• Journal of the Korean Society for Precision Engineering
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• v.22 no.1
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• pp.137-142
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• 2005

Gas-Assisted Injection Molding(GAIM) is an innovative technology for producing plastic parts and has been received extensive attention in the plastic manufacturing industries. But, due to gas-polymer interacting during the gas injection phase, the process has significantly different characteristics from conventional injection molding and, therefore, the control of the process requires much technical knowledge in processing and materials. The experiment was performed about variations of gas-penetration length that is affected by filling imbalance resulting from the structure of runner. The Taguchi method was used for the design of experiment. The most effective factors for the gas-penetration length were the shot size and mold temperature. The most effective factors for the difference of the gas-penetration length were the melt temperature and shot size. This study also discussed the filling imbalance phenomenon in a unary branch runner type mold that has geometrically balanced runner.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1171-1177
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• 2010

This paper presents a robust design procedure for minimizing warpage in plastic injection-molded products, where the Pick-the-Winner rule based on Taguchi's Orthogonal Array experiments and the Design Space Reduction Method are integrated for optimization. Two-step optimization approach is applied to reduce warpage in the part design stage and additionally to minimize the warpage in the process conditions design stage. Taguchi's S/N ratio is introduced as a design metric to evaluate robustness against process variations. The effectiveness of proposed optimization process is shown with an example of warpage minimization problem.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.258-265
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• 2001

Turbine blade is subject to force of three type ; torsional force by torsion-mount, centrifugal force by rotation of rotor and cyclic bending force by steam pressure. Cyclic bending force of them is main factor on fatigue fracture. In the X-ray diffraction method, the change in the values related to plastic deformation and residual stress near the fracture surface mat be determined, and information of internal structure of material can be obtained. Therefore, to find a fracture mechanism of torsion-mounted blade in nuclear plant, based on the information from the fracture surface obtained by fatigue test, the correlation of X-ray parameter and fracture mechanics parameter was determined, and then the load applied to actual broken turbine blade parts was predicted. Failure analysis is performed by finite element method and Goodman diagram on torsion-mounted blade.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.86-93
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• 2013

Main function of the Press forming Machine is the forming for plates. The head of the Press forming machine consist of several parts. It was named Press forming-contraction and Press forming_expansion according to formability of plates. Aluminium and Titanum plates are forming by using the Press forming machine. In this study, we analyzed sheet metal forming including plastic deformation and the contact pressure in the bearing. Finite element analysis results of Press forming-contraction and Press forming_expansion show the similar results of the actual specimen plates and the bearing contact pressures show the acceptable level of stress in both aluminum and titanium specimens.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.345-349
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• 2014

In this study, an age-hardened 6061-T6 alloy sheet was used, which is commonly utilized for auto parts. The junction strength characteristics in relation to the stirring speed and welding speed were studied in accordance with the friction stir welding rotation of the tool pin. Micro hardness measurements of A type and B type pins, for a welding speed of 400 mm/min and a tool rotational speed 3000 rpm, were obtained as Hv104 and Hv111, respectively. For a welding speed of 200 mm/min and a tool rotational speed of 2000 rpm, we obtained Hv48 and Hv50 for A and B type pins, respectively. Microstructure observation showed that the stirring portion was fine and uniform, which occurred because of its plastic deformation. In the thermomechanically affected zone, partial recrystallization was present because of the plastic deformation. The crystal grains in the heat affected zone were coarsened due to the heat generated by friction stir welding.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.53-62
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• 2004

A single layer latticed dome is one of the most efficient structures because of its low specivic gravity. For easily analyzing of a single layer latticed dome, joint system is assumed to be pin or rigid joint. However, its joint uses ball whose system has intermediate properties of pin and rigid joint. Therefore this study has a grasp of bending rigidity, stress and mechanical properties through experimental and analyzing method of the bolt inserted ball joint. To analyze the stress of bolt and sleeve, this study uses through 3D elastic contact and cubic element, and then the ball and the bolt are perfectly connected for easily analyzing Compared experimental results to F.E.M, each specimen has an error of less than 12 percent. In the results of stress distribution through F.E.M, stress occurs from bottom of bolt to top of sleeve, and most of tension appears on the bolt, also compression occurs from upper parts of the bolt to the sleeve. The assumption of bending stiffness in ball joint is well known that bolt resists only tension and upper sleeve resiss compression. The results of experiment and analysis have $7{\sim}56%$ error, assuring that upper part of bolt occurs of partial compression. In the result of modified assumption have $4{\sim}20%$ error.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.284-291
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• 2005

