• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.378-378
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• 2002

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.92-97
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• 2000

Low-velocity impact damage of a thick pressure vessel by composite materials was studied using the modified Herzian contact radius theory. Impactors of various masses and various tup shapes were dropped freely in the range of 20m to 200mm height. With acceleration gage and strain gage installed on the impactor, impact force and acceleration and Contact radius were measured. After a test, the samples were radiographed to scan the state of damage. Compared with hemispherical tup of 12.7mm diameter, the contact radius of hemispherical tup of 25.4mm diameter was bigger. And the experimental data and the theoretical data was different due to the mechanical properties difference. The acceleration value was changed linearly according to the height.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.639-644
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• 2015

A cylindrical secondary Li-ion cell is a device in which stored chemical energy is converted to electrical energy via an electrochemical reaction. These cells are widely used for applications that require high capacity and rate power, such as notebooks, power tools, and electric vehicles. The role of a center pin is to retain the channel for gas release, preventing blockage of the hollow of the jelly roll during a charge-discharge cycle, and to prevent an internal short circuit for tearing of separator under mechanical free fall. In this paper, two experiments are conducted with and without the center pin to experimentally verify the importance of the role of the center pin. The first experiment is a 50-cycle charge-discharge cycle test, and the second is a free fall test conducted according to the Underwriters Laboratories (UL) standards. Based on these experiments, we demonstrate that the center pin in a cylindrical cell is a very important component in terms of safety.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.745-748
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• 2002

Many malfunctions take place in container crane spreader due to impact. So we designed a 2DOF hydraulic impact absorbing system and studied the change of impulse with respect to the variation of falling height and weight. The falling height becomes higher than 1m and the falling weight goes up heavier than 100kg, the impact absorbing rate was lower. When spreader is bumped against container and impulse force concentrates on one point, impact absorbing equipment would not be operated properly and make some trouble.

• Composites Research
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• v.26 no.3
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• pp.195-200
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• 2013

This study aims to detecting and analyzing the defects of damaged carbon fiber reinforced composites after impacts, particularly focusing on barely visible impact damages. The impact test was progressed by a drop-weight machine and applied to introduce simulated damages on laminated composites used in aircrafts. Various nondestructive testing (NDT) techniques were applied to identify the defects on the specimens with different levels of impact energies. Based on the measurements data, the levels of the barely visible impacts, and the applicability and effectiveness of the detection methods were discussed. Generally, the results demonstrated that their inner damages contained bigger footprints than those on the surfaces. However, when the damage energy was low, it was found that the inner damage size could be smaller than those appeared on the surfaces.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.25-25
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• 1998

진동시험기를 사용한 충격시험은 자유 낙하식 충격시험기를 이용하는 것 보다 여러 가지 장점이 있으며, 충격반응 스펙트럼 시험의 요구가 점점 증가하고 있다. 진동시험기를 이용하여 충격반응 스펙트럼 시험을 실시하는데 진동시험기에서 허용하는 최대 힘, 속도, 변위에 의하여 제약을 받게 된다. 충격반응 스펙트럼을 만족하는 충격파형은 무수히 많으나 최대 가속도, 속도, 변위 등이 작으면 작을수록 그 충격파형의 품질이 우수하다고 말할 수 있다. 충격 지속시간이 짧고 충격가속도의 최대치가 큰 충격파형을 인가할 수 없지만, 충격 지속시간이 보다 길고 충격가속도의 최대치가 작은 파형이 동일한 충격반응 스펙트럼 규격을 만족할 수 있다. 진동시험기를 사용하여 충격반응 스펙트럼 시험을 수행하기 위한 충격파형이 웨이브레트를 이용하여 시험규격의 충격반응 스펙트럼을 만족하도록 합성된다. 웨이브레트의 매개변수는 주파수, 반파의 개수, 지연시간, 극성이다. 각 웨이브레트의 진폭은 시험규격의 충격반응 스펙트럼을 만족하도록·반복적으로 조절된다. 이렇게 합성된 충격파형은 진동시험기를 사용한 충격반응 스펙트럼 시험의 참조 가속도 파형으로 간주된다.

