Mongkolwongrojn, Mongkol

Preferred name

Alternative Name

Mongkolwongrojn, M.

Main Affiliation

School of Engineering

mongkol.mo@kmitl.ac.th

Now showing 1 - 10 of 15

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Transient EHL of two surfaces under elliptical contact with non-Newtonian lubricant
(2012-02-23)
Mongkolwongrojn, Mongkol
;
Panichakorn, Jesda
This paper presents the effects of a sudden load change and sudden speed change on the performance characteristics of two surfaces under elliptical contact with elastohydrodynamic lubrication. The non-Newtonian lubricant for the research work are modeled based on Carreau viscosity model. The time dependent modified Reynolds equation and elastic equation were formulated for compressible fluid. Perturbation method, Newton Raphson method and full adaptive multigrid method were implemented and solved to obtain the film pressure, film thickness profiles and friction coefficient in the contact regime at various applied loads and speeds. Simulation results show the friction coefficient increase significantly under sudden loads. The minimum film thickness and friction coefficient both decrease significantly as speed is decreased. © (2012) Trans Tech Publications.
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Transient elastohydrodynamic lubrication in artificial knee joint with non-Newtonian fluids
(2010-05-01)
Mongkolwongrojn, Mongkol
;
Wongseedakaew, Khanittha
;
Kennedy, Francis E.
This paper presents the transient analysis of a human artificial knee joint under elastohydrodynamic lubrication (EHL) for point contact with non-Newtonian lubricants. The artificial knee joints use ultra high molecular weight polyethylene (UHMWPE) against metal with time-varying speed and load during walking. This numerical simulation employed a perturbation method, Newton Raphson method and multigrid method with full approximation technique to solve simultaneously both the time-dependent Reynolds equation, with non-Newtonian fluid based on a Carreau model, and the elasticity equation. The general numerical schemes are implemented to investigate the characteristics of elastohydrodynamic lubrication in human artificial knee joints; profiles of pressure and film thickness are determined, with varying material and lubricant properties, applied loads and speeds. The results show that the elastohydrodynamic fluid film thickness between the metallic component of the artificial knee joint and the soft polyethylene bearing becomes larger as the contact area increases and the fluid film pressure decreases. At the beginning of the first walking cycle, the film thickness is lower than in subsequent cycles because of the time required to develop the fluid film; after the first cycle, the fluid film is similar for every cycle and is dependent on transient applied load and speed during human movement. © 2009 Elsevier Ltd. All rights reserved.
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Effect of Al2O3 nanoparticles additives on thermo-elastohydrodynamic with Newtonian lubricant
(2013-10-04)
Rattapasakorn, Sountaree
;
Mongkolwongrojn, Mongkol
This paper presents the effect of Al<inf>2</inf>O<inf>3</inf> nanoparticles additives on thermo-elastohydrodynamic with Newtonian lubricant. The modified Reynolds equation and energy equation have been formulated and solved numerically with initial conditions using multi-grid multi-level method. Simulation results show the operating with Al<inf>2</inf>O<inf>3</inf> nanoparticles blended particularly with SAE-90 lubricant. The maximum pressure and temperature decreases, as compared to SAE-90 oil without nanoparticles additives. © (2013) 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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Influence of speed-up and speed-down on internal stresses of wound rolls in web handling process
(2012-02-23)
Mongkolwongrojn, Mongkol
;
Jeenkour, Puttha
In web winding process, the effects of speed-up and speed-down on internal stresses of wound roll have been investigated. The air-entrainment can be obtained theoretically using the modified nonlinear Hakiel model. In this research work, air-entrainment model established by Hamrock and Dowson was applied to estimate the initial air film layers into a wound roll in the winding system with a nip-roller. Moreover, the characteristics of a wound roll were examined under varying tension and varying speed conditions. The numerical results showed the radial stress, tangential stress, and friction force distributions at central inside a wound roll under the condition for a wound roll without wrinkle and slippage phenomena. © (2012) Trans Tech Publications.
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Study swaging process for reduction swage effect in hard disk drive
(2013-04-15)
Bamrungwongtaree, Joompondej
;
Mongkolwongrojn, Mongkol
