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Analysis of two surfaces under viscoelastic contact
(2013-10-25)
Mongkolwongrojn, M.
;
Panichakorn, J.
;
Supawanich, S.
;
Chutima, S.
This paper presents the analysis of the contact surfaces between a rigid cylinder and a soft plate for viscoelastic material. The contact pressure and deformation of the plate in contact region were determined using finite element technique. Moreover, the characteristics of two surfaces of cylindrical roller and plate under elastohydrodynamic lubrication with nonNewtonian fluid were examined using finite difference technique with full adaptive multigrid method. In this study the simulation of viscoelastic material in contact was under taken to determine the effects of material behaviors on the deformation of plate compared to the elastic materials. The results indicated that the deformation shapes were nonlinearly dependent with the applied loads. Furthermore, the deformation of elastic material would reach a certain value in a period of time whereas the deformation of viscoelastic material was increased inconsistently with time. The film pressure and film thickness profiles in the contact regime were investigated at various loads. The minimum film thickness occurs near the trailing edge of contact region and becomes very small under heavy loads. © (2013) Trans Tech Publications, Switzerland.
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Effect of solid particle on TEHL under line contact with solid-liquid lubricant
(2012-04-04)
Rattapasakorn, S.
;
Mongkolwongrojn, M.
The two infinitely long surfaces in line contact under thermoelastohydrodynamic lubrication with solid-liquid lubricants were investigated. The time-dependent modified Reynolds equation elasticity equation and the adiabatic energy equation have been formulated and solved numerically with initial conditions using multi-grid multi-level method with full approximation technique. The characteristics of the two surfaces in line contact under thermoelastohydrodynamic lubrication were presented as; film pressure, film temperature and oil film thickness profiles. The results of solid-liquid lubricants with micro-particle and nano-particle under thermal elastohydrohynamic lubrication were compared with the case of pure liquid lubricant. © (2012) Trans Tech Publications, Switzerland.
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Effects of surface roughness on elastohydrodynamic lubrication in elliptical contact with non-Newtonian fluids
(2012-04-04)
Rattapasakorn, S.
;
Panichakorn, J.
;
Mongkolwongrojn, M.
This paper presents the effect of surface roughness on the performance characteristics of elastohydrodynamic lubrication with non-Newtonian fluid base on Carreau viscosity model in elliptical contact. The time independent modified Reynolds equation and elastic equation were formulated for compressible fluid. Perturbation method, Newton Raphson 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 amplitude of combined surface roughness, applied loads, speeds and elliptic ratio. Simulation results show surface roughness amplitude has significant affected the film pressure in the contact region. The minimum film thickness decreases but friction coefficient increases when the combined roughness and applied loads increases. The minimum film thickness and friction coefficient both increase as the relative velocity of the ball and the plate is increase. For increasing the elliptic ratio, the minimum film thickness increases but the friction coefficient decreases. © (2012) Trans Tech Publications, Switzerland.
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Thermoelastohydrodynamic analysis of journal bearings with non-Newtonian Carreau fluids
(2010-06-24)
Mongkolwongrojn, M.
;
Aiumpornsin, C.
The paper focuses on the solution of a numerical model to explore the journal bearing performance under transient thermal elastohydrodynamic lubrication with non-Newtonian lubricants based on Carreau viscosity model. The newly derived time-dependent modified Reynolds equation and the adiabatic energy equation have been formulated using a non-Newtonian Carreau viscosity model. The simultaneous systems consisting of the modified Reynolds equation, elasticity equation and energy equation with initial conditions were solved numerically using the multi-grid multi-level method with full approximation technique. The analysis showed that the fluid characteristics as defined by the Carreau model, led to large differences in minimum film thickness and maximum temperature rise for bearing liners with low elastic modulus. Copyright © 2009 by ASME.
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Theoretical investigation in thermoelastohydrodynamic lubrication with non-Newtonian lubricants under sudden load change
(2006-10-01)
Mongkolwongrojn, M.
;
Aiumpornsin, C.
;
Thammakosol, K.
The time-dependent thermal compressible elastohydrodynamic lubrication of a sliding line contact has been developed to investigate the effect of a sudden load change. The time-dependent modified Reynolds equation with non-Newtonian fluids has been formulated using a power law model. Properties of non-Newtonian dilatant fluids for solid-liquid lubricants have been studied experimentally using two common solid particles; namely, molybdenum disulfide and polytetrafluoroethylene. The simultaneous systems of modified Reynolds, elasticity, and energy equations with initial conditions were solved numerically using a multigrid multilevel technique. The performance characteristics of the thermoelastohydrodynamic line contact were presented with varying dimensionless time for the pressure distribution, temperature distribution, and oil film thickness. The transient response of the line contact between two infinitely long cylindrical surfaces was simulated under a heavy step load function. The coefficients of friction were also presented in this work at steady condition with varying particle concentration. This simulation showed a significant effect of solid particles on thermoelastohydrodynamic lubrication under heavy load conditions. Copyright © 2006 by ASME.
