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Based on the application of fractal geometry theory, a quantitative evaluation method of root-mean-square wavelength of 3D stochastic surface topography is proposed, by means of the surface spectral moments. Through the FFT of the discrete data of the profile measured by a Talysurf-5 contact stylus instrument, we obtained the power spectrum and the fractal dimension of the profile. Furthermore, the...
Measurements of dry and lubricated sliding for a wide range of elastomers (natural and synthetic) have been carried out using a specially modified British Pendulum Skid Tester. This instrument incorporates an optical position sensor, a high-precision electronic timer, and a computer interface. It monitors the swing of a pendulum at angular intervals of 0.14 o as it drives an elastomer slider...
The effects of cold deformation on the dry sliding wear of RS/PM Al-10 wt.% Ti alloy have been studied at a low sliding speed of 0.66 m/s. It is indicated that the wear mechanism of the RS/PM Al-10 wt.% Ti alloy changes from adhesion to oxidation wear with the increasing applied load. At adhesive wear stage, wear resistance of the alloy decreases with the increase of the residual strain after cold...
The influence of the microstructure of WO 3 thin films upon friction and wear during sliding contact was studied using two different tribometers. The tungsten trioxide (WO 3 ) thin films of controlled microstructure were grown on R-plane sapphire substrates using electron cyclotron resonance (ECR) oxygen-plasma-assisted electron beam evaporation of WO 3 pellets. The WO ...
Along with the advancement of analysis and awareness of the environment has come increasing concern over the effects of petroleum products being released into it. No doubt, petroleum may be released to the environment as a potentially harmful material. This has promoted the use of environment-friendly lubricants, including additives. In view of this, a study of the effects of a synthesized ester additive...
During sliding between a railway wheel and rail, frictional heat is generated that causes a temperature increase in the surface layer high enough to austenitise it. Due to the rapid cooling that follows when the wheel starts to roll again, martensite often forms in the surface layer. In the present paper, an analytical model of heat conduction in the thermally affected zone (TAZ) is established and...
Two Fe-Cr-B based gas atomized powders, proposed as metamorphic alloys (Armacor M and Armacor 16), were thermally sprayed using the HVOF (High Velocity Oxygen Fuel) process. Armacor M was also weld-surfaced by PTA (Plasma Transferred Arc) process. The resultant deposits were subsequently characterized, using X-ray diffraction, scanning electron microscopy, and microhardness measurement. The wear performances...
During a wheel-rail slide, the temperature is high enough to austenitise the material close to the contact surface. The material is rapidly cooled by heat conduction into the rest of the wheel when the wheelset starts rolling again and thus martensite can form in the surface layer. In the present investigation, the mechanically and thermally affected zones (TAZ) under railway wheel flats have been...
Although the methods of calculation for scoring on gears with hardened and ground tooth profiles have been presented, a calculation method for scoring on gears with hardened but not ground tooth profiles apparently does not exist in the literature. Besides, being a cause of failure, scoring is an important factor in the noisy working of gearsets due to the vibration it causes. In this study, the scoring...
Existing techniques for measuring and characterising anisotropy are discussed. The advantages are suggested in treating anisotropic surfaces as self-affine fractals, characterised by two parameters, the fractal dimension and the topothesy. These parameters are conveniently determined experimentally by measuring the slope and intercept of a logarithmic plot of the structure function. A 3D version of...
A correlation between low-cycle fatigue (LCF) life and scuffing-failure life as well as wear rate is demonstrated using the plastic strains in three stages of boundary lubricated sliding. Constant loading and proportional loading, which was proportional to hardness with three different lubricated conditions, were used to evaluate the plastic strain. From the results of constant loading tests, it was...
The main goal of this work is to study the influence of the relative positions of tool and workpiece on tool life and on surface finish of the workpiece in the process of face milling flat surfaces. Aiming to achieve this goal, several milling experiments were carried out with different relative positions of tool and workpiece. The tool flank wear and the surface roughness of the workpiece were measured...
Dry sliding friction-induced subsurface deformation of elemental aluminium alloy AA6061 and AA6061-based Saffil fibre-reinforced composites, manufactured by a powder metallurgy (PM) route, was investigated using both the microhardness and strain gradient measurement techniques. Under the same applied load, a greater depth of the deformation zone was found in the composite than in the base alloy. Compared...
Features of contact spots heating are considered when electric current passes through the metallic interface. Relationships are presented for contact temperature evaluation at different mechanisms of current passage. Emphasis is put on the contact with thin (nanometer scale) boundary films. The analysis indicates that the method of local heating of the contact zone by electric current can be used...
In the present paper a model for the fast numerical prediction of the friction coefficient and the temperature field of such contacts is introduced. Motion and energy equations are numerically solved taking into consideration the non-Newtonian behavior of the lubricant assuming a power law rheological model. The viscosity is calculated in every point of the film as a function of the local temperature...
The tribological properties of a binderless carbide (BL) have been evaluated in abrasion and sliding wear tests. Conventional cemented carbides and ceramics were used as reference materials. The worn surfaces were studied with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Transmission electron microscopy (TEM) and SEM were used to analyze the microstructure of...
Hexagonal boron nitride (BN) has a graphite-like lamellar structure, but has been considered less effective than other solid lubricants except for high-temperature applications. The present paper describes a series of sliding experiments which show somewhat curious behavior of BN when added to lubricating oil, and discusses their results by comparing with the results of observation and analysis of...
Experiments [N. Mittwollen, T. Hegel, J. Glienicke. Effects of hydrodynamic thrust bearings on lateral shaft vibrations, Journal of Tribology, 113 (October 1991) 811-818] have shown that hydrodynamic thrust bearings may influence lateral rotor vibrations significantly. The purpose of this study was to develop fast computational routines to evaluate the main dynamic coefficients for hydrodynamically...
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