• Journal of the Korean Society for Railway
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• v.3 no.1
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• pp.27-33
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• 2000

In this paper, numerically evaluated is the crashworthiness of the new design of the standard Korea Electric Multiple Unit Train(K-EMU)[developed by the Korea Railway Research Institute]. The 4-car consist of K-EMU is analyzed under collision conditions such as normal coupling, heavy shunting, light collision and heavy collision to collide against another stationary one at 5 kph, 10 kph, 25 kph and 32 kph, respectively. Energy absorbing capacity of its draftgear commercially available in the market and to be equipped in K-EMU is evaluated under each collision condition. Analytical results show that draftgear only is not enough to provide necessary energy absorbing capacity. It is therefore concluded that additional energy absorbers like mechanical fuses should be adopted to improve the crashworthiness of K-EMU.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.103-107
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• 2001

When ship claps against the ocean structure sited at shallow water, the time simulation of motion responses of dolphin-moored ocean structure is presented. The equatien of motion based on Cummin's theory of impulse responses are employed, and solved in time domain by using the Newmark $\beta$ method. The added mass and damping coefficients involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The impact forces due to ship collision are modeled as two method, and those are elastic and non-elastic collisions. The mooring forces for dolphin systems of scean structure are considered as linear spring system.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.663-666
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• 2004

An analysis of the annual frequency of collapse(AF) is performed for each bridge pier exposed to ship collision. AF is computed for each bridge component and vessel classification. The summation of AFs computed over all of the vessel classification intervals for a specific component should equal the annual frequency of collapse of the component. The designer should use judgment in developing a distribution of the vessel frequency data based on discrete groupings or categories of vessel size by DWT. In the present study the effect of vessel classification on the annual frequency of collapse in the ship collision risk assessment is investigated by illustrative numerical examples based on the vessel frequency data of the domestic harbor. The DWT interval for larger vessels has more effect on the ship collision risk. Therefore the expert judgement in determining the larger DWT interval is required because the design impact lateral resistances of bridge components depend on the ship collision risk.

• Transactions of Materials Processing
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• v.33 no.5
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• pp.309-314
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• 2024

Supersonic aircraft and missiles often encounter damage issues due to high-speed collisions with small objects such as ice particles and water droplets. This can significantly impact the safety and performance of these vehicles, making the assessment and development of collision testing crucial. Existing collision testing methods have relied on equipment such as gas guns, which utilize high pressure. However, most accelerators for projectiles are large-scale devices designed for weaponry and high-pressure gases, rendering them inaccessible and unsuitable for laboratory use. Therefore, there is a need for research into easily accessible and economically efficient testing devices at the laboratory level. An impact tester can launch a projectile with a velocity of 100 m/s using low-pressure compressed air at approximately 10 bar. The velocity of the impact tester projectile is determined by the pressure within the chamber, friction, and the length of the barrel. In this study, computational fluid dynamics was utilized to define friction coefficients that match experimental results based on projectile weight, enabling accurate prediction of velocity. The resulting data provides practical and effective insights for the design of impact testers, utilizing the defined friction coefficients to understand and predict complex physical phenomena.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.49.1-49.1
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• 2016

Solar System has evolved with numerous collisions among asteroids. Ancient catastrophic collisions of large parent bodies led the formation of asteroid families and relevant dustband structures up to the present day, and it would be interesting to address a question - "what happens if an asteroid collides with another asteroid?" Recent discoveries of "active asteroids" in the main-belt have attracted interest for their potential to witness a catastrophic collision in the current Solar System. So far, however, there is no direct evidence for catastrophic collision on active asteroids while several objects have been confirmed for other mechanisms (e.g., 596 Scheila for impact cratering, P/2013 R3 and P/2013 P5 for rotational breakup). The most potential candidate for catastrophic collision could be a sub-km active asteroid P/2010 A2, which is still controversial on its driving mechanism, but if confirmed, would have made P/2010 A2 the unique example of catastrophic collision on the current main asteroid belt. In this presentation, we revisit all of archival data of P/2010 A2 in a combination with our own observation using Subaru/Suprime-Cam on 2011 June, where we have a great benefit of a large orbital coverage. We found a grain size dependence of dust ejection velocity from P/2010 A2 (a power-law size distribution with an index of k~ -1/10), which is favorable to a catastrophic disruption scenario in agreement with laboratory impact experiments. At this conference, we plan to provide our understanding of the morphology of P/2010 A2 through a perspective of catastrophic collision.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.7
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• pp.567-578
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• 2015

