• 대한기계학회논문집B
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• 제26권1호
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• pp.1-11
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• 2002

Flow of fluid has been studied in various fields of fluid engineering. To hydraulic engineers, the unsteady flow such as pulsation and liquid hammering in pipes has been considered as a serious trouble. So we are supposed to approach the formalized mathematical model by using more exact momentum equation for fluid transmission lines. Most of recent studies fur pipe line have been studied without considerations of variation of viscosity and temperature, which are the main factors of pressure loss causing the friction of fluid inside pipe line. Frequency response experiments are carried out with use of a rotary sinusoidal flow generator to investigate wave equation take into account viscosity and temperature. But we observed that measured value of gains are reduced as temperature increased. And it was respectively observed that the measured value of gains are reduced and line width of gain is broadened out, when temperature was high in the same condition. As we confessed, pressure loss and phase delay are closely related with the length, diameter and temperature of pipe line. In addition, they are the most important factors, when we decide the momentum energy of working fluid.

• Geomechanics and Engineering
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• 제38권3호
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• pp.261-273
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• 2024

This study presents a groundbreaking analytical approach to find an exact solution for the bearing capacity of strip footings on reinforced slopes, utilizing the two-phase approach and slip line method. The two-phase approach is considered as a generalized homogenization technique. The slip line method is leveraged to derive the stress field as a lower bound solution and the velocity field as an upper bound solution, thereby facilitating the attainment of an exact solution. The key finding points out the variation of the bearing capacity factor N_γ with influencing factors including the backfill soil friction angle, the footing setback distance from the slope crest edge, slope angle, strength, and volumetric fraction of inclusion layers. The results are evaluated by comparing them with those of relevant studies in the literature considering analytical and experimental studies. Through the application of the two-phase approach, it becomes feasible to determine the tensile loads mobilized along the inclusion layers associated with the failure zone. It is attempted to demonstrate the results by utilizing non-dimensional graphs to clearly illustrate variable impacts on reinforced soil stability. This research contributes significantly to advancing geotechnical engineering practices, specifically in the realm of static design considerations for reinforced soil structures.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.580-585
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• 2003

Korean high speed train (KHST) has adopted a combined electric/ mechanic (friction) braking system. Electric brakes are consist of rheostatic brake, regenerative brake and eddy current brake and mechanical brakes are composed of disc brake, wheel disc brake and tread brake. In this paper, we introduce the braking performance test and the measuring method of mechanical brake. And disc brake performance has been reviewed by the experimental method. The on-line test of KHST has been carried out up to 260 km/h and proved that the disc braking capacity of KHST is sufficient.

• Journal of Mechanical Science and Technology
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• 제20권12호
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• pp.2242-2249
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• 2006

The rolling piston type rotary compressor has been widely used for refrigeration and air-conditioning systems due to its compactness and high-speed operation. The present analysis is part of a research program directed toward maximizing the advantages of refrigerant compressors. The study of lubrication characteristics in the critical sliding component is essential for the design of refrigerant compressors. Therefore, theoretical investigation of the lubrication characteristics of a rotary compressor being used for refrigeration and air-conditioning systems was investigated. The Newton-Raphson method was used for a partial elastohydrodynamic lubrication analysis between the vane and the rolling piston of a rotary compressor. The results demonstrated that the vane thickness and the center line position of the vane significantly influenced the friction force and the energy loss between the vane and the rolling piston.

• Nuclear Engineering and Technology
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• 제29권2호
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• pp.158-166
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• 1997

Integrated performance test of Chemical and Volume Control System was successfully performed in 1994. However, an extensive effort to correct hardware and software problems in the letdown line was required mainly due to the lack of adequate simulation code to predict the test accurately. Although the LTC computer code was used during the YGN 3'||'&'||'4 NSSS design process, the code can not satisfactorily predict the test due to it insufficient letdown line modeling. This study developed a numerical model to simulate the letdown test by modifying the current LTC code, and then verified the model by comparing with the test data. The comparison shows that the modified LTC computer code can predict the transient behavior of letdown system lese very well. Especially, the model was verified to be able to predict the "Stiction (composition of stick and friction)" phenomena which caused instantaneous fluctuations in the letdown backpressure and flowrate. Therefore, it is concluded that the modified LTC computer code with the ability of calculating the "Stiction" phenomena will be very useful for future plant design and test predictions.predictions.