In hard disk drive manufacturing common uses ball swaging. It is a process that used to assemble a boss tower and an arm aperture. The swage ball has a larger diameter than an inner diameter of the boss tower. Application a compression force to the inner surface of the boss tower to hold both components together with adequate holding force and without damaging the boss tower components result in HGA torque retention. Measurements of HSA KPIV after swaging obtained from deformation of base plate and arm pad together. Due to hard disk drive is dynamically developed by increasing in the areal density and reducing in size, thus the arm pad is thinned. This study focuses on reducing of the swage effect by control outer arm pad deformation to maintain HSA performance. HGA torque retention was considered to reduce gap to arm and to avoid HSA resonance while swaging quality was similar. The 3-D FE method was used for analysis. The analysis and experiment show that HGA torque retention and the arm aperture modified was almost linear. Furthermore, the reduction of arm deformation and gap to arm cause increasing in HSA performance. The arm aperture can be modified for manufacturability. © (2013) Trans Tech Publications, Switzerland.
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Theoretical analysis of flying characteristics for air-helium filled HDD
(2014-01-01)
Mongkolwongrojn, Mongkol
;
Kuanoon, Kunchit
This paper presents the flying characteristics of air-helium filled hard disk drive for a self-acting two rails flat slider bearing. Numerical scheme based on the finite difference with multigrid multi-level technique were implemented for the ultra-low flying height sliders. The characteristics of air-helium filled HDD have been examined in this research work. The results shown that the change of flying height is significantly for various fraction of air-helium filled, at various operating conditions such as temperature velocity and mass of slider. Increase of velocity, flying height increase. Increase both the temperature and the mass load, flying height decrease. Increasing of fraction in helium gas, the flying height decreases rapidly for 40% to 60% of fraction in helium filled. The flying height for air-helium filled magnetic flat slider head equal to 1.3 nm at trailing edge with mass load 12 mN and velocity 20 m/s. The spacing for helium filled hard disk drive is lower than 3 nm when compared with conventional air filled hard disk drive. © (2014) Trans Tech Publications, Switzerland.
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Effects of slider geometry change on helium filled HDD
(2014-01-01)
Mongkolwongrojn, Mongkol
;
Kuanoon, Kunchit
This paper describes the static characteristics of helium filled hard disk drive for a s two rails flat slider gas bearing. Numerical scheme based on the finite difference with multigrid multi-level technique were implemented for the ultra-low flying height sliders. The effect of slider geometry change in both crown and camber on flying height have been examined in this research work. The results show that the flying height change is significantly with a few nanometers change in crown and camber. The flying height of helium filled magnetic flat slider head equal to 3.5 nm at trailing edge. The spacing for helium filled hard disk drive is lower than 4 nm when compared with conventional air filled hard disk drive. The increase of slider crown, the flying height increases rapidly but the increase of slider camber, the flying height decreases continuously. © (2014) 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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Stability analysis of rough journal bearings under TEHL with non-Newtonian lubricants
(2010-05-01)
Mongkolwongrojn, Mongkol
;
Aiumpronsin, Chatchai
The combined effects of surface roughness and lubricants rheology on stability of a rigid rotor supported on finite journal bearing under thermal elastohydrodynamic lubrication have been investigated using the transient method. The newly derived time dependent modified Reynolds and the adiabatic energy equations were formulated using a non-Newtonian Carreau viscosity model. The simultaneous systems of modified Reynolds equation, elasticity equation, energy equation, and the rotor motion equation with initial conditions were solved numerically using multigrid multi-level method with full approximation technique. From the characteristic equation, the instability threshold is then obtained with various surface roughness parameters and the elastic modulus of the bearing liner materials. The results show that stability of the bearing system deteriorates with decreasing both the power law exponent and the elastic modulus of bearing liner material. The rough surface journal bearing with transverse pattern under TEHL regime exhibits better stability when compared with the rough surface journal bearing with longitudinal pattern. © 2010.

Mongkolwongrojn, Mongkol

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