• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.4
• /
• pp.1552-1558
• /
• 2011

In this paper, the automotive beam using aluminium foam is designed and the impact analysis is carried out. The analysis model is the beam of actual size with B- type section structure. At the frontal crash of low speed, ANSYS AUTODYN is used by predicting the behavior of deformation and its internal energy. By the use of 7075-T6 aluminum alloy, the weight is reduced as much as 55% than steel. The deformation at the bumper foam of aluminum is similar with that of steel and the impact energy reduction at aluminum is more than steel. The foam filled with aluminum as much as 50 % has more impact energy absorption than the completely filled aluminum foam.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.8 no.4
• /
• pp.47-52
• /
• 2008

Important factor in designing a breakaway sign support is the velocity change of the impact vehicle. It is measured from the crash test or can be calculated by 3-D Finite Element Analysis. It can also be calculated with relative ease utilizing energy and momentum conservation. In this paper a formula to calculate the velocity change of a car during the time of impact against a small sign is derived utilizing the energy and momentum balance. Using the formula, parametric studies were conducted to find that impact speed, separation force and Breakaway Fracture Energy(BFE) of the posts which represent the degree of fixedness to the foundation are the important factor to vehicle's speed change. It is shown that speed change is larger in the lower speed impact and to the posts with large separation force and BFE.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.4
• /
• pp.601-609
• /
• 2022

Jack-up drilling rigs are mobile offshore platforms widely used in the offshore oil and gas exploration industry. These are independent, three-legged, self-elevating units with a cantilevered drilling facility for drilling and production. A typical jack-up rig includes a triangular hull, a tower derrick, a cantilever, a jackcase, living quarters and legs which comprise three-chord, open-truss, X-braced structure with a spudcan. Generally, jack-up rigs can only operate in water depths ranging from 130m to 170m. Recently, there has been an increasing demand for jack-up rigs for operating at deeper water levels and harsher environmental conditions such as waves, currents and wind loads. All static and dynamic loads are supported through legs in the jack-up mode. The most important issue by society is to secure the safety of the leg structure against collision that causes large instantaneous impact energy. In this study, nonlinear FE -analysis and verification of the requirement against collision for 35MJ recommended by DNV was performed using LS-Dyna software. The colliding ship used a 7,500ton of shore supply vessel, and five scenarios of collisions were selected. From the results, all conditions do not satisfy the class requirement of 35MJ. The loading conditions associated with chord collision are reasonable collision energy of 15M and brace collisions are 6MJ. Therefore, it can be confirmed that the identical collision criteria by DNV need to be modified based on collision scenarios and colliding members.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.1 no.2
• /
• pp.82-95
• /
• 1998

In this paper, two series of numerical simulations are performed using LS/DYNA3D: The first series of numerical simulations are collision events between a 310,000 DWT double hull VLCC (struck ship) and two 35,000 and 105,000 DWT tankers (striking ships). Collisions are assumed to occur at the middle of the VLCC with the striking ships moving at right angle to the YLCC centerline. The second ones, grounding accidents of two 40,000 DWT Conventional and Advanced Double Hull lanker bottom structures, CONV/PD328 and ADH/PD328 models. The overall objective of this study is to understand the structural failure and energy absorbing mechanisms during collision and grounding events for double hull tanker side and bottom structures, which lead to the initiation of inner shell rupture and cause the kinetic energy dissipation to bring the ship to a stop. These numerical simulations will contribute to the estimation of damage extents of collision and grounding accidents and the future improvements in lanker safety at the design stage.

• Electrical & Electronic Materials
• /
• v.4 no.2
• /
• pp.143-149
• /
• 1991

전계가 인가된 H$_{2}$와 CO기체중을 통과하는 전자의 탄성과 비탄성 충돌 단면적을 볼츠만방정식을 이용하여 추정하였는데 충돌 단면적은 운동량변환, 진동여기, 해리, 전자 여기 및 전리 충돌 단면적을 이동속도의 측정값 및 계산값을 비교하므로써 결정하였다. Gibson과 Phelps가 각각 계산한 H$_{2}$ 및 CO의 운동량변환 충돌단면적을 본 연구의 결과와 비교하였으며 이를 기초로하여 온도는 293.deg.K, 상대전계의 세기 E/N은 1*$10^{-17}$ [V$cm^{2}$].leq.E/N.leq.200*10 $^{17}$ [V$cm^{2}$]의 범위에서 전자에너지 분포함수를 산출하였으며 이렇게 산출된 에너지 분포함수 및 충돌단면적은 실험적으로 측정한 모든 수송계수의 값들을 만족하였다.

