• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.2945-2951
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• 2000

Because of the inherent flexibility in their design for improved material properties, composites have wide applications in aerospace vehicles and automobiles. The purpose of this study is to investigate the energy absorption characteristics of CFRP( Carbon Fiber Reinforced Plastics); tubes on static and impact tests. Static compression tests have been carried out using the static testing machine(Shin-gang buckling testing machine)and impact compression tests have been carried out using the vertival crushing testing machine. When such tubes were subjected to crushing loads, the response is complex and depends on the interaction between the different mechanisms that control the crushing process. The collapse characteristics and energy absorption were examined. Trigger and interlaminar number affect energy absorption capability of CFRP tubes.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.76-81
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• 2003

The purpose of this study is to analyze the collapse characteristics of widely used spot welded section members coated damping material Y1000 and to develop an analysis method for acquiring exact collapse loads and energy absorption ratio. Hat-shaped thin-walled members have the biggest energy absorbing capacity in a front-end collision. The sections were tested on quasi-static and impact loads. Specimens with two type thickness, width ratio and spot weld pitch on the flange have been tested in impact velocities(6.73n0sec and 7.54n1sec) which imitate a real-life car collision. As a result, it was developed the system for acquiring impact energy absorbing characteristics of structure united thin-walled member and damping materials.

• Journal of Biomedical Engineering Research
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• v.22 no.1
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• pp.29-34
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• 2001

본 연구의 목적은 대퇴부가 절단된 다리의 생체 역학적 기능을 복구할 수 있게 하는 의지의 개발을 위하여 5축 링크, 슬관절 완충장치를 사용하여 보행시 입각기를 제어할 수 있는 대퇴 의지 시스템 개발에 있다. 이를 위하여 입각기시 대퇴의지와 지면간 접촉 중 충격 에너지 흡수를 하는 슬관절 완충장치의 기계적 특성 및 거동을 분석하였다. 임상시험을 통하여 개발된 대퇴의지의 성능을 검증한 결과 대퇴 절단 피검자들의 보행특성은 정상인의 보행에 근접한 경향을 보였다. 결론적으로 본 연구에서 개발된 입각기 대퇴의지는 입각기시 현저한 보행 안전성을 보였다.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.9
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• pp.1661-1668
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• 2001

본고는 지뢰 방호복을 개발, 국산화하기 위해 먼저 방탄소재 구성방법에 관하여 실험한 결과이다. 기존의 여러 겹의 파라-아라미드(Para-aramid)나 단순히 파라-아라미드와 폴리 에틸렌 필름(Polyethlene film)을 조합한 소재구성과는 달리 케블라 파이버(Kevlar fiber)로 만들어진 펠트(felt)를 첨가하여 방탄원리 및 특성을 고려한 구성으로 방호복의 중량을 줄이면서 착용자로 하여금 유연성과 동작성을 향상시켜 임무수행과 안전성을 높일 수 있는 방호복을 개발하고자 하였다. 1) Para-aramid(내 충격열) + Flex-felt(충격 에너지 흡수) + Para-aramid(backface Polyethylene film(에너지 분산 극대)+Para-aramid(내 마찰열, backface순으로 소재를 배열함으로써 기존의 Para-aramed 36겹에 대하여 Para-aramid13겹, Polyethylene film 13겹, 그리고 펠트 1겹으로 동일한 방호성능을 얻었다. 2) 새로운 소재 구성 방법 에 의 한 방탄소재는 동일한 방호성능을 갖는 기존의 소재 구성 방법 에 따른 방탄소재 보다 중량에서 34-l9% ,더 가벼운 것으로 나타나 방호복 구성시 유연성이나 동작성에 유리 할 것으로 사료된다. 3) NIJ-STD-0101.03에서 의 Armor type II에 해당하는 시편 I의 방호한계속도로 구한 운동 에너지량은 154.4J Armor type III-A에 해 당하는 시편II의 방호한계속도로 구한 운동 에너지 량은 183.0J로 나타나 두 시편 모두 5m의 거리에서 M16Al지뢰의 0.032~0.044g사이 의 파편에 대해서 50%의 관통확률을 갖는 것으로 나타났다.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.17-22
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• 2003

This paper presents an experimental investigation of a reversible colloidal seismic damper, which is statically loaded, The porous matrix is composed from silica gel (labyrinth or central-cavity architecture), coated by organo-silicones substances, in order to achieve a hydrophobic surface. Water is considered as associated lyophobic liquid. Reversible colloidal damper static test rig and the measuring technique of the static hysteresis are described. Influence of the pare and particle diameters, particle architecture and length of the grafted molecule upon the reversible colloidal damper hysteresis is investigated, for distinctive types and mixtures of porous matrices, Variation of the reversible colloidal damper dissipated energy and efficiency with temperature, pressure, is illustrated.

