• 한국기계가공학회지
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• 제3권2호
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• pp.10-17
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• 2004

A real depth of cut in deformed zone has larger than an ideal depth of cut. So the heat generated during grinding operation makes the deformation of a workpiece surface as convex farm. Consequently the workpiece surface remains a geometric error as concave form after cooling In this study, the grinding force and the geometric error were examined in surface grinding. Through magnitude and mode of geometric error were evaluated according to grinding conditions, an optimal grinding condition was proposed to minimize the geometric error In addition, the relationship between the geometric error and the grinding force was examined. Due to least square regression, It was possible to predict the geometric error by using the grinding force.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.647-653
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• 2000

In this research the heat regenerative technology was employed to eliminate frosting on evaporator coil and improve COP of the heat pump system. This heat regenerative device(HRD) has very simple structure consisting a geared motor and a porous fiber belt passing through alternatively between cold and warm air duct. The laboratory test showed that the heat pump system with HRD yielded an impressive COP higher than 3.5 at the outside air temperature of $-7^{circ}C$ in heating mode.

• Journal of Welding and Joining
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• 제4권2호
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• pp.40-46
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• 1986

This investigation is concerned with the toughness and microstructure of manneristically simulated HAZ in 12% Cr steel. Unnotched specimens were subjected to weld thermal cycles a weld simulator. The parameters-peak temperatures, cooling rate, influence of PWHT and plastic deformation were considered. After weld simulation, the specimens were heat-treated, V-notched and impact tested. An optical metallographic examination was performed to correlate the HAZ toughness with microstructure. Also a fractographic examination was done to obtain information on the fracture mode. The toughness of the coarse grained zone and the part of HAZ subjected to a peak temperature range 700-800.deg. C are lower than the other parts. However, they are still high enough. The double PWHT cycle could not improve the HAZ toughness in present study. However, if the first PWHT is conducted before the work piece is cooled below $M_f$, it is expected that the double PWHA may be beneficial to the toughness of the HAZ. It is also expected that martensitic welding can be used on production welds.

• Journal of Welding and Joining
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• 제6권3호
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• pp.21-26
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• 1988

The behavior of angular distortion in butt joint wleding of thin plate structure is investigated with an experimental model and partially with a computational model. The experimental model studying the effects of specimene size and degree of restraint on the angular distorion offers a good method for analyzing the behavior of the distrotion. In addition, the distrotion during welding was demonstrated by both experimental measurement and numericla prediciton. The facts evealed in this study are as follows : 1) distrotion angles were changed with variations of specimene wldth. 2) With the restraint, angular distrotion was reduced to 20% to that of free joint. 3) After the restraint being removed, the effect of restraint was also remained. 4) Same heat input per unit thickness caused same amount of distortion. 5) The mode of angular distortion was expected to be changed with expected to be changed with time, i.e. convex movement during heating and concave one during cooling.

• 소성∙가공
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• 제22권1호
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• pp.11-16
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• 2013

Despite its importance the control of roller leveling has primarily relied on the operator's experience and on operation tables. In order to effectively eliminate various shape defects, the optimal leveling condition for a specific mode of plate deformation needs to be determined as well as a careful evaluation as to whether or not the condition is still appropriate for other modes or not. A numerical model, which considers both computation efficiency and accuracy, has been developed. The variations of residual stress are studied according to the entry and the delivery intermeshes, respectively. The camber deformation decreases linearly as the entry intermesh increases. In contrast the curl deformation does not vary directly with the entry intermesh. Therefore, the optimum intermesh values need to be determined in order to simultaneously minimize both the camber and the curl deformation.

• Journal of Power Electronics
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• 제9권6호
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• pp.960-968
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• 2009

This paper presents a design optimization process for interior permanent magnet synchronous motors (IPMSM) for hybrid electric compressors (HEC) which are applied to hybrid electrical vehicles. A hybrid electric compressor is composed of an electric motor driving section and an engine driving section which is connected to the engine by a pulley belt. A hybrid electric compressor driving motor requires half of the full driving power of a compressor. Even though an engine is not operated at the idling stop mode, the electric motor drives the air-conditioner compressor by itself so that the air conditioning system can produce its minimum cooling capacity. In this paper, the design optimization of an IPMSM for a 42 (V) applied voltage system is studied using the design of experiment (DOE) and response surface method (RSM) of 6sigma. The driving characteristics of this motor drive system are measured and analyzed by experiment.

• 대한기계학회논문집
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• 제17권10호
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• pp.2582-2589
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• 1993

Transient heat transfer characteristics of cooling of a spherical body were investigated in the radiatively active spherical medium. Initially the spherical body and the medium were maintained at their constant temperatures. Then heat transfer begins from spherical body t medium. The heat transfer mode inside the spherical body is just conduction. But heat is transferred by both conduction and radiation inside the medium. All thermodynamic properties were held constant in time. Spherical symmetry is assumed. DOM was adopted to solve RTE. The effect of characteries-tic optical thickness, conduction to radiation parameters, and solid surface emissivity has been studied.

• 태양에너지
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• 제4권2호
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• pp.43-49
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• 1984

Experiments were performed to study freezing on a finned vertical tube when either conduction in the solid or natural convection in a liquid controls the heat transfer. Conduction is the controlling mode when the liquid is at its fusion temperature, whereas natural convection controls when the liquid temperature is above the fusion value. The liquid was housed in a cylinderical containment vessel whose surface was maintained at a uniform, time-invariment temperature during a data run, and the freezing occurred on a finned vertical tube positioned along the axis of the vessel. The phase change medium was n-octacosan, a paraffin which freezes at about $61^{\circ}C$. For conduction-controlled freezing, the enhancement of the frozen mass due to finning is greatest when the frozen layer is thin and decrease as the layer grows thicker. The degree of enhancement is generally less than the surface area ratio of the finned and unfinned tube.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2000년도 특별강연 및 추계학술발표대회 개요집
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• pp.166-169
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• 2000

This paper presents a study on the LD Pump laser welded heat transfer and distortion analysis by using finite element method. In the production processing, ferrule and saddle of LD Pump in light-wave communication system are welded by multi mode Nd-YAG laser. Thus distortion happens during laser-welded packaging, and it makes an error of detecting the light signal translated through optical fiber in LD Pump. These parts experience thermal and mechanical hysteresis during heating and cooling process come from laser welding. The amount of final displacement is predicted using the finite element method. And the optimal shape is decided by using the result of pre-analysis.

• 한국세라믹학회지
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• 제34권5호
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• pp.461-466
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• 1997

Dielectric and piezoelectric properties of (Pb1-1.5xLnx)(Ti0.98Mn0.02)O3 ceramics with x=0~0.2 have been investigated. Pb(Ti0.98Mn0.02)O3 showed poor sinterability and cracking on cooling, but the substitution of Nd3+ ions into Pb2+ sites resulted in dense microstructures without cracking through reducing crystallographic anisotropy. The Nd3+ substitution, however, deteriorated the temperature stability of the piezoelectric properties because of lowering the Curie point. Electromechanical anisotropy(Kt/Kp) indicated a maximum value of 10 when x=0.1. This result might be attributed to the counteracting effects that with increasing x, the lattice anisotropy decreases while the poling becomes easier due to the increase in O2- vacancy concentration. Thickness-shear mode resonators with (Pb0.85Nd0.1)(Ti0.98Mn0.02)O3 composition showed good resonant characteristics around 4.5 MHz.