Papers by Keyword: Sliding Friction

Abstract: The results of an experimental study of damage for the structural material MoNiCa (it is high-strength cast iron VCHTG – patent of the Republic of Belarus № 15617) on sliding friction and mechano-sliding fatigue are analyzed in the report. Tests of the mechanical system shaft (a sample with a working part diameter of 10 mm made of 0.45 % carbon steel) - an insert (a prismatic counter sample with a cross section of 10 ´ 10 mm made of MoNiCa) were carried out. The kinetics of the change in average wear at 8 local points along the perimeter of the dangerous area of the sample is given for contact loads F_N from 20 to 92 N of the mechanical system under study with MoNiCa inserts without heat treatment and with heat treatment. The test results of the system under study are also presented in the form of sliding friction and mechano-sliding fatigue curves in coordinates of the contact load F_N – the number of cycles N until the limit state.

Abstract: High temperature applications of self-lubricated sliding surfaces have gained industrial importance during the recent years. One popular system is based on sintered Ni-Cr composites with addition of solid lubricants. In the present work these composites were prepared under controlled sintering conditions with different combinations of solid lubricants (MoS₂, Ag and CaF₂) at 1200 °C under flowing argon. The physical properties such as sintered density, relative density and porosity were studied. The microstructures and phase studies of the Ni-Cr based composites were conducted using SEM analysis while the hardness of the composites was measured by Vickers Micro Hardness Tester. The friction tests were conducted with ball on disc configuration following ASTM G-99-95a standard. The MoS₂ solid lubricant provides best lubrication at room temperature which is demonstrated by a low friction coefficient compared to pure Ni-Cr composites. The SEM pictures of worn out tracks show solid debris distribution, and filling of pores with solid lubricant phases. The time taken for stabilization of friction coefficient also varies with the type of solid lubricant. Dual and multiple additions of solid lubricants are also able to reduce the friction of coefficient compared to pure Ni-Cr composite.

Abstract: The paper presents the results of comparative tribological tests of diamond-like inserts. Methods of tribological tests on different tribological units are described. The results showed that a higher content of polycrystalline diamond in the insert improves the anti-wear and anti-friction properties of the composite.

Abstract: The present study includes a detailed analysis of titanium based composite foam developed by powder metallurgy route and to understand the role of process parameters and the particle size of the space holder (cenosphere) on the kinetics and mechanism of wear. Cenosphere of varying particle size (<150 μm; 150-212 μm; > 212 μm) were mixed with titanium in a ratio of 1:3, compacted at 100 MPa and sintered at 1000°C and 1200°C for a period of 2,4 & 6 hrs in each temperature. The kinetics of wear and frictional coefficient of sintered composites were evaluated by reciprocating wear testing machine against diamond indenter at applied load of 10 N. The mechanism of wear was studied by a detailed analysis of the post wear microstructure. The composite foam with cenosphere particle size in the range of 150-212 μm showed minimum wear rate. The mechanism of wear was found to be a combination of adhesive and abrasive.

Abstract: The Ce doped Strontium Magnesium silicate phosphor Sr₂MgSi₂O₇:Ce is compounded by using high temperature roasting process, and the plane sample of prepared phosphor is obtained by tablet press method. A modified MCJ-01A friction tester with the friction pair of glass bar against on the plane phosphor sample is used to determine the triboluminescence property of Ce doped Strontium Magnesium silicate phosphor in the linear contact sliding friction. Examination on the triboluminescence of Ce doped Strontium Magnesium silicate phosphor indicates that a quality triboluminescent phosphor with 448nm± blue spectrum emission can be obtained only in the 1200°C calcining temperature, and only 0.010 molar Ce doping concentration in the Sr₂MgSi₂O₇:Cex can promote the prepared phosphor to generate a higher triboluminecent emission and a smaller full width at half maximum (FWHM). The suitable level of applied load is beneficial to hold a balance between wear increment and spectrum intensity. Finally a triboluminescent unit with squirrel cage structure is constructed to realize the triboluminescence of multiple glass bars against on the cylindrical phosphor in the manner of sliding friction. This can satisfy the light emitting of 360o azimuth, and generate more tribological luminous flux.

Abstract: Using of bearings and gearings is the most prevalent way to transform the momentum in mechanics, however their modular applications, namely – bearings as supports and gearings as transmissions have mutually exclusive weaknesses. This article analyze the jointing of rolling bearings and gearings as one unit, their types, difference and parameters variations, the profits of such constructions, the using of their assemblies and realizations ways.

Abstract: In the experiment reported in this paper, the friction coefficient (μ) and the mass loss of the metal matrix composite obtained from a powder mixture of Mg, Ti and Al sintered at 640, 650 and 660^ºC, with the other parameters held constant, were determined in the dry sliding test at the total distance of 120 m. The sliding speeds of 0.06, 0.09 and 0.14 m/s, and the loads of 2.3, 5 and 9.3 N were applied, as well as a slider made of the EN-GJL300 cast iron. The value of the friction coefficient decreased with the speed and the load, and, for most of the applied friction parameters, it was very low (0.025-0.2). Some influence of the sintering temperature on the mean value of μ and the profile of μ versus the friction distance curve was revealed, yet in the case of the lowest friction speed and load only. An increase of the composite mass loss with the load was revealed, but the wear was generally very low. For a characterization of the composite and its surface after tribological tests, a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) was employed. On the worn surface, effects of abrasion and deformation were visible, but no Ti particle degradation or pulling out were found.

Abstract: Friction is a crucial issue for the performance of a machine with sliding mechanism. While the sliding surface is often manually scraped to improve its tribological properties, the quality is not stable nor the efficiency of the scraping process. This study investigated the influences of micro-scale circumferential grooves on the frictional characteristics of a sliding surface through theoretical analysis and numeric simulations. The study found that sliding surface with micro grooves can reduce the friction, compared to plain surface. An in-depth analysis indicated that the slider with micro-scale grooves was uplifted when it slides, thus reduced the sliding friction. Moreover, as the amount of lubricant collected on the grooves increased, the friction force decreased with time and approached a stable condition.

Abstract: A real-time temperature measurement system was designed for end-face sliding friction pairs with an infrared (IR) probe and IR thermography installed on it. The approximate temperature of contact surface was measured by the probe while non-contact surface’s temperature distribution was determined with the IR thermography. Two experiments with constant load but varied rotational speeds were carried out, and a preliminary study was made to analyze the variation of temperature in the friction process. Furthermore, the probe data was used as thermal load to calculate the temperature field by the FEM model and the result was verified using IR images. The experimental results showed that the infrared measurement system can detect and record the interface-temperature variation accurately. The probe data showed a good dynamic performance with the variation of friction coefficient. In addition, the calculated temperature field showed good accordance with the IR thermography data.

Abstract: Because of overheat and over wear, the distortion and invalidation will be produced easily in combining friction discs of wet clutch of heavy vehicle transmission system. So the paper studies the sliding friction force of a pair of steel and friction disc, calculates the heat flow density, obtains the heat exchange function with axial symmetry, and establishes the finite element model of temperature field. And then the transient heat field simulation is analyzed, and temperature field distribution curves of combining pairs are obtained. Thus the connection is found between time and temperature along radial and axial direction, and temperature field characteristics are obtained with touch press, relative speed, and sliding time.