• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.97-104
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• 2000

Pneumatic cylinder is widely used for mechanical handling systems. Often, the impact occurs at the both ends points of pneumatic cylinder and generates destructive shock with in the structural operating members of the machine or equipment. To reduce the damage of system, therefore, shock absorbing devices are required. Cushioning of pneumatic cylinders at one or both ends of piston stroke is used to reduce the shock and vibration. The cylinder body have to withstand under high velocity and load. In this research, the pneumatic cushioning cylinder moving tests have been conducted for different load mass and supply pressure. The velocity of pneumatic cylinder actuation system with multiple orifice cushion sleeve which is set vertically controled with meter-in/out system. This study examines the dynamic characteristics of pneumatic cylinder with cushion devices. It turns out that the cushion pressure is mainly a function of the external load rather than the supply pressure. The cushion region characteristics was also revealed in the meter-in system.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.328-336
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• 2002

decrease in efficiency due to cavity fluid fluctuation. The purpose of this study is to examine erosion aspect on the SS400 specimen by cavitation and the effect of impact pressure generated from the demolition of the cavity of ultrasonic vibrator horn in the marine sludge oil environment. The erosion damage of specimen was investigated mainly on weight loss, weight loss rate and maximum erosion rate with variation of the vibration amplitude of $50{\mu}m, 24{\mu}m$ as well as the change of space between transducer horn and specimen. The experimental results showed that as the space between ultrasonic vibrator horn and specimen disk increased, the weight loss and weight loss rate decreased and the values were larger in SFO than in SLO. These findings would help interpret the aspect of cavitation erosion damage in metallic materials of different operating environment and material characteristics.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.158-165
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• 2003

A specific experimental method, the Split Hopkinson pressure bar (SHPB) technique has been widely used to determine the dynamic material properties under the impact compressive loading conditions with strain rate of the order of 10$^3$/s∼l0$^4$/s. In this paper, dynamic deformation behaviors of rubber materials widely used for the isolation of vibration from structure under varying dynamic loading are determined by using plastic SHPB technique. A transition point to scope with the dynamic deformation behavior of rubber-like material is defined in this paper and used to characterize the specifics of the dynamic deformation of rubber materials.

• Journal of KSNVE
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• v.7 no.3
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• pp.439-447
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• 1997

In this study, the dynamic instabilities of a nonlinear elastic system subjected to follower forces are investigated. The two-degree-of-freedom double pendulum model with nonlinear geometry, cubic spring, and linear viscous damping is used for the study. The constant, the initial impact forces acting at the end of the model are considered. The chaotic nature of the system is identified using the standard methods, such as time histories, power density spectrum, and Poincare maps. The responses are chaotic and unpredictable due to the sensitivity to initial conditions. The sensitivities to parameters, such as geometric initial imperfections, magnitude of follower force, direction control constant, and viscous damping, etc., are analysed. Dynamic buckling loads are computed for various parameters, where the loads are changed drastically for the small change of parameters.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.130-141
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• 2000

The virbration characteristics of a passenger car steering column are studied by using a modal test and a finite element (FE) analysis. To verify the FE model and the results, an experiment using the impact exciting method is performed. Two types of the steering column in this study are considered as follows; (ⅰ) the non-tilt type steering column and (ⅱ) the upper-tilt type steering column. The experimental results are compared with those o the FE analysis, and it ti shown that the results agree with each other. The effects of various design parameters such as the bracket thickness, the column diameter on the natural frequencies are also investigated by FE analysis.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.341-346
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• 2003

과실 포장화물(packaged freight)은 과실, 완충재 및 겉포장 상자로 구성되며, 속포장(내포장)하지 않는 것이 식품 포장이나 다른 포장과 구별된다. 그러나 과실 개개를 보호하기 위한 낱포장(단위포장)은 중요시되며, 사용되는 완충재가 이 기능을 한다. 과실 포장에 사용되는 겉포장 상자는 제품 취급의 편리성을 도모할 뿐만 아니라, 물류 과정 중에 제품의 보호와 상품에 대한 정보를 제공하는 포장 역할의 주체가 된다. 또한 완충재는 포장물에 전달되는 충격과 진동 등의 외력 완화와 응력 분산, 포장물의 표면보호, 상호간의 접촉방지 및 이동방지의 기능을 수행한다. 종전까지는 골판지 상자에 의한 포장화물 단위로 취급되는 경우가 대부분 이었는데, 농산물의 물류합리화와 물류비 절감 문제가 본격 대두되면서, 팰리트를 활용한 단위화물 적재 시스템(ULS) 즉, 팰리트 화물(palletized freight) 상태로 취급되는 경우가 점차 확대되고 있고 정부에서도 이를 적극 지원하고 있다. (중략)

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.191-192
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• 2008

In this paper, we investigated on the characteristics and assessment of the insulators damaged by hitting tester(ST-100, Sharp-Eng, KOR). It made that an apparatus act on KS C 3801 for the damaged characteristics and assessment of insulators according to external scattering objects. There are selected 255mm glass insulators and 254mm porcelain insulators as the specimen. The hitting angles of the damaged insulator by pendulum weight are at $72^{\circ}$. At these points, velocity of pendulum weight is about 3.04m/sec and the force is 58.16N. At the hitting angle of 26 degrees, glass insulator is diffused the vibration within it but porcelain insulator is not. The inside vibrations of glass insulator and porcelain insulator are as like as two at the hitting angle of 53 degrees. The damaged glass insulator at the hitting angle of 72 degrees hardly is not diffused.

• Journal of the Korean Society of Safety
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• v.25 no.5
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• pp.39-43
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• 2010

The surfacing of bridge-decks are object to secure trafficability and to protect bridge face from impact load of traffic volume and other external conditions. But the deformation of pavements and cracks happen due to the damage of the bridge-decks surfacing from the increase of the traffic, short maintenance period and continuous vibration of bridge. This test is to make the 3-type high performance concrete that has different mixing ratio and is added the blast furnace slag, fly ash and silica respectively, and to compare 3-type high performance concrete of normal high strength concrete of $400kgf/cm^2$ strength through the static loading test and fatigue test. And test specimen is united floor slab and pavement for the durability of bridge.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1174-1179
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• 2004

Field tests were conducted to investigate effects of a rail joint on the dynamic behavior of railway bridge. A four-span simpled supported plate girder bridge which has a rail joint on the third span was selected for tests. At the operating train loading, the induced vibration of the first and third span has been examined. The dynamic magnification ratio was used for quantitative analysis of impact effects caused by rail joint. The result of tests show that dynamic behavior of railway bridge picked up considerably due to a rail joint.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.52-57
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• 2003

This study suggests several ways to improve the railroad facilities in the urban areas so as to maintain the urban railroad facilities and minimize their adverse impact on the roads around the facilities. Environmental problems such as noise and vibration can be minimized by constructing soundproofing walls and improving railway and train systems. To reduce the traffic congestion at the railroad crossings, current at-grade crossings should be changed to separated crossings. Moreover, the criteria by where railroad crossings are located should be revised. In the long term, the land use development for the railroad station and the surrounding areas needs to be changed. Several case studies of Japan's and France's major cities show the potential of successfully integrating the development of railroad facilities and their surrounding areas. In addition, there is a need to .consider institutional aspects, to improve the railroad facilities in the urban areas and to allow the integrated development of the railroad facilities and the surrounding areas.