• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.265-274
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• 2015

The structural safety of nuclear power plant against impact from aircraft crash has been performed so far in two viewpoints such as local behavior and global behavior, and the local behavior has been evaluated using local damage evaluation formulas suggested based on the results of experimental data of RC (Reinforcement Concrete) wall. However, few data have been collected from recent research to evaluate the local behavior and damage of SC (Steel plate reinforced Concrete) wall, which is recently applied to the newly designed nuclear power plant. In this study, local damages of SC wall and RC wall against an idealized aircraft engine projectile impact are evaluated through FE simulation analyses with various wall thicknesses and steel ratio. Through analysis of local collision simulation results of SC and RC wall, the penetration depth of SC wall and RC wall are compared.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1A
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• pp.25-33
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• 2011

The impact damage behavior of steel-strengthened concrete panels exposed to explosive loading is investigated. Since real explosion experiments require the vast costs to facilities as well as the blast and impact damage mechanisms are too complicated, numerical analysis has lately become a subject of special attention. However, for engineering problems involving blast wave and fragment impact, there is no single numerical method that is appropriate to the various problems. In order to evaluate the retrofit performance of a steel-strengthened concrete panel subject to blast wave and fragment impact loading, an explicit analysis program, AUTODYN is used in this work. The multi-solver coupling methods such as Euler-Lagrange and SPH-Lagrange coupling method in order to improve efficiency and accuracy of numerical analysis is implemented. The simplified and idealized two dimensional and axisymmetric models are used in order to obtain a reasonable computation running time. As a result of the analysis, concrete panels subject to either blast wave or fragment impact loading without the steel plate are shown the scabbing and perforation. The perforation can be prevented by concrete panels reinforced with steel plate. The numerical results show good agreement with the results of the experiments.

• Composites Research
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• v.34 no.2
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• pp.115-122
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• 2021

SMC(Sheet molding compound) composite is mainly used for forming of vehicle's body. Considering the car accident, it is essential to research the impact behavior and characteristics of materials. It is difficult to identify them because the impact process is completed in a short time. Therefore, the impact damage analysis using FE(finite element) model is required for the impact behavior. The impact damage analysis requires the parameters for the damage model of SMC composite. In this paper, ANN(artificial neural network) technique is applied to obtain the parameters for the damage model of SMC composite. The surrogate model by ANN was constructed with the result in LS-DYNA. By comparing the absorption energy in drop weight test with the result of ANN model, the optimized parameters were obtained. The acquired parameters were validated by comparing the results of the experiment, the FE model and the ANN model.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.3
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• pp.41-48
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• 2010

In this paper, the analysis of impact damage behavior of a reinforced concrete structure that undergoes both a shock impulsive loading and an impact loading due to the air blast induced from an explosion is performed. Firstly, a pair of multiple loadings are selected from the scenario that an imaginary explosion accident is assumed. The RC structures strengthened with advanced composite materials (ACM) are considered as a scheme for retrofitting RC wall structures subjected to multiple explosive loadings and then the evaluation of the resistant performance against them is presented in comparison with the result of the evaluation of a RC structure without a retrofit. Also, in order to derive the result of the analysis similar to that of real explosion experiments, which require the vast investment and expense for facilities, the constitutive equation and the equation of state (EOS) which can describe the real impact and shock phenomena accurately are included with them. In addition, the numerical simulations of two concrete structures are achieved using AUTODYN-3D, an explicit analysis program, in order to prove the retrofit performance of a ACM-strengthened RC wall structure.

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

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.844-846
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• 2011

충돌에서의 차체 손상과 충돌 성능 강화를 위하여 최근 크래쉬 영역의 개념이 설계개념에 도입되고 있다. 대표적인 예가 범퍼와 차체사이의 크래쉬 박스로 저속충돌시 충격에너지를 흡수하여 범퍼이후 차체에 에너지를 저감시켜 차량의 안전성 및 수리비 저감 등에 있어서도 매우 효과적인 역할을 하는 부품으로 이에 대한 개발을 위해 많은 연구들이 진행되고 있다. 본 논문에서는 충돌에너지 흡수성능이 우수한 크래쉬박스에 알루미늄 폼을 적용하였을 때 충돌에너지 흡수 및 거동에 대하여 충돌해석을 수행하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.5-5
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• 2021

