Papers by Keyword: Rough Surface

Abstract: Ball bearings are crucial components in various machinery and mechanical systems, finding applications across numerous industries such as automotive, aerospace, manufacturing, robotics, and household appliances. Minimizing friction and wear in the bearings is essential to enhance the efficiency, reliability, and lifespan of equipment. Friction moments in ball bearings occur due to rolling-sliding motion at the ball-race contact and sliding between the ball and cage. The magnitude of these friction moments depends on factors such as surface topography, load, and speed. Understanding how surface topography influences the friction moments in these bearings is crucial. This paper investigates the effect of surface roughness on the friction moment between the ball and race contact, as well as between the ball and cage contact. An analytical model is employed to estimate the friction torque within ball bearings, considering the total friction torque generated at the contact points between the balls and the race, as well as at the ball-cage interface. A mixed elastohydrodynamic lubrication model is used to estimate the friction coefficient at these contact points.

Abstract: The authors proposed a procedure for determining parallel matchmarks in the halftone image of the rough surface. The analysis of micron-scale asperities was carried out in black and white. Relationships between coordinates of variable pixel-value sections of the microasperities under investigation were identified using the correlation analysis. The authors determined the asymmetrical distribution of various grayscales in the image of the polished surface. For that reason, the Spearman’s rank correlation coefficient was found to identify microrelief regularities that enabled to determine peaks of parallel matchmarks available on the rough surface.It is necessary to apply special filtration in order to determine periodicity of linear matchmarks which will remove point inclusions from the surface image (carbides, impurities, impregnated particles, etc.). Small inclusions in the image of the surface being analyzed are considered to be the “noise” while conducting the correlation analysis.The findings are relevant for quality control of optical surfaces. The developed program for calculating the correlation coefficient may be built into a product automatic control system used in bulk production.

Abstract: This paper presents a transient thermal analysis of cold strip rolling, integrating both the microscale asperity deformation and macroscale strip deformation. A statistical characterisation was carried out to obtain the contact pressure and thermal contact conductance at the roll-strip interface. To address the effects of rolling speed and temperature rise, Johnson-cook constitutive model of yielding strength was employed to incorporate the strain rate and temperature variation in the analysis. It was found that the developed model can successfully predict both the interface contact stress and temperature rise in the rolling bite.

Abstract: This paper studies the problem of the relative area changing on a decrease of the load applied to the joint of roughness surfaces. The penetration of a rigid rough sphere (indenter) into the elastic hardenable half-space is initially considered, then the elastic crater restoring by unloading is considered. To defining elastic-plastic material, Hollomon’s power law is used. To describe a contact of a rigid rough surface with an elastic plastic half-space, the discrete model of a rough surface is used. Microasperities are represented as a set of identical spherical segments, the height distribution of which corresponds to the bearing profile curve of the real surface. The dependence the dimensionless force elastic-geometric parameter F_q on a relative amount of indentation ε at loading and the dependence of analogous parameter F_qe on amount of ε-Dε at unloading are obtained. The relations of relative contact areas h and h_e on dimensionless loading F_q and F_qe at loading and unloading for different values of a hardening exponent n and parameter are given. The obtained results are of practical importance for the performance prediction of fixed machine elements’ joints at the design stage, in particular for tightness supply of flange couplings and high pressure vessels seals.

Abstract: This paper shows the results of finite element modelling of contact problems between perfectly rigid body with rough surface and an indenter from elastic-plastic material. In the first phase, spherical indenter from elastic – plastic material is considered, which is pressed into a body with a rough surface. Results show the influence of the amplitude and distances of various undulations at the rough surface to response surface.

Abstract: This article describes a complex and generally applicable computational model for solving the frictional losses of directionally oriented and non-oriented sliding surfaces working under mixed lubrication regime. In the primary phase of this paper are described ways to get characteristics data describing rough surfaces together with the formula for determination of surface pattern directional dependence. Furthermore, formulae describing used contact model are listed and also the structure of the whole powertrain dynamics solution is briefly explained. In the closing section of this paper are shown and discussed results of several types of slide bearing analysis.

Abstract: This paper presents the effect of surface roughness on soft elastohydrodynamic lubrication in circular contact with non-Newtonian lubricant. The time independent modified Reynolds equation, elastic equation and lubricant viscosity equation were formulated for compressible fluid. Perturbation method, Newton-Raphson method, finite different method and full adaptive multigrid method were implemented to obtain the film pressure, film thickness profiles and friction coefficient in the contact region at various the amplitude of surface roughness, surface speed of sphere, modulus of elasticity and radius of sphere. The simulation results showed that the film thickness in contact region depended on the profile of surface roughness. The minimum film thickness decreased but maximum film pressure and friction coefficient increase when the amplitude of surface roughness and modulus of elasticity increased. For increasing surface speeds, the minimum film thickness and friction coefficient increase but maximum film pressure decreases. When radius of sphere increases, the minimum film thickness increases but maximum film pressure and friction coefficient decrease.

Abstract: This paper presents the results of a analysis of rough thermo-elastohydrodynamic lubrication (TEHL) of line contact with non-Newtonian lubricant blended with Al₂O₃ nanoparticles and MoS2 microparticles. The simultaneous systems of time independent modified Reynolds equation, elasticity equation, load carrying with micro particle equation and energy equation were solved numerically using multigrid multilevel with full approximation technique. In this study, the effect of Al₂O₃ nanoparticle and MoS₂ microparticle additives and surface roughness were implemented to obtain film thickness, film pressure, film temperature, friction coefficient and load carrying with microparticle in the contact region. The simulation results showed that the maximum film temperature and friction coefficient increase slightly but the minimum film thickness decreases slightly with an increase in Al₂O₃ nanoparticle concentration due to thermal enhancement of nanofluid. For increasing of microparticle concentration, the minimum film thickness and friction coefficient decrease because the increasing of friction heating of MoS₂ microparticle.

Abstract: This paper presents the performance characteristics of rough thermo-elastohydrodynamic lubrication (TEHL) with non-Newtonian liquid–solid lubricant based on a Power law viscosity model. The time independent modified Reynolds equation, elasticity equation and energy equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel methods were used to obtain the film pressure profiles and film thickness in the contact region. The effects of amplitude of surface roughness and concentration of solid particles are examined. The simulation results showed surface roughness has rapidly effect on film pressure and film temperature. The effect of solid particle can be increases film thickness and decreases friction coefficient.

Abstract: Material removal rate (MRR) distribution is a major concern in CMP process. In the published literatures, both experimental and theoretical research, MRR distribution is given without considering the surface profile of wafer. In this paper, the effect of surface profile on the MRR is analyzed based on the Preston equation and the contact pressure distribution calculated by the mixed lubrication model. It is found that the MRR distribution is dramatically affected by the profile of wafer surface, and whatever the polishing pad is conditioned in situ, the MRR distribution will be uniform at last. In addition, the wear of the pad surface induces a decrease of MRR.