Mongkolwongrojn, Mongkol

Preferred name

Alternative Name

Mongkolwongrojn, M.

Main Affiliation

School of Engineering

mongkol.mo@kmitl.ac.th

Now showing 1 - 10 of 13

Some of the metrics are blocked by your
consent settings
Influence of surface roughness in TEHL with non-Newtonian liquid/solid lubricants under sudden load change
(2008-05-16)
Mongkolwongrojn, Mongkol
;
Aiumpornsin, Chatchai
This paper describes the influence of surface roughness on thermoelastohydrodynamic (TEHL) lubrication characteristics of a sliding line contact under sudden load change. The surface roughness is a harmonic wave in the transverse direction. The time-dependent Reynolds equation with non-Newtonian liquid-solid fluids has been formulated using a power law model. The constitutive equation of the liquid-solid lubricants was formulated based on experimental data. The simultaneous systems of modified Reynolds, elasticity and energy equations with initial conditions were solved numerically. The static and dynamic characteristics of the thermoelastohydrodynamic line contact with rough surfaces under sudden load change have been investigated numerically to determine the distribution of pressure, film thickness and temperature. The transient response of the lubricated line contact between a infinitely long cylinder surface and a flat plate was simulated under a heavy step load function. This simulation showed a significant effect of surface roughness and solid particles on thermoelastohydrodynamic lubrication under sudden load change. Copyright © 2007 by ASME.
Some of the metrics are blocked by your
consent settings
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.
Some of the metrics are blocked by your
consent settings
Elastohydrodynamic lubrication of rough surfaces under oscillatory line contact with non-newtonian lubricant
(2008-09-01)
Mongkolwongrojn, Mongkol
;
Wongseedakaew, Khanittha
;
Kennedy, Francis E.
This paper presents the results of a transient analysis of elastohydrodynamic lubrication (EHL) of two parallel cylinders in line contact with a non-Newtonian lubricant under oscillatory motion. Effects of the transverse harmonic surface roughness are also investigated in the numerical simulation. The time-dependent Reynolds equation uses a power law model for viscosity. The simultaneous system of modified Reynolds equation and elasticity equation with initial conditions was solved using the multigrid, multilevel method with full approximation technique. The film thickness and the pressure profiles were determined for smooth and rough surfaces in the oscillatory EHL conjunctions, and the film thickness predictions were verified experimentally. For an increase in the applied load on the cylinders or a decrease in the lubricant viscosity, there is a reduction in the minimum film thickness, as expected. The predicted film thickness for smooth surfaces is slightly higher than the film thickness obtained experimentally, owing primarily to cavitation that occurred in the experiments. The lubricant film under oscillatory motion becomes very thin near the ends of the contact when the velocity goes to zero as the motion direction changes, but a squeeze film effect keeps the fluid film thickness from decreasing to zero. This is especially true for surfaces of low elastic modulus. Harmonic surface roughness and the viscosity and power law index of the non-Newtonian lubricant all have significant effects on the film thickness and pressure profile between the cylinders under oscillatory motion.
Some of the metrics are blocked by your
consent settings
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.
Some of the metrics are blocked by your
consent settings
Lubrication and wear of artificial knee joint materials in a rolling/sliding tribotester
(2007-04-01)
Kennedy, Francis E.
;
Van Citters, Douglas W.
;
Wongseedakaew, Khanittha
;
Mongkolwongrojn, Mongkol
This paper describes the influence of lubrication on wear during testing of materials for artificial knee joints in a rolling/sliding tribotester built to simulate contact conditions in a total knee replacement. The test configuration consists of parallel cylinders (pucks) of ultrahigh molecular weight polyethylene (UHMWPE) and polished cobalt-chrome alloy in oscillatory rolling/sliding contact in a bath of dilute (25%) bovine serum. Wear tests of three different UHMWPE materials were run under constant load at 40% sliding for 1.5 million oscillation cycles at 1.5 cycles/s. Wear of the UHMWPE was determined by measuring the profile of the cylindrical contact surface of the puck before and after each test. Profile measurements were repeated after at least 53 days to eliminate the contribution from creep. Differences between initial and final profiles were attributed to wear of the UHMWPE. It was found that the largest wear depth in the lubricated tests occurred near the ends of the oscillatory contact area, while dry (unlubricated) tests of the same materials showed a peak wear depth near the center of the contact area. In the lubricated tests, the worn depth was lowest for the most heavily irradiated material. Analysis of the elastohydrodynamic lubrication in the rolling/sliding contact was carried out assuming a line-contact situation with smooth cylindrical surfaces. The time-dependent modified Reynolds equation and the elasticity equation with initial conditions were solved numerically using a multigrid technique with full approximation scheme, and using a Newton Raphson method to solve the highly nonlinear system of equations. The thickness of the lubricating film of bovine serum was determined for points along the length of the wear track. It was found that the smallest film thickness (h<inf>min</inf>) occurs very close to the location in the oscillating contact where the greatest wear occurs, owing to the very low entraining velocity near the ends of the oscillation cycle. The coefficient (K) for wear of the UHMWPE was found to be relatively constant over the central section of the oscillatory motion, but increased to a higher value where h<inf>min</inf> decreased to near zero. Thus, the important influence of lubrication on wear of artificial knee bearings was demonstrated. Copyright © 2007 by ASME.