• Journal of the Korean Society for Railway
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• v.15 no.3
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• pp.217-223
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• 2012

This study describes an experimental investigation about the impact damage characteristics of various types of high speed train window glass. Kinds of impact test standards for glass were studied and impact test considering scattering ballast were developed. Windows with external impact side made with annealed, heat strengthened and tempered glasses are likely to be broken by sharp tipped falling object. Broken shape of annealed glass is like line in part and that of heat strengthened glass is line on the whole. Tempered glass is destroyed to pieces. The change of tip type from sharp to blunt makes the higher destroyed level. Tempered glass has higher strength than annealed glass with blunt tip. When the protective films are attached to glasses, strength against destruction increases. In case of real ballast test, glasses without protective films were destroyed, but those with protective films are hard to be broken.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1733-1740
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• 2010

The analysis of the dynamic behavior of the packaging of a drum washing machine has been carried out under the drop impact conditions. LS-DYNA software is used for performing the finite element analysis, and the validations are performed by comparing with the impact acceleration, effective stress and deformation of cushioned package with high-speed camera during free drop test. By analyzing the cushion characteristics and the design parameters of the original packaging, a packaging with an improved design is developed, and this design is validated on the basis of the results of the distribution test which consists of drop test, vibration test, stacking test, squeez test and so on. The drop impact simulation and analysis methods developed in this study can be adopted to successfully improve the cushioning provided by the packaging and to reduce the cost involved in developing new packaging for drum washing machines.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.04a
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• pp.24-24
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• 2000

작업 중 공구를 관에 떨어뜨리거나 작업하기 위해 관을 이동하던 중 다른 물체에 부딪힐 경우 복합재로 만들어진 관이 손상을 입게 되는 경우가 생기는데 관이 상황에 따라 얼마나 손상을 입었는지가 본 연구의 관심이다. 충격자는 직경이 25.4mm와 12.7mm인 반구형 2종류와 모서리의 직경이 15mm인 원추형 1종류로 각각 무게가 다르며, 떨어뜨리는 자유낙하 높이는 120mm에서 700mm로 종류에 따라 간격을 달리했다. 실험 장치로는 Dynatup 8250을 사용했으며 충격에너지, 최대충격하중, 충격변위, contact diameter를 측정했다. 시험 후 시편은 방사선 촬영을 하여 충격자의 종류에 따라 손상의 정도가 어떻게 다른지를 파악했다. 직경이 25.4mm인 반구형의 충격자는 표면의 손상은 적었으나 복합재 관의 내부에 delamination이 많이 생겼으며 직경이 12.7mm인 반구형의 충격자는 표면의 손상이 심했으나 내부의 delamination이 상대적으로 적었다. Contact diameter와 최대충격하중과의 관계는 실험치와 이론치가 잘 일치했으나 Kinetic energy와 최대충격하중과의 관계는 실험치와 이론치의 차이가 있었다.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.318-323
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• 1998

사용 후 핵연료 수송용기의 충돌사고에 대한 안전성은 층격완충체의 층격흡수특성에 지배되며, 충격완충체의 충격홉수특성은 외부의 케이스와 내부 격막판 둥의 철제 구조물과 내부에 삽입된 충격흡수재의 변형특성에 지배를 받는다. 충격흡수재를 감싸주는 철제 케이스와 내부 격막판의 용접 접합부는 일부 부분이 제작공정상 부득이 부분용접의 접합형태를 갖기 때문에 판재나 완전 접된 부분에 비해 강도가 약해 충돌사고시 취약부위가 파단된다. 이러한 케이스 용접부의 파단은 충격완충체의 변형특성을 변화시켜 충격흡수거동이 달라지는 원인이 된다. 따라서, 본 연구에서는 용접 접합부의 강도특성을 수송용기의 자유낙하 충돌해석에 적용할 수 있는 해석모델을 구성하고 부분용접된 접합부의 파단강도가 수송용기의 충돌거동에 미치는 영향을 분석하였다.