• Electrical & Electronic Materials
• /
• v.3 no.2
• /
• pp.138-146
• /
• 1990

볼츠만 수송방정식에 관한 홀스타인의 식을 사용하여 온도는 273.deg.K, 상대전계의 세기가 1.leq.E/P..leq.30(V/cm Torr)인 때의 Na와 He 단일기체중을 통과하는 전자의 에너지분포함수와 수송계수를 계산하였다. 그리고 전자 이동속도의 결과치를 실험값과 비교하였으며 실험치와 계산치가 일치하도록 충돌단면적을 수정하여 계산에 적용하였다. 이러한 방법으로 Hesms 0.1[eV]-50[eV]까지 Na는 0.1[eV]-5[eV]까지의 에너지범위에서 결정된 운동량변환단면적의 값은 제한된 범위에서 Crompton 및 Nakamura의 값과 거의 일치하였다. 또한 이와 같이하여 계산된 Na와 He 단일기체의 충돌단면적을 이용하여 온도는 273.degK, 상대전계의 세기는 1.leq.E/P$_{o}$ .leq.30(V/cm Torr)의 범위에서 Na-He 혼합증기의 혼합비율을 He:Na는 99.5:0.5, 99:1, 9:1. 1:1로 변화시켜 특성에너지, 평균에너지, 전자이동속도, 전자에너지 분포함수를 게산하였다.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.22 no.6
• /
• pp.593-599
• /
• 2016

Incheon Bridge is 13.38 km long with an 800 m span, connecting Incheon International Airport and Songdo International City, Per hour 73.8 vessels navigate this space. The purpose of this study was to suggest a safe passing speed based on the displacement of a vessel based on the safety criteria of Incheon Bridge's anti-collision fence, which was designed during its initial construction. As AASHTO LRFD suggested, vessel collision energy, vessel collision velocity, and the hydrodynamic mass coefficient were considered to derive a safe vessel traffic speed. Incheon Bridge's anti-collision fence was designed so that 100,000 DWT vessels can navigate at a speed of 10 knot. This research suggests a safe speed for vessel traffic through a comparative analysis of an experimental ship's (300,000 DWT) speed and cargo conditions, regulation speed has been calculated according to the collision energy under each set of conditions. Additionally, safe traffic vessel's safe speed was analyzed with reference to tidal levels. Results from the experimental ship showed that a vessel of maximum 150,000 DWT is able to pass Incheon Bridge at a maximum of 7 knots with an above average water level, and is able to pass the bridge with a maximum of 8 knots under ballast conditions.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.12
• /
• pp.8966-8976
• /
• 2015

Unshielded posts on roadside are a critical hazard to the safety of impact vehicle to the posts. A crashworthy post is developed. In the first phase, it dissipates the impact energy by the linear momentum conservation principle while the plastic impact between the post and vehicle takes place, then, the second phase dissipation follows by the deformation of the energy absorbing modules embedded in the guide trough of the foundation. Simulations of impacts to a rigidly connected post and crashworthy post were made using LS-DYNA program, which demonstrated the danger of unshielded rigidly connected post and the effectiveness of the proposed crashworthy post to the 0.9ton-80km/h impact.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.1
• /
• pp.25-33
• /
• 2020

In this study, parametric analyses are performed using the coupled Eulerian-Lagrangian scheme for the collision behaviors of a vessel and an underwater slope that constitutes part of an artificial protective island. The vessel parameters considered in the analysis are bow angle, stem angle, draft, and impact velocity. The gradient of the slope, the friction coefficient between the bow and the slope, and soil strength are considered as parameters of the slope. For each parameter, the dissipated collision energy and the collision force are estimated from the behavior of the vessel, and the energy dissipation mechanism is identified in terms of the ground deformation. The collision force is assumed as an exponential function, and the effects of the parameters are estimated. As a result, only two parameters, the gradient of the slope and the friction coefficient between the vessel and the soil, can affect the exponential coefficient of the function. The dissipated energy by the soil can thus be estimated adequately. The relationship between the volume of the soil pushed out by the bow and the dissipated collision energy is estimated as a linear function. This relationship is independent of the magnitude of the collision energy, and affected more by the friction coefficient and the soil strength than by the parameters of the vessel.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.5
• /
• pp.297-302
• /
• 2020

Korea has many mountainous regions, and slope collapse that can lead to damage in road facilities and loss of lives often occurs. Rockfall-protection facilities are necessary to reduce such damages. Among these facilities, the standard Korean rockfall-protection fence is designed to resist 50 kJ of rockfall impact energy. However, the range of rockfall energy significantly varies depending on the condition of the slope, and it sometimes reaches up to 100 kJ. Thus, providing several types of standardized rockfall-protection fence is necessary to address the different rockfall impact energy for efficient response to rockfalls. This paper presents a study on standardized rockfall-protection fence for various rockfall impact energy using finite-element analysis. According to the results, standardized rockfall-protection fences against rockfall impact energy of 30 and 100 kJ were proposed and have been verified.