• Transactions of the Korean Society of Automotive Engineers
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• 제11권5호
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• pp.112-118
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• 2003

The friction coefficients of the rubber for clutch master cylinder were experimentally measured in this study. The cylindrical rubber samples for primary cup-seal and secondary cup-seal were tested against the aluminum or the steel plates of master cylinder housing under the various conditions of brake oil temperatures and normal loads. Dry sliding friction coefficients were also measured under various load conditions. The test revealed following results. First, the friction coefficient under fluid lubrication condition in general decreases, as the oil temperature or normal load increases. Second, the steel plate of low surface roughness yielded comparatively low friction coefficient on the range of 0.30∼0.67. On the other hand, the aluminum plate of high surface roughness yielded high friction coefficient on the range of 0.31∼1.15. Third, the friction coefficient of dry surface contact decreases as the normal load increases. This is contrary to the general principle of friction coefficient between metal plates.

• Wind and Structures
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• 제34권1호
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• pp.137-149
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• 2022

In this paper, the fluctuating lift and drag forces on 5:1 rectangular cylinders with two different geometric scales in three turbulent flow-fields are investigated. The study is particularly focused on understanding the influence of the ratio of turbulence integral length scale to structure characteristic dimension (the length scale ratio). The results show that both fluctuating lift and drag forces are influenced by the length scale ratio. For the model with the larger length scale ratio, the corresponding fluctuating force coefficient is larger, while the spanwise correlation is weaker. However, the degree of influence of the length scale ratio on the two fluctuating forces are different. Compared to the fluctuating drag, the fluctuating lift is more sensitive to the variation of the length scale ratio. It is also found through spectral analysis that for the fluctuating lift, the change of length scale ratio mainly leads to the variation in the low frequency part of the loading, while the fluctuating drag generally follows the quasi-steady theory in the low frequency, and the slope of the drag spectrum at high frequencies changes with the length scale ratio. Then based on the experimental data, two empirical formulas considering the influence of length scale ratio are proposed for determining the lift and drag aerodynamic admittances of a 5:1 rectangular cylinder. Furthermore, a simple relationship is established to correlate the turbulence parameter with the fluctuating force coefficient, which could be used to predict the fluctuating force on a 5:1 rectangular cylinder under different parameter conditions.

• Transactions of the Korean Society of Automotive Engineers
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• 제10권1호
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• pp.67-75
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• 2002

A study to investigate the influence of combustion chamber shape, especially piston top face configuration, on the combustion stability is presented with CFD analysis and single cylinder GDI engine test. Initial configuration of the piston bowl was designed with CFD analysis and further parametric studies of the design factors on the piston top face were carried out through the single cylinder GDI engine test. It was found that both the geometry of piston top face and the compression ratio have great influences on the combustion stability. Of interest is that the design factors of the GDI piston to prevent mixture diffusion out of the piston bowl have important roles for the stable combustion at the stratified mixture condition. Also the relationship between spray impingement and flow pattern in a GDI piston bowl should be considered to design an optimal bowl configuration for stable stratified combustion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.645-649
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• 1997

In case of swash plate type axial piston hydraulic motor, hydrostatic bearing used to achieve the lubrication effect on the mechanical sliding contact areas between the following parirs ; sliooer-pad and swash plate,piston and cylinder bore,valve plate and cylinder block, etc. This study discussed the basic charateristic for the hydrostatic slipper-pad bearings with the capillary or orifice restrictor under static load condition. And, we also development of hydrostatic bearing tester for hydrostatic balancing test of pistion & slipper-pad assembly, and some experimental data on supply pressure step responce are reported.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제24권6호
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• pp.880-885
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• 2000

Flow patterns and steady flow characteristics of an intake 3valve cylinder head are not obviously declared. Thus, in the study, the characteristics and limitation of intake flow coefficient which applied to multi intake valve engine are introduced. The flow coefficient and tumble characteristics are investigated by means of the steady flow test and flow visualization method. As the results, it is found that the intake flow rate is dominated by effective valve open area. In addition, this paper shows that the mass flow rate of intake 3valve engine is greater than that of intake 2valve engine and tumble flow of intake 3valve engine is superior to that of intake 2valve engine.