Some of the metrics are blocked by your
consent settings
Influence of indium addition on characteristics of Sn-0.3Ag-0.7Cu solder alloy
(2009-10-19)
Kanlayasiri, Kannachai
;
Mongkolwongrojn, Mongkol
;
Ariga, Tadashi
Effects of indium (In) addition on solidus and liquidus temperatures, wetting time, wetting force, tensile strength, and microhardness of Sn-0.3Ag-0.7Cu lead-free solder alloy were investigated in this paper. Indium was added and varied from 0 to 3 wt%. It is found that solidus and liquidus temperatures of the solder alloy are lowered as the In content is increased. However, In also increases the melting range between solidus and liquidus temperatures. Wetting time of the solder alloy is reduced by the addition of In while the wetting force is increased with the increase of In content. With the addition of In, the Sn-rich phase is smaller in size, and the intermetallic compounds are more uniformly distributed. As a result, tensile strength and microhardness of Sn-0.3Ag-0.7Cu are increased when In is added into the solder alloy. © 2009 Elsevier B.V. All rights reserved.
Some of the metrics are blocked by your
consent settings
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.
Some of the metrics are blocked by your
consent settings
Elastohydrodynamic lubrication of cylindrical roller in line contact
(2004-09-27)
Mongkolwongrojn, Mongkol
;
Yawong, Somnuk
Elastohydrodynamic lubrication is defined as thin film lubrication considering the elastic deformation of material under contact stress. This paper presents the application of finite difference and Newton Raphson method to calculate the Reynolds equation of a cylindrical roller on flat surface numerically. The lubricant is a compressible fluid and operated at isothermal condition. Calculation results show that the film pressure of the lubricants in line contact under elastohydrodynamic lubrication is decreased when the increase of load, on the other hand, the film thickness will be increase as the velocity increase. At severe conditions, the film pressure will be increased approach the Hertzian contact pressure. At constant load and velocity the film pressure increase gradually at lubricant inlet and reach the maximum pressure to form pressure spike at minimum film thickness.
Some of the metrics are blocked by your
consent settings
Compensation and estimation of friction by using extended Kalman filter
(2006-12-01)
Gomonwattanapanich, Opart
;
Pattanapukdee, Adual
;
Mongkolwongrojn, Mongkol
A friction exists in every mechanical system. The phenomenon of friction is complicated and difficult to measure the exact value. In this paper, the compensation and estimation of friction by using Extended Kalman Filter (EKF) have been introduced and investigated. The study plant is a second order system with low-pass PD controller. The actual friction of the plant is assumed to be the modified Tustin friction model. The simulations are conducted for three cases of the input signal: sinusoidal, triangular, square, and two cases of compensation: no friction compensation and with friction compensation. The performances of the system are indicated by root-mean-square error (RMS Error) and peak error (Peak Error). The studies show that the system with the friction compensation by using EKF has the better performances than the system with no friction compensation. The RMS Errors of the system are decrease by 90.4 %, 89.2 %, and 12.5 % for sinusoidal, triangular, and square input signals, respectively. Also, the Peak Errors are decrease by 65.9 % and 58.7 % for sinusoidal and triangular input signals, respectively. For square input signal, there is no significant decrease of the Peak Error due to the high overshoot of the system with friction compensation. © 2006 ICASE.
Some of the metrics are blocked by your
consent settings
Theoretical investigation in thermoelastohydrodynamic lubrication with non-newtonian lubricants under heavy load change
(2004-01-01)
Mongkolwongrojn, Mongkol
;
Thammakosol, Kasame
The time-dependent thermal compressible elastohydrodynamic (EHD) lubrication of 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 power law's model. In this study, the non-Newtonian dilatant fluids for liquid-solid lubricants have been purposed experimentally using the common solid particles namely, Molybdenum disulfide (MoS<inf>2</inf>) and Polytetrafluoroethylene (PTFE). The simultaneous systems of modified Reynolds and elasticity and energy equations with initial conditions were solved numerically using multigrid multilevel technique. The performance characteristics of the thermoelastohydrodynamic under line contact were presented with varying time for the pressure distribution, temperature distribution and oil film thickness. The transient response of the line contact between two surfaces was simulated under a heavy step load function. The coefficients of friction were also presented in this work at steady state condition with varying particle concentration. This simulation showed a significant effect of liquid-solid on thermoelastohydrodynamic (TEHD) lubrication under heavy load conditions. Copyright © 2004 by ASME.

Mongkolwongrojn, Mongkol

Filters

Settings

Sort By

Results per page