties and frictional characteristics of a radial lip seal are investigated by experimentally. For this reason, a test system has been developed. In this test system, a cylinder is placed on four load cells in order to monitor the friction torque generated between seal and counter face. A group of experiments are carried out with thermoplastic polyurethane radial lip seals. Three different inner diameters (40, 39.80 and 39.60 mm) are selected and the seals are tested under 0.5 and 0.3 bar for a short period. The frictional torque was measured and compared for different inner diameters. As a result, it is observed that the amount of interference effects seal friction torques based on seal material and seal design in different ratios.

360-36

Authors: I.G. Levanov, E.A. Zadorozhnaya, A.L. Dudnikov

The purpose of the article is to develop a tool to assess the theoretical resource crankshaft bearings of internal combustion engine. As a result, two methods for evaluating of the theoretical resource crankshaft bearings have been developed on the basis of the calculation of hydro-mechanical characteristics of bearings: the minimum film thickness and the extent of the zone of boundary friction. Under the theoretical resource of crankshaft bearing it is understood that during his work an increase of the radial clearance in the area of potential exposure (boundary friction) is over the limit. The first technique is based on the bearing life dependence on the ratio between the minimum film thickness and its maximum allowable value. The second technique is based on the molecular-mechanical theory of friction and wear fatigue theory. Thus, these techniques may be used to estimate the resource of the crankshaft journal bearings at the design and finishing stage. However, some parameters of mathematical models have to be determined from the experimental test. The use of molecular-mechanical theory of friction and wear fatigue theory takes into account the influence of the physical and mechanical properties of a bearing material on his life.

374-379

Authors: N.A. Stoica, A. Tudor

The tribological aspects concerning the behaviour of friction materials in the range of low and very low sliding speeds (0.2 – 200 mm/min) are essentially different of those in the high sliding speeds range. This paper aims to study the stick-slip phenomenon which occurs in the range of low and very low speeds. Typically, for the stick-slip phenomenon to occur, the static friction coefficient between the two contact surfaces of the friction materials must be larger than the kinetic friction coefficient. For disc brakes, the stick-slip phenomenon is mentioned in many specialized scientific papers. The phenomenon is manifested through self-induced vibrations. The experimental results were obtained on a dedicated testing machine where the parasite stick-slip motion is reduced through the use of bearings.