• Journal of Technologic Dentistry
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• 제23권1호
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• pp.115-121
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• 2001

This study was investigated on effect of implant system about investment condition and burn out temperature. Posterior bridges were fabricated by using plastic sleeve and gold sylinder. The results were as follows; In plastic sleeve test and fitting cast copings. the phosphate bonded investment showed better gypsum bonded investment. The pure special liquid showed better margin fitness compared with mixed liquid (special liquid + distilled water). In gold cylinder test. the good burn out temperature of Ceramic PFG and Crown Gold was evaluated $0^{\circ}C$ to $820^{\circ}C$ and was decreased on $780^{\circ}C$ for 30 minutes. $0^{\circ}C$ to $750^{\circ}C$ and was decreased on $650^{\circ}C$ for 30 minutes.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권1호
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• pp.1-13
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• 2014

A new 5-MW floating offshore wind turbine moored by a spring-tensioned-leg was proposed for installation in about 50m water depth. Its substructure is a platform of the inverted conical cylinder type with massive ballast weight plate at the bottom. A 1:128 scale model was built for the preliminary engineering development. The model tests in waves and wind were carried out to estimate motion characteristics of this platform in the Ocean Engineering Wide Tank of the University of Ulsan. Its motions were measured and the RAOs were compared. The proposed floating offshore wind turbine showed a good stability and decent responses in waves, wind and operation of the wind turbine.

• The KSFM Journal of Fluid Machinery
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• 제19권3호
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• pp.53-56
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• 2016

In this study, experiments and finite element method analysis were used to determine the autofrettage pressure that is optimal and then maximizes the cycling life of Type3 composite cylinders used in self-contained breathing apparatus. For both approaches, the cylinders were pressurized at 100, 110, ${\ldots}$, 290 % of the test pressure, respectively. The stresses were computed by the FEM analysis; while the strains of cylinders were recorded and the failure modes were monitored during the cycling test. As a result, from the good agreements between the simulations and experiments, it was concluded that at least 70 % of the test pressure should be applied as the autofrettage pressure in order to takes visible effect on the cycling life, and 160 % of the test pressure induces the maximum cycling life and the desired failure mode.

• Transactions of the Korean Society of Automotive Engineers
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• 제14권5호
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• pp.121-129
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• 2006

An Intake Port of SI engines plays a key role on improving engine performance by maximizing full load volumetric efficiency or by optimizing in-cylinder air motion. However, designing an intake port has been usually performed based on port experts' experience and know-how, which means that analytical analyses are relatively insufficient. In this paper, port design parameters which decide an overall port shape were defined in order to correlate them relevantly with flow test results accumulated so far. Test species were composed of all twenty eight SI engines which cover major engine displacements from 1,000cc to 4,000cc. First, they were tested on a steady state flow test rig to find out their flow coefficients. Secondly, those flow coefficients were analyzed based on the port design parameters measured from the engines. The most effective parameters were port height, valve head diameter, and the ratio of port size and cylinder bore diameter. The final correlation equation could predict flow coefficients within 2% deviation.

• Journal of the Korean Recycled Construction Resources Institute
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• 제4권1호
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• pp.38-46
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• 2016

In this study, the bleeding tests were performed to investigate the effects of cement paste(w/c=0.42) on bleeding through varying the number of strand and the diameter of cylinder. The test variables were specified by differing the diameter of cylinder and the number of strand. The bleeding test was performed with respect to all diameter parameters by with or without strand. In addition, the number of strands were specified at four levels, 0, 1, 2, and 3 EA in case of 50 mm cylinder. In case of without strand, the bleeding rate was determined at low level under 2%. Moreover, all of the specimens had similar value in the measurement error. In case of with strand, maximum bleeding rate was 10%. As the diameter of cylinder decreased, the bleeding rate was decreased. The bleeding rate was altered rapidly in between 50 to 100mm of diameter. Even though bleeding rate was increased according to the increase in the number of strand, these tendency for bleeding rate was negligible with the measurement error.