A comparison of porous structures on the performance of slider bearing with surface roughness in micropolar fluid film lubrication (original) (raw)
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Tribology Online, 2022
In this paper, an investigation has been made to study the dynamic characteristics of porous inclined slider bearing with rough surface lubricated with micropolar fluid lubricant. On the basis of Eringen's micro-continuum theory, the Reynolds type equation of porous slider bearing is derived by considering rough surface and squeezing action to evaluate dynamic characteristics of slider bearing. Perturbation method has been used for detailed analysis. Reynolds type equations are obtained for steady performance and perturbed characteristics. The solutions of these equations are obtained. According to the results, an increase (decrease) in the load carrying capacity, dynamic stiffness and damping coefficient are observed for the negatively (positively) skewed surface roughness.
European Journal of Mechanics - B/Fluids, 2018
The lubrication theory is mostly concerned with the behavior of a lubricant flowing through a narrow gap. Motivated by the experimental findings from the tribology literature, we take the lubricant to be micropolar fluid and study its behavior in a thin domain with rough boundary. Instead of considering (commonly used) simple zero boundary condition, we impose physically relevant (nonzero) boundary condition for microrotation and perform asymptotic analysis of the corresponding 3D boundary value problem. We formally derive a simplified mathematical model acknowledging the roughness-induced effects and the effects of the nonzero boundary conditions on the macroscopic flow. Using the obtained asymptotic model, we study numerically the influence of the specific rugosity profile on the performance of a linear slider bearing. The numerical results clearly indicate that the use of the rough surfaces may contribute to enhance the mechanical performance of such device.
MICROPOLAR FLUID LUBRICATION OF FINITE PARTIAL ROUGH POROUS JOURNAL BEARINGS WITH SQUEEZE EFFECT
In this paper, the lubrication theory for squeezing with micropolar fluids in smooth surfaces has been advanced to analyze the effects arising from roughness consideration using the stochastic approach. Basing on the Christensen's stochastic model, the stochastic generalized Reynolds equation is deduced. The Christensen stochastic theory of hydrodynamic lubrication of rough surface is used to study the effect of two types of surface roughness on the squeeze film characteristics of a finite partial porous journal bearing with micropolar fluid. It is assumed that, the roughness asperity heights are small compared to the film thickness. The film pressure distribution equation is numerically solved by using the conjugate gradient method of iterations. According to the results, the micropolar fluid effects can raise the film pressure of the lubricant fluid, improve the load –carrying capacity and squeezing effect. The surface roughness effect in the influence of longitudinal or transverse to the journal bearing is in reverse trend.
Tribology Online
In this paper, combined effects of piezo-viscous dependency and surface roughness on the squeeze film characteristics of non-Newtonian micropolar fluid in conical bearings are presented. On the basis of Christensen's theory, two types of one dimensional structure, the longitudinal roughness and transverse patterns are considered. The stochastic modified Reynolds equation for these two types of roughness patterns is derived for micropolar fluid by taking into account variation of viscosity with pressure. Through a small perturbation technique, the analytical approximate solution for the mean fluid film pressure, load carrying capacity and squeeze film time is obtained. According to the results, the combined effects of non-Newtonian and viscosity pressure dependency provide an enhancement in the load carrying capacity and lengthen the response time for both types of roughness patterns as compared to the classical iso-viscous Newtonian lubricant case. On the whole, the squeeze film characteristics of conical bearings is improved especially for higher values of coupling parameter and viscosity parameter.
On The Lubrication of a Rotating Shaft with Incompressible Micropolar Fluid
Topical Problems of Fluid Mechanics 2020, 2020
In this work, we investigate the lubrication process of a slipper bearing. The slipper bearing consists of two coaxial cylinders in relative motion, where an incompressible micropolar fluid (lubricant) is injected in a thin gap between them. We compute the asymptotic approximation of the solution to the governing micropolar system as a power series in terms of the small parameter ε representing the thickness of the shaft. The proposed approximation is given in the explicit form, allowing us to clearly observe the effects of the micropolar nature of the fluid.
Journal of Plastic Film & Sheeting, 2018
The theoretical model of roll coating onto a moving sheet is developed based on micropolar fluid constitutive equations and lubrication approximation. Closed form expressions for velocity, microrotation and pressure gradient are obtained. Runge-Kutta method is used to calculate the engineering quantities of interest such as, pressure, roll-separating (load-carrying) force and power input. The separation point is numerically calculated using Newton’s iterative method together with generalized Leibniz rule. The effects of involved parameters on the pressure gradient, velocity, pressure and other mechanical quantities are displayed through various graphs. Extreme pressure is observed in the nip region for larger coupling numbers and microrotation parameters. This leads to increased load-carrying force and power input for micropolar fluid when compared to a Newtonian fluid. Moreover, the separation point decreases from its Newtonian value with increasing [Formula: see text]
On the Performance of Finite Journal Bearings Lubricated with Micropolar Fluids
Tribology Transactions, 1989
A Study of the performance parameters for a journal bearing of finite lubricated with micropolar fluids is undertaken. Results indicate that ficantly higher load carrying capacity than Newtonian fluids may result ng on the size o f material characteristic length and the coupling I w National Aeronautics and Space Administration 2. Government Accession No.
Effect of slip/no-slip on finite slider bearing using non-Newtonian micropolar fluid
2018
Load Slip Pressure Micropolar fluid Hydrodynamic In this paper, the modified Reynolds equation of finite slider bearing lubricated with micropolar fluid is numerically solved for the computational aspects of the bearings. The finite difference scheme has been employed to solve the governing equations. The effect of micropolar parameter and slip parameter is investigated on slider bearing. For investigating the effect of slip boundary on the pressure distribution in sliding surface is numerically presented in the Reynolds model. The two-dimensional modified Reynolds equation can predict the performance of lubrication process with boundary slip in sliding contact which can be seen by the obtained results. The pressure and load capacity are displayed graphically. The pressure and load carrying capacity is lesser for slip case as compared to no slip case.
Nano-fluid lubrication of single-layered porous hydrostatic bearing: a theoretical approach
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2020
A theoretical framework of single-layered PHB (porous hydrostatic bearing) lubricated by nano-oil has been developed here. The impact of nano-oil on the presentation of said hydrostatic bearing has been concentrated with the assistance of modified Darcy's law and distinctive boundary conditions. The different nanoparticles are utilized as an added substance of conventional lubricants to upgrade its consistency. The statement of dimensionless exhibition attributes of the researched bearing has been determined by utilizing the modified Krieger-Dougherty viscosity model of nano-fluid and modified Darcy's flow model. The outcomes uncovered that the exhibition qualities are fundamentally improved with the utilization of nano-lube oil as contrasted and the equivalent of other Newtonian and micropolar fluids. Thus, the present investigation is validated with perfect covenant.
Facta Universitatis, Series: Mechanical Engineering
The study aims at analyzing the performance of a ferrofluid-based infinitely long rough porous slider bearing which makes use of thin film lubrication at nanoscale. The stochastic model of Christensen and Tonder has been employed to analyze the effect of surface roughness while the Neuringer-Rosensweig’s model has been adopted to study the magnetization effect. The pressure distribution in the bearing system has been obtained by solving the associated stochastically averaged Reynolds type equation. The results indicate that although the transverse roughness is supposed to affect the bearing system adversely, the situation remains fairly better in the case of thin film lubrication at nanoscale. In fact, the consideration of thin film lubrication at nanoscale results in an all round improved performance, even for lower strength of the magnetic intensity. However, the couple stress adds a little more to this positive effect.