Single droplet-wall collision heat transfer characteristics on a heated plate above Leidenfrost temperature were experimentally investigated considering the effects of impact velocity. The collision characteristics of the droplet impinged on the heated wall and the changes in temperature distribution were simultaneously measured using synchronized high-speed video and infrared cameras. The surface heat flux distribution was obtained by solving the three-dimensional transient heat conduction equation for the heated substrate using the measured surface temperature data as the boundary condition for the collision surface. As the normal impact velocity increased, heat transfer effectiveness increased because of an increase in the maximum spreading diameter and a decrease in the vapor film thickness between the droplet and heated wall. For We < 30, droplets stably rebounded from a heated wall without breakup. However, the droplets broke up into small droplets for We > 30. The tendency of the heat transfer to increase with increasing impact velocity was degraded by the transition from the rebounding region to the breakup region; this was resulted from the reduction in the effective heat transfer area enlargement due to the breakup phenomenon.

• Journal of the Korean Society for Railway
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• v.10 no.4
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• pp.381-387
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• 2007

In this paper, crashworthiness of the EMU carbody of Incheon Metro is numerically evaluated against two types of overhead line structures (headspan and portal-type). The material of the EMU carbody is stainless steel (SUS301L), and that of the overhead line structures is the structural steel (SS400). The EMU carbody is analyzed under collision conditions, such as upright side-on impact, side-on roof impact and angled roof impact scenarios, to be collided against the headspan type or the portal type at the speed of 64.4km/h, respectively. It is concluded from the numerical results that the overhead line structures will not do so much harm to the EMU carbody of Incheon Metro for various collisions caused by derailment. Furthermore, the overhead line structure of the portal type is superior to that of the headspan type in the crashworthy point of view.

• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.14-19
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• 2014

The global demand for reduction in the weight of automobiles has led many countries to focus on the development of hybrid, eco-friendly, and electric cars. Reduction in the weight of materials can both increase fuel efficiency and maximize automobile performance. Therefore, the design of automobile should be inclined towards the safety aspects. but at the same time, it also consider reducing the structural weight of an automobile. In this study, CFRP side members with circular and double hat shaped section was manufactured. The impact collapse tests performed with change of the stacking condition, such as variation of interface number and outerlayer angle. The impact collapse load and absorbed energy were quantitatively analyzed according to the changes in section shapes and stacking condition. This analysis was performed to obtain design data that can be applied in the development of optimum lightweight members for automobiles.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.4
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• pp.182-190
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• 2020

This study reports a series of drop impact tests performed to generate denting damages on stiffened plates and their residual ultimate strength tests under axial compression. The models were fabricated of general structural steel, and each model has six longitudinal stiffeners and two transverse frames. Among six fabricated models, four were damaged, and two were left intact for reference. To investigate the effects of collision velocity and impact location on the extent of damage, the drop height and the impact location were changed in each impact test. After performing the collision tests, the ultimate axial compression tests were conducted to investigate the residual strengths of the damaged stiffened plates. Finite element analyses were also carried out using a commercial package Abaqus/Explicit. The material properties obtained from a quasi-static tensile tests were used, and the strain-rate sensitivity was considered. After importing the collision simulation results, the ultimate strength calculations were carried out and their results were compared with the test data for the validation of the finite element analysis method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.402-408
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• 2021

Vehicle engineering analysis in the event of an accident caused by a car built on mechanical design has not been investigated in-depth but relies on the subjective experience knowledge of the investigator. This study analyzed the correlation between the speed, progress, steering, and braking before impact, which is consistent with the final stop position, by drawing a site situation chart using the CAD (CAD) program and repeating 250 crashes using the PC-Crash program. The following situations were investigated: lower impact velocity; greater impact speed of the vehicle, which is not affected significantly by the departure angle; higher vehicle speed, such as the effective impact velocity, after the impact; higher vehicle speed; and lower vehicle speed. (Ed note: I am unsure what you are saying here. It appears contradictory and not a complete sentence. Please check the changes.)The simulation results of this study identified the process of returning to the magnetic progression lane after recognizing the opposite porter while Mighty was carried out on the uphill left-curve section in a position that crossed the center line, and the collision of the porter's front left side, pushing the porter in the right diagonal direction and making the front stop towards approximately 11 o'clock.