최근 기후변화로 인해 예측이 어려운 국지성 호우가 빈번하게 발생하고 있다. 국지성 호우는 대량의 홍수를 일으키고 산사태와 유송잡물을 동반한 흐름을 야기할 수 있으며 이로 말미암아 인근의 초목과 식생들로부터 유목(driftwood)이 발생하기도 한다. 유목이 흐름과 함께 떠내려 오게 되면 그로 인한 운동에너지가 크게 발생하게 되며, 수공구조물과 주택가옥 등에 충돌시, 순수한 수류의 충돌보다 훨씬 큰 손상을 주기도 한다. 또한 유목이 수공구조물 인근 하상에 군집하면 통수능을 저하시키기도 하며 식생효과와 마찬가지로 유목주변으로 유속이 증가하면서 세굴현상이 발생하게 되는데, 이는 하상저하를 일으키며 수공구조물의 안정성에 지속적으로 피해를 줄 수 있다. 특히 군집된 유목들이 교각에 충격을 주면 흐름방향으로 교각에 작용하는 외력을 증가시키게 되고 군집된 유목들이 다른 유목들을 연쇄적으로 포착하는 동시에 흐름을 지속적으로 방해하여 수위상승을 야기하게 된다. 이는 유목주변으로 세굴을 발생시켜 교량의 붕괴를 촉진시킬 수 있다. 일본의 경우에는 대부분의 하천유역의 경사가 매우 급하기 때문에 홍수발생시 산사태와 유송잡물들이 빈번하게 발생하고 있다. 그에 따라 대량의 유목들이 하천으로 유입되어 하천의 수공구조물과 주거지역에 심각한 피해를 주는 경우도 많다. 따라서 유목의 거동과 군집현상을 이해하여 사전에 유목거동의 예측과 유목과 하상변동의 상호작용 분석을 통해 유목에 의한 수리구조물 피해를 예측하는 연구들이 필요할 것으로 판단된다. 본 연구는 유목의 거동과 군집양상을 예측분석하기 위해 유목과 흐름의 이동상 실내실험과 수치해석을 수행하여 유목유입량에 따른 하상변동과 유목의 하상퇴적양상 및 다양한 거동을 관측분석 하였다. 특히, 유목간의 상호충돌과 측벽충돌을 고려하는 수치모듈을 유목동역학모형에 적용하여 수치해석을 수행하였다. 이를 통해 이동상 하상에서의 유목의 군집과정을 분석하고 수치해석의 한계와 개선사항들을 논의하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1065-1075
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• 2017

In this study, high velocity impact tests along with modeling of material behavior and numerical analyses were conducted to predict the dispersion behavior of the debris resulting from a high velocity impact fracture. For the impact tests, two different materials were employed for both the projectile and the target plate - the first setup employed aluminum alloy while the second employed steel. The projectile impacts the target plate with a velocity of approximately 1 km/s were enforced to generate the impact damages in the aluminum witness plate through the fracture debris. It was confirmed that, depending on the material employed, the debris dispersion behavior as well as the dispersion radii on the witness plate varied. A numerical analysis was conducted for the same impact test conditions. The smoothed particle hydrodynamics (SPH)-finite element (FE) coupled technique was then applied to model the fracture and damage upon the debris. The experimental and numerical results for the diameters of the perforation holes in the target plate and the debris dispersion radii on the witness plate were in agreement within a 5％ error. In addition, the impact test using steel was found to be more threatening as proven by the larger debris dispersion radius.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.3
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• pp.58-64
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• 2007

It is well known that the aircraft engine inlet should be safely designed against the bird strike at the aircraft development stage. The aircraft accident is increasing for FOD(Foreign Object Damage), especially bird of runway circumference. The aircraft accident due to bird strike brings about economic loss which is connected with the life of passengers. In this study, MSC/DYTRAN has been utilized to analyze the aircraft engine inlet against the bird strike. In order to validate the proposed method for the bird strike analysis, this study was performed with comparison of precedence study results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.457-467
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• 2016

In this study, we investigate the dispersion behavior of debris and debris cloud generated by high-velocity impacts using the smoothed particle hydrodynamics (SPH) technique. The projectile and target plate were made of aluminum, and we confirm the validity of the SPH technique by comparing the measured major and minor axis lengths of the debris cloud in the reference with the predicted values obtained through the SPH analysis. We perform high-velocity impact and fracture analysis based on the verified SPH technique within the velocity ranges of 1.5~4 km/s, and we evaluate the dispersion behavior of debris induced by the impact in terms of its kinetic energy. The maximum dispersion radius of the debris on the witness plates located behind the target plate was increased with increasing impact velocity. We derive an empirical equation that is capable of predicting the dispersion radius, and we found that 95％ of the total kinetic energy of the debris was concentrated within 50％ of the maximum dispersion radius.