• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.83-86
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• 2008

In this study, friction test was proposed to obtain coefficient of friction between tube and die in guide zone of tube hydroforming and friction coefficients were evaluated at different materials, viscosity of lubricants and internal pressures. For this study, STKM11A and SUS tubes were prepared. The tube was expanded by an internal pressure against the tool wall. By pushing the tube through the tool, a friction force at the contact surface between the tube and the tool occurs From the recorded axial feeding forces, the friction coefficients between tube and die at the guide zone in tubular hydroforming can be estimated. The effects of the various internal pressures, viscosity of lubricants, tube materials, tube size and die coating on the friction forces and friction coefficients are discussed.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1564-1568
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• 2004

The requirements of internal balance were studied that should be considered on performing force & moment transonic wind tunnel testing to develop combat aircraft. In many insecure factors of test condition, uncertainty analysis was conducted to verify one drag count measurements. The analysis result was applied to T-50 aircraft model and compared for data verifaction. In conclusion, the aerodynamicist should estimate the validation and accuracy of test data by having an overall grasp of system components including internal balance. It will help him get high productivity of testing and effective validated data at tunnel.

• Korea-Australia Rheology Journal
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• v.16 no.3
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• pp.153-160
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• 2004

Open microcellular foams having small-sized cell and good mechanical properties are desirable for many practical applications. As an effort to reduce the cell size, the microcellular foams combining viscosity improvers into the conventional formulation of styrene and water system were prepared via high internal phase emulsion polymerization. Since the material properties of foam are closely related to the solution properties of emulsion state before polymerization, the flow behavior of emulsions was investigated using a controlled stress rheometer. The yield stress and the storage modulus increased as viscosity improver concentration and agitation speed increased, due to the reduced cell size reflecting both a competition between the continuous phase viscosity and the viscosity ratio and an increase of shear force. Appreciable tendency was found between the rheological data of emulsions and the cell sizes of polymerized foams. Cell size reduction with the concentration of viscosity improver could be explained by the relation between capillary number and viscosity ratio. A correlative study for the cell size reduction with agitation speed was also attempted and the result was in a good accordance with the hydrodynamic theory.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.4
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• pp.367-371
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• 2003

In order to determine the effective way of measuring the Mode I stress intensity factor for a material containing a two-dimensional surface crack by means of the alternating current potential drop(ACPD) technique, the change in magnetic flux density between crack surfaces and above the specimen surface due to load was studied theoretically. The magnetic flux density in the air between crack surfaces is uniform and above the specimen surface is not changed by increasing the load in the material. Therefore, the change in potential drop due to load in a measuring system which was designed to induce a large amount of electro-motive force was caused by the change in internal inductance of material, the change in the mutual inductance between internal inductance of material and measuring system and the change in the mutual inductance between internal inductance of material and power supply line.

• Earthquakes and Structures
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• v.15 no.4
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• pp.361-367
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• 2018

In this paper, dynamic analysis of concrete pipe submerged in the fluid and conveying fluid is studied subjected to earthquake load. The structure is modeled by classical shell theory and the force induced by internal fluid is obtained by Navier-Stokes equation. Applying energy method and Hamilton's principle, the motion equations are derived. Based on Navier and Newmark methods, the dynamic deflection of the structure is calculated. The effects of different parameters such as mode number, thickness to radius ratios, length to radius ratios, internal and external fluid are discussed on the seismic response of the structure. The results show that considering internal and external fluid, the dynamic deflection increases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.9-12
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• 2000

Insulators for high-voltage and large-power should be endured mechanically the weight of mold bushing itself and the force of pushed from contact with circuit breaker and conductor. But dielectric breakdown could be occurred result from the external circumstances and internal factors such as chemical reaction, partial discharge, change of temperature and the relation of temperature-time in process of casting. Therefore, to get rid of external and internal factors of dielectric breakdown. Furthermore, to prevent the internal cracks, void, cavity which resulted from the contraction originated on the interface between copper and epoxy resin, formed semi-conductive layer with partially carbon painted on copper bar. The PD properties and the insulation qualities of epoxy molded insulators were improved by roles of cushions for the direction of diameter and natural sliding effects as like separated from conductor for the direction of length.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.21-24
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• 1994