• Journal of the Korean Institute of Gas
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• v.13 no.4
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• pp.27-32
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• 2009

This paper presents the stress and deformation behaviors using the finite element method as a function of the thickness of the helmets without the bead frames on the top of the shell structure. The helmet that would provide head and neck protections without causing discomfort to the user when it was worn for long periods of time should be manufactured for increasing the safety and impact energy absorption. The FEM computed results show that when the impulsive force is applied on the top surface of a helmet, the maximum stress and strain have been occurred around the position of an applied impact force, which may lead to the initial failure on the top surface of the helmet shell. As the helmet thickness is decreased from 4mm to 2mm, the impact energy absorbing rate is radically increased, and the maximum stress of the helmet is increased over the tensile strength, 54.3MPa of the thermoplastic material. Thus, the top surface of the helmet should be supported by a bead frame and increased thickness of the shell structure.

• Composites Research
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• v.15 no.1
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• pp.32-40
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• 2002

This study developed fabrication process of $SiC_p/Al$ metal matrix composites as electronic packaging materials by squeeze casting method. The $SiC_p$ preform were fabricated in newly designed preform mold using about 0.8 % of inorganic binder(SiO$_2$) and 5 vol.% of $Al_2O_3$fiber. To infiltrate the molten metal into the preform, fabrication condition such as the temperature and the pressure were selected. Applying the fabrication conditions, heat transfer analysis were preformed using finite element method and thus analyzed the temperature distribution and cooling characteristic during the squeeze casting. For the fabricated composites, impact toughness and thermal expansion coefficient were measured. The metal matrix composites developed in this study have 0.2~0.3 J impact toughness, $8~10 ppm/^{\circ}C$ thermal expansion coefficient and $2.9~3.0g/cm^3$density which is appropriate properties for electronic packaging application.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.10
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• pp.80-87
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• 2006

Metallic sandwich plate with a truss core has metallic inner structures which have low relative density between a pair of metal skin sheets or face sheets. In this work, low impact tests have been carried out to examine the behavior of sandwich plates with a pyramidal truss core. For the low velocity impact, the impact apparatus of drop weight type has been fabricated. From the results of the experiments, maximum energy absorption is found to happen when the upper sheet fails. The sandwich plate loses its absorption ability as soon as the inner structures have been crashed completely and optimal core thickness has existed to maximize energy absorption. Comparing the metallic sandwich plate with the monocoque plate, the absorbed energy has been improved up to 160 % and the deflection decreased by up to 76%. As a result, the metallic sandwich plate with a truss core is shown to have good material for impact resistance and energy absorption.

• Korean Journal of Materials Research
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• v.7 no.7
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• pp.623-631
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• 1997

본 연구에서는 주조 2상 스테인리스강의열시효에 대한 시효온도, 시효시간 및 Nb함유량의 영향을 관찰하기 위해 기계적 성질 및 조직을 조사하였으며 Nb을 함유한 주조 2상 스테인리스강의 파괴기구를 규명하기 위해 SEM에 의한 파단면 관찰과 WDS성분분석을 통해 파괴기구의 특성을 고찰하였다. 시효온도와 시효시간이 증가함에 따라 페라니트으 미소경도가 증가하였으며 항복강도의 경우 시효온도와 시효시간에는 영향을 받지 않았으나 Nb을 함유한 재료들이 Nb을 함유치 않은 재료들에 비해 다소 낮은 항복강도 값을 보였다. 충격흡수에너지 값은 시효시간 및 시효온도의 증가에 따라 시험된 모든 재료에서 저하되었는데 0.4% Nb을 함유하는 경우 Nb을 약간 함유하거나 함유치 않은 재료들에 비해 시효시간에 따라 급격한 감소 경향을 보였다. 파단면 관찰결과 페라이트 기지 또는 페라이트/오스테나이트 상경계에서 석출된 VbC를 비롯한 탄화물들이 취성저항성을 낮추는데 크게 기여했음을 알 수 있었다.

• Journal of Korean Society of Steel Construction
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• v.24 no.6
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• pp.693-700
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• 2012

In this study, the Charpy impact test along with metallurgical observation was conducted to evaluate low temperature impact toughness of structural steel welds with different welding processes to find out the optimal welding process to guarantee the required impact toughness at low temperatures. The welding processes employed are shield metal arc welding (SMAW) and flux cored arc welding(FCAW), which are commonly used welding methods in construction. The Charpy impact test is a commercial quality control test for steels and other alloys used in the construction of metallic structures. The test allows the material properties for service conditions to be determined experimentally in a simple manner with a very low cost. To investigate the impact toughness at low temperatures of the steel welds, specimens were extracted from the weld metal and the heat affected zone. Standard V-notch Charpy specimens were prepared and tested under dynamic loading condition. The low temperature impact performance was evaluated based on the correlation between the absorbed energy and the microstructure. Analysis of the results showed that the optimal welding process to ensure the higher low temperature impact toughness of the HAZ and the weld metal is SMAW process using the welding consumable for steels targeted to low temperature use.