• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.208.2-212
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• 1997

In a model based friction comensation for a frictional system,the performance of the system is inflenceed by the selection of the friction model. Especially, when a real plant have dynamic friction characteritics, the compensation of friction with a static friction model may deteriorate the perfomance. For the system we constlucted an adaptiv parameter estimation and friction compensation with a newly introduced dynamic friction model proposed by Canudas et.[1]. The model depicts varios frictional phenomena,such as Stibeck effect,frictional memory, Stick-slip motion. Parmeter identification algorithm are followed conventional RLSM adaptive rule. The stability for the closed system was proved by the Lyapunov stability. The result say that if a real system have dynamic friction property,the friction compensation with the dynamic friction model will improve the perfomance moreover static friction model based compensation may lead to the system unstable.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.476-480
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• 2003

This paper presents an effective method to analyze the dynamic characteristics for the shilling transients of power transmission system using the multibody dynamics, which is composed of subsystem equation, subsystem assemble, and the self-determining technique for the system degree of freedom. Using the advantages of multibody dynamics, the proposed method can be used easily for mathematical models of mechanical systems, such as a power transmission, compared with newtonian method. With this theory, dynamic simulation program was developed. The program can be used to verify system performances, transient phenomena, and other dynamic problems. The simulation of a target system was presented, and its validity was attained by being compared with the previous analysis using newtonian method.

• KSTLE International Journal
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• v.10 no.1_2
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• pp.43-47
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• 2009

Influences of carbonaceous ingredient as a solid lubricant in automotive friction materials on friction properties were studied. Three types of carbonaceous ingredients such as natural graphite, artificial graphite, and cokes were mixed using a constrained mixture design. A 1/5 scale brake dynamometer was used to obtain tribological properties. Results showed that cokes substantially increased the friction coefficient, and natural graphite effectively reduced stick-slip phenomena. This significant difference was attributed to the formation of the friction film on the brake pad which was shown to be strongly dependent on the graphite types. The different crystal structures of the carbonaceous solid lubricants played a significant role in the formation of friction film at the interface.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.935-941
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• 1998

Experiments were carried out for a cubic cavity flow. Contrinuous shear stress is supplied by driven flow for high Reynolds number and three kinds of aspect ratios. Velocity vectors are obtained by PIV and they are used as velocity components for Poisson equation for pressure, Related boundary conditions and no-slip condition at solid wall and the linear velocity extrapolation on the upper side of cavity are well examined for the present study. For calculation of pressure resolution of grid is basically $40{\times}40$ and 2-dimensional uniform mesh using MSC staggered grid is adopted. The flow field within the cavity maintains a forced-vortex formation and almost of the shear stress from the driving inflow is transformed into rotating flow energy and the size of the distorted forced-vortex increases with increment of Reynolds number

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.33-39
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• 1996

A theoretical study of the forced vibration response of a cantilevered beam with non-linear dry friction damping is analyzed by various slip displacements and force levels for the position coordinates of spring-mass-damper and external exciting force. A component mode analysis is carried out based on the constraint conditions and Lagrange multipliers to treat physical systems with non-linear damping. The analysis has shown that the basic phenomena observed for a simply supported beam with a dry friction damper attached are also observed for cantilevered beam.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.175-181
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• 2004

This paper presents the main method to analyze the dynamic characteristics of power transmission system using the multi-body dynamics, which is based on the concept of subsystem equation, subsystem assembling, and the self-determination technique for the system degree of freedom. We can model the mechanical components of power transmission system easily with the advantage of multi-body dynamics. Based on the theory, a dynamic simulation program was developed to analyze system performances, transient phenomena, and other dynamic problems. The driving performance of automatic transmission was simulated with using the multi-body dynamics and Newtonian method, and the validity of program was proved by comparing the two kinds of result.

• Bulletin of the Society of Naval Architects of Korea
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• v.10 no.2
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• pp.9-18
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• 1973

The effects of carburization on the fatigue strength and cracks were studied. The fatigue phenomena of the carburized specimens were compared with noncarburized specimens those were either heat-treated or un-treated. The fatigue strength of these specimens were measured by rotating bending fatigue machine. The obtained results indicated that the fatigue strength of carburized specimens were increased ranging from 24-59 % than those of un-treated, and 22-38% than those of heat-treated. The Vickers hardness of carburized were also increased as much as 138-195% than those of un-treated, and 42-125% than those of heat-treated. The microscopic observation of the carburized specimens mostly composed of minute pearlitic structure at hard case exhibited to have more localized slip than those of non-carburized specimens.

• Computers and Concrete
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• v.1 no.1
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• pp.31-46
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• 2004

A methodology is presented for computing stresses in structural concrete members exposed to fire. Coupled heat and moisture migration simulations are used to establish temperature, pore pressure, and liquid-saturation state variables within near-surface zones of heated concrete members. Particular attention is placed on the use of coupled heat and multiphase fluid flow simulations to study phenomena such as moisture-clogging. Once the state variables are determined, a procedure for combining the effects of thermal dilation, mechanical loads, pore pressure, and boundary conditions is proposed and demonstrated. Combined stresses are computed for varying displacement boundary conditions using data obtained from coupled heat and moisture flow simulations. These stresses are then compared to stresses computed from thermal analyses in which moisture effects are omitted. The results demonstrate that moisture migration has a significant influence on the development of thermal stresses.

• Corrosion Science and Technology
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• v.7 no.4
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• pp.237-242
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• 2008

Physical properties of water, such as dielectric constant and ionic product, significantly vary with the density of water. In the supercritical conditions, since density of water widely varies with pressure, pressure has a strong influence on physical properties of water. Dielectric constant represents a character of water as a solvent, which determines solubility of an inorganic compound including metal oxides. Dissociation equilibrium of an acid is also strongly dependent on water density. Dissociation constant of acid rises with increased density of water, resulting in drop of pH. Density of water and the density-related physical properties of water, therefore, are the major governing factors of corrosion and environmentally assisted cracking of metals in supercritical aqueous solutions. This paper discusses importance of "physical properties of water" in understanding corrosion and cracking behavior of alloys in supercritical water environments, based on experimental data and estimated solubility of metal oxides. It has been pointed out that the water density can have significant effects on stress corrosion cracking (SCC) susceptibility of metals in supercritical water, when dissolution of metal plays the key role in the cracking phenomena.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.95-105
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• 2012

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia ($NH_3$) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and $NH_3$ slip reduction in the SCR system. This paper investigated NOx and $NH_3$ emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and $O_2$ for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm can not estimate $NH_3$ absorbed on the catalyst. Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated on the numerical model describing physical and chemical phenomena in SCR system. One channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.