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Theoretical investigation of transient elastohydrodynamic lubrication with newtonian solid-liquid lubricants
(2006-10-01)
Mongkolwongrojn, M.
;
Thammakosol, K.
This paper reports a theoretical investigation of transient elastohydrodynamic lubrication of a line contact. A time-dependent Reynolds equation and elasticity equations for compressible solid-liquid lubricants were solved using finite volume and multigrid techniques. The lubricants used were mineral oils mixed with very small solid particles, MoS<inf>2</inf> and FIFE which can be treated as Newtonian fluids. The two surfaces were initially at rest and in contact. The transient oil film pressure and oil film thickness were calculated numerically. This simulation showed the significant effects of solid particles on the lubrication characteristics. Copyright © 2006 John Wiley & Sons, Ltd.
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Elastohydrodynamic lubrication analysis of the two surfaces under oscillatory contact with non-newtonian fluids
(2006-01-01)
Wongseedakaew, K.
;
Mongkolwongrojn, M.
Elastohydrodynamic lubrication characteristics of the two surfaces in line contact under oscillatory motion have been theoretically investigated on the effect of both surface materials and non-Newtonian model parameters. The simultaneous system of time-dependent modified Reynolds equation with a power law model and elasticity equation with initial conditions were solved numerically using multi-grid with full approximation scheme and Newton Raphson method for the high nonlinear equations. The performance characteristics of elastohydrodynamic lubrication were presented for the pressure profile and film thickness profiles with varying dimensionless times at various loads and speed conditions. The results showed that both surface materials and non-Newtonian model parameters have significant affect on elastohydrodynamic lubrication of the two oscillating surfaces under heavy loads. Copyright © 2006 by ASME.
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Theoretical characteristics of hydrodynamic journal bearings lubricated with soybean-based oil
(2002-01-01)
Mongkolwongrojn, M.
;
Arunmetta, P.
Vegetable-based oils are not only biodegradable but also environmentally advantageous, and the range of lubrication applications offered by them continues to grow. Recently, vegetable-based oils have been combined with synthetic esters to produce modified vegetable-based oils. This paper presents an investigation of the theoretical characteristics of hydrodynamic journal bearings lubricated with non-Newtonian soybean-based oil. The soybean-based oil was mixed with synthetic esters and silicone oil. The relationship between the shear stress and shear strain rate of the oil was obtained experimentally. The time-dependent modified Reynolds equation including non-Newtonian effects was formulated for short circular journal bearings. The perturbation technique was applied to the Reynolds equation to obtain zero- and first-order pressure equations. The finite difference method was used to calculate the pressure distribution numerically. The static and dynamic characteristics, such as pressure distribution, Sommerfeld number, attitude angle, and spring and damping coefficients, were obtained numerically. It was found that the nonlinear factors of the non-Newtonian soybean-based oil strongly affected the performance characteristics of the journal bearings.
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Transient response of head slider with geometry change in head surface of magnetic storage systems
(2002-01-01)
Mongkolwongrojn, M.
;
Gunnuang, W.
In this study, the dynamic flying characteristics of the worn head sliders are investigated theoretically due to the change in head geometry caused by head and disk contact. The film shapes can be approximated as taper- Truncated cycloidal-flat film. Two-dimensional time dependent modified Reynolds equation included molecular slip effect are formulated with neglected the roughness effect. The motion of head slider was assumed to have two degree of freedom in this work. Finite difference approximation with Newton Raphson iterative technique and the fourth order Runge-Kutta method were implemented to obtain the transient response of the slider head with various change in head geometry numerically and compared with IBM3380 type head The simulation results show the film shape has affects significantly on the static and dynamic characteristic of slider head in magnetic storage systems.
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Adiabatic Approximate Solution for Static and Dynamic Characteristics of Turbulent Partial Journal Bearings With Surface Roughness
(1994-01-01)
Hashimoto, H.
;
Mongkolwongrojn, M.
Hydrodynamic bearings are generally used for a long term, so the bearing surfaces may be roughened for many reasons such as wear, impulsive damage, foreign particles, cavitation erosion, rust, and so on. Under the turbulent operating conditions of high speed bearings, the surface roughness may result in considerable increase in both film pressure and temperature. This paper describes an adiabatic approximate solution for the static and dynamic characteristics of 180 deg partial journal bearings with homogeneous surface roughness. Applying the modified lubrication equation and energy equation, considering the combined effects of turbulence and surface roughness, to the finite width 180 deg partial journal bearings, the static and dynamic characteristics such as pressure and temperature distributions, Sommerfeld number, attitude angle, spring and damping coefficients and whirl onset velocity are obtained numerically. In the numerical analysis of the temperature distribution, adiabatic boundary conditions are assumed and then the heat transfer effect to the journal and bearing-bush surfaces is omitted. The numerical results are indicated in graphic form for various relative roughness under the mean Reynolds number of Re = 5000 and 10,000. Moreover, some numerical results of static characteristics are compared with the experimental results. © 1994 by ASME.

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