Current Issue : July - September Volume : 2019 Issue Number : 3 Articles : 5 Articles
The surfaces of two engineering polymers including polyamide 66 (PA66) and\npolytetrafluoroethylene (PTFE) were treated by diffuse coplanar surface barrier discharges in\natmospheric air. We found that plasma treatment improved the adhesion of PA66 for either\npolymer/polymer or polymer/steel joints, however, it was selective for the investigated adhesive\nagents. For PTFE the adhesion was unaltered for plasma treatment regardless the type of used\nadhesive. Tribological properties were slightly improved for PA66, too. Both the friction coefficient\nand wear decreased. Significant changes, again, could not be detected for PTFE. The occurred\nvariation in the adhesion and tribology was discussed on the basis of the occurred changes in surface\nchemistry, wettability and topography of the polymer surface....
Analytical solutions describing free transverse vibrations with large amplitude of axially loaded Eulerâ??Bernoulli beams for various\nend restrains resting on a Winkler one-parameter foundation are obtained using the Adomian modified decomposition method\n(AMDM). The AMDM allows the governing equation to become a recursive algebraic equation, and, after some additional simple\nmathematical operations, the equations can be cast as an eigenvector problem whose solution results in the calculation of natural\nfrequencies and corresponding closed-form series solution of the mode shapes. Important to the use of the Adomian modified\ndecomposition method is the treatment of the nonlinear Fredholm integral coefficient, which forms part of the governing\nequation. In addition to the calculation of natural frequencies and mode shapes, investigations are made of the effects on the free\nvibrations of the Winkler parameter and of increasing the axial loading....
Increasing the lifetime of machine elements whose operation involves the development\nof friction processes and diminishing energy losses by friction can be achieved by using solid\nlubricants. In this regard, a method applied to improve the friction behavior of machine elements is\nelectrostatic coating of the surfaces of interest with polyester layers that include particles of solid\nlubricants, such as molybdenum disulfide or graphite. Experimental research was conducted to\nhighlight the influence of normal force, the concentration of solid lubricant particles in polyester,\nand specific sliding between surfaces involved in the friction process on the deposited layerâ??s\nlifetime and on the friction coefficient. Grey analysis was employed to identify sets of input factors\nthat would lead to the most convenient values of the lifetime and energy friction losses when using\npolyester layers that incorporate molybdenum or graphite particles. Specialized software was\nelaborated in a MATLAB environment to use the grey relational analysis in identifying the optimal\nvalues of the process input factors for distinct weights of the output parameters....
In the present study, PA6 polymers with and without solid lubricant inclusions were\ninvestigated against S1100QL steel surfaces that had different surface roughness values-a very\nhigh surface roughness (Rz approximately equal to 40 micron) and a low surface roughness (Rz approximately equal to 5 micron). Static and dynamic\nfriction coefficients were analysed under a series of nominal contact pressures (2.5 to 40 N/mm2)\nconsidering the influences of polymer water saturation, temperature, counter-body surface roughness\nand lubrication. Mechanisms for the observed influences of the respective parameters are provided\nand are interpreted from the view of the adhesive and deformative contributions to the friction force....
MoSN/MoS2 multilayer films were deposited by a sputtering MoS2 target in alternate\nAr and Ar/N2 mixed atmospheres with different nitrogen flow rates. The influence of nitrogen\nflow rates on the microstructure, mechanical and tribological properties of the prepared films were\ninvestigated. The multilayer film exhibited the preferred orientation of (002) plane for MoS2 sublayers\nand amorphous structure for MoSN sublayers. Introducing N2 into the source gas resulted in a much\nmore compact structure for multilayer films due to the suppression of columnar growth of MoS2 film.\nWith the increase of the nitrogen flow rate, the hardness of the multilayer film firstly increased from\n2.3 to 10.5 GPa as the nitrogen flow rate increased from 4 to 10 sccm and then turned downwards\nto 6.5 GPa at 20 sccm. MoSN/MoS2 film deposited with an optimized microstructure exhibited\nlow friction coefficients below 0.03 and a wear life higher than 1.8*10^5 revolutions in vacuum.\nMeanwhile, the optimized film showed an ultralow friction coefficient of 0.004-0.01 and wear rate\nof 4.7 * 10^-7 mm3/N.m in an ultrahigh vacuum. Both the enhanced hardness by N-doping and\nsustainable formed MoS2 tribofilm contributed to the improved tribological property of MoSN/MoS2\nmultilayer film.....
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