A RC column-bent pier represents one of the most popular piers used in highway bridges. Seismic performance of reinforced concrete (RC) column-bent piers under bidirectional seismic loadings was experimentally investigated. Six column bent-piers were constructed with two circular supporting columns which were made in 400mm diameter and 2,000mm height. Test parameters are different transverse reinforcement and loading pattern. These piers were tested under lateral load reversals with the axial load of $0.1f_{ck}A_g$. Three specimens were subjected to bidirectional lateral load cycles which consisted of two main longitudinal loads and two sub transverse loads in one load cycle. Other three specimens were loaded in the opposite way. Test results indicated that lateral strength and ductility of the latter three specimens were generally bigger than those of the former three specimens. Plastic hinges were formed with the spall of cover concrete and the fracture of the longitudinal reinforcing steels in the bottom plastic hinge of two supporting columns for the former three specimens. Similar behavior was observed in the top and bottom parts of two supporting columns for the latter three specimens.

• Steel and Composite Structures
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• v.26 no.5
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• pp.621-634
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• 2018

Flush end-plate (FEP) beam-to-column joints are commonly used for gravity load resisting parts in steel multi-storey buildings. However, in seismic resisting structures FEP joints should also provide rotation capacity consistent with the global structural displacements. The current version of EN1993-1-8 recommends a criterion aiming at controlling the thickness of the end-plate in order to avoid brittle failure of the connection, which has been developed for monotonic loading conditions assuming elastic-perfectly plastic behaviour of the connection's components in line with the theory of the component method. Hence, contrary to the design philosophy of the hierarchy of resistances implemented in EN1998-1, the over strength and the hardening of the plastic components are not directly accounted for. In light of these considerations, this paper describes and discusses the results obtained from parametric finite element simulations aiming at investigating the moment-rotation response of FEP joints under cyclic actions. The influence of bolt diameter, thickness of end-plate, number of bolt rows and shape of beam profile on the joint response is discussed and design requirements are proposed to enhance the ductility of the joints.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.218-223
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• 2000

The shot peening is largely used for a surface treatment in which small spherical parts called shots are blasted on a surface of a metallic components with velocities up to 100m/s. This treatment leads to an improvement of fatigue behavior due to the developed compressive residual stresses, and so it has gained widespread acceptance in the automobile and aerospace industries. The residual stress profile on surface layer depends on the parameters of shot peening, which are, shot velocity, shot diameter, coverage, impact angle, material properties etc. and the method to confirm this profile is only measurement by X-ray diffractometer. Despite its importance to automobile and aerospace industries, little attention has been devoted to the accurate modelling of the process. In this paper, the simulation technique is applied to predict the magnitude and distribution of the residual stress and plastic deformation caused by shot peening with the help of the finite element analysis.

• Korean Journal of Human Ecology
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• v.18 no.2
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• pp.397-406
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• 2009

A Study on the Development of Brassiere Pattern for Elderly Women The purpose of this study is to develop functional and sensible brassiere for elderly women. For this purpose, 6 elderly women(aged between 65 and 69) were sampled to be measured for their body sizes and tested for their bressiere wearing. he results were as follows; 1. In order to develop the basic patterns of elderly women's bressieres, 90B size was selected and then, their bressiere fitting was tested. The foundation pattern of the size 90A was proved for the body by the wearing tests. Each angle and length of the parts on the basic line of the breasts played an important role on setting the pattern. 2. As based on the body surface shell extracted from a plastic mold(photo.2), the cup of brassiere pattern were applied to the body surface shell(photo.4), and full side stretch-wings were applied to 13% reduced body size. The design pattern of elderly women's brassiers were characterized by a round wired as well as a full cup(3piece) embracing the entire breasts. 3. As the result of the wearing test, the excellence of the experimental brassiere was recognized objectively, with high marks in all the items(fig. 6). The experimental brassiere was covering the whole breasts to cope with change according to breasts loosing. It was designed to support the breasts firmly.