• 소성∙가공
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• 제7권4호
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• pp.354-363
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• 1998

In order to analyze the stretch forming characteristics of tailored blanks, laser welded blanks of different thickness and strength combinations were prepared and stretching tests were done. The stretching formability of laser welded blanks was reduced as increasing the deformation restraining force ($strength{\times}thickness$) ratio between two welded sheets. Weld line movement was attributed to strain concentration at weaker sheets and resulted in fracture at weaker sid, so that fracture could be predicted by the forming limit of the weak sheet. In the case of a welded blank with the similar deformation restraining force rations between two welded sheets, crack occurred at weld and its forming limit was about 15% less than the base sheet. The effects of lubrication and weld line position on stretch-ing formability were also investigated by experiments. Lower friction did not always give better formability for tailored blanks. Stretching formability was observed to be improved as increasing the area of weak sheet.

• 한국해양공학회지
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• 제12권3호통권29호
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• pp.75-85
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• 1998

A finite difference model for predicting time-dependent, wave-induced nearshore current is studied. The model includes wave refraction, wave-current interaction, bottom friction and wind effect. This model iteratively solved the linear the linear set of conservation of both mass and momentum, which were time averaged (over one wave period) and depth integrated, for mean velocities and free surface displacement. Numerical simulations of nearshore current under oblique wave attack, and for wave and wind induced current on a longshore periodic beach are carried out. Longshore velocities tend to zero in some distances outside the breaker line. And the peak velocity is shifted shoreward at the breaker line. The results represent the general characteristics of the nearshore current induced by wave.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.136-139
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• 1997

Applications of commercial software DEFORM-3DTM for 3-D simulation in extrusion process are developed for the analysis of twisting of extruded products. Because the elliptical shape has at least one line symmetry, the twisting is not occured during the extrusion. But, the results of extrusion simulation of the elliptical shape show that the twisted boundary of the die surface makes the material inside die surface rotate with the constant angular velocity. Otherwise, the simulation results of the S shaped product show that the twisting can be occured by the only 180$^{\circ}$rotation symmetry of S shape without no line symmetry and show that the angular velocity increases by the only 180$^{\circ}$rotation symmetry without no twisted die surface between on the die entrance section and on the die exit section. The results of the analysis show that the angular velocity of the extruded product changes with die length and friction condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1782-1784
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• 2002

In this paper, the coefficient of friction betwee and sheath in 345kv XLPE cable was measured the simulated inclinated condition of You-Youngdeungpo transmission line. The phenomena of slipping down the simu inclination was investigated theoretically usin measured data and was analyzed from experim result. The measured and analyzed result were conside be as a reference data for real installation of XLPE Youngseo-Youngdeungpo transmission line.

• 한국표면공학회지
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• 제23권1호
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• pp.1-7
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• 1990

Ion implantation is a well established superior superior surface modification technique for the improvement of wear resistance, hardenece, hardness, corrosion resistance, biocompaibity, surface friction, as well as for the modification of surface electric conductance. Conventional ion implantaion is a line-of-sight process witch ues the ion beam accelerator techniques. Plasma sheath ion implantation (PSII), as a new technique, is described in this paper. In PSII high voltage pulse is applied to a target material placed directly in a plasma, forming a think ion-matrix sheath around the target. Ions accelerate through the sheath drop and bombard the traget from all sides simultaneosuslyregardless of the target shape. This paper describes the principle of PSII, which has non-line-of sight characteristics, as well as the experimental appratus.