A piezoelectric actuator. which is composed of a piezoelectrically driven stator and a rotor, Is made and the characteristics are investigated experimentally is a new ultrasonic actuator which transforms rotary motion to linear one is proposed and proved to work successfully. If an ultrasonic wave is excited to propagate in the stator, particles on the internal surface move elliptically. Since the internal surface is machined as an internal thread and an external thread(rotor) is put into the stator. the external thread is rotated through the friction force and moved in the axial direction. The traveling wave is excited by a piezoelectric element bonded to the stator. This idea is firstly proposed by S. Ueha, et al. in 1987. However, efficiency of their actuator is less than 3%. In this study, in order to improve characteristics of this type actuator, we used various pitches and number of the screw thread, and materials of rotor, and we obtained good charcteristics.

• Tribology and Lubricants
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• v.24 no.5
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• pp.215-220
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• 2008

An internal friction model was developed to model the frictional behavior of automotive Constant Velocity (CV) joints by using the test data from an instrumented CV joint friction apparatus with actual driveshaft assemblies. Experiments were conduced under different realistic operating conditions of oscillatory speeds, CV joint articulation angles, lubrication, and torque. The experimental data were used to develop a physics-based semi-empirical CV joint internal friction coefficient model as a function of different CV Joint operating parameters. It was found that the proposed friction model captures the experimental results well not only the static behavior of friction coefficient, but also the dynamic friction terms, which is the main source of force that causes vehicle vibration problems.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.2
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• pp.83-90
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• 2005

A mirror cam mechanism a kind of conjugate cam mechanism consists of two cams, two rollers, and two links. Since profiles of two mirror cam are identical, a simultaneous machining of two cams is achievable. Some machining errors on cam profiles do not result in the internal acting force, which often causes problems in high speed cam mechanism between two links. Also, since angular accelerations of two links are same, the internal acting force by the difference of the angular accelerations does not occur in the mechanism. Thus the mirror cam mechanism is very useful in high speed machinery. This paper studies a design method as well as a machining method, and develops an exclusive CAD/CAM software for mirror cam profiles. The developed CAD/CAM software is applied to a typical mirror cam mechanism and a mock-up equipment is built in order to test the machinism mirror cm. Experimental investigations show that the contact between cam surface and roller surface according to cam rotation agrees well with the simulation on the developed CAD/CAM software.

• The Journal of Internal Korean Medicine
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• v.17 no.1
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• pp.175-192
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• 1996

These studies were carried out to investigate the effect of Jungchuntang water extract on the inhibitory contractile action of acetylcholine in rat. The results of these studies were as follows; 1. Contractile force of acetylcholine from trachea smooth muscle in rat was significantly inhibited by Jungchuntang. 2. Dose-response of acetylcholine pretreated Jungchuntang in rat was not significantly changed. 3. Inhibitory contractile action of acetylcholine pretreated propranolol in rat was decreased. 4. Inhibitory contractile action of acetylcholine pretreated indomethacin was not significantly changed by Jungchuntang. 5. Inhibitory contractile action of acetylcholine pretreated methylene blue was significantly changed by Jungchuntang. 6. Contractile force of acetylcholine from trachea smooth muscle in rat was significantly inhibited by Jungchuntang. 7. Dose-response of acetylcholine pretreated Jungchuntang in rat was not significantly changed. 8. Inhibitory contractile action of acetylcholine pretreated propranolol in rat was decreased. 9. Inhibitory contractile action of acetylcholine pretreated indomethacin was not significantly changed by Jungchuntang. 10. Inhibitory contractile action of acetylcholine pretreated methylene blue was significantly changed by Jungchuntang.