• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1552-1558
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• 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 Advanced Navigation Technology
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• v.7 no.2
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• pp.199-205
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• 2003

In this paper, CSMA/CA protocol is modified for aeronautical VHF communication through collision alleviation and the change of retransmission slot selection method in flag used transmission. When collision occurred in the contention period of CSMA/CA process, it is generally waiting for retransmission delay and it has the double size of CW(Contention Window). To solve this problem, this paper modifies the change procedure of original contention window size and reduces the state transition in collision among the whole of it. Also, in this paper we reduces the second collision probability through the station has to enter Backoff mode with increased contention window in the first collision. In the result of simulation, it is verified that it has good property in throughput and delay, So the proposed protocol is suitable for aeronautical VHF communication.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.433-436
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• 2010

본 논문에서는 파일형 선박충돌 방호공에 선박이 충돌하였을 때 방호공의 거동을 해석하였다. 방호공의 구조는 상부슬래브, RCP 말뚝 및 이를 지지하는 지반은 비선형 지반스프링으로 모델링 하였다. 상부슬래브 8절점요소로 모델링 하였으며 철근과 콘크리트로 구성되어있다. RCP 말뚝은 철근망과 충진콘크리트로 구성되어있으며 충돌 시 파괴거동을 표현할 수 있는 Damaged Plasticity로 모델을 사용하였고 Shell 요소로 모델링 하였다. 선박충돌 시 선박의 강성에 따른 거동 특성을 파악하기 위해 선박을 강체모델과 실제모델에 대한 해석을 수행하였다. 선박과 교량의 충돌은 정면충돌로 고려하였으며, 충돌속도는 3.3m/sec로 가정하였다. 선박과 방호공과의 충돌 해석은 비선형 해석 프로그램인 ABAQUS/Explicit을 이용하여 수행하였으며, 이를 통하여 선박 충돌 시 방호공의 에너지 거동을 분석하였다. 해석결과 선박의 강성이 커질수록 슬래브의 변형 및 소산 에너지량이 커지는 것을 확인할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1021-1026
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• 2011

Structural impact problems are becoming increasingly important for a modern defense industry, high-speed transportation, and other applications because of the weight reduction with high strength. In this study, a numerical investigation on the impact fracture behavior of aluminum plates was performed under various projectile conditions such as nose shapes, velocities, and incidence angles. In order to reduce the iterative numerical analysis, the Latin Square Method was employed. The influence factor was then determined by an FE analysis according to the conditions. The results were evaluated by means of a statistical significance interpretation using variance assessment. It was shown that the velocity and incidence angle can be the most important influence factors representing the impact absorption energy and plastic deformation, respectively.

• Proceedings of the Korean Society of Computer Information Conference
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• 2024.01a
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• pp.371-374
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• 2024

본 논문에서는 PBD(Position-based dynamics)를 이용한 옷감 시뮬레이션에서 페이스(Face) 및 에지(Edge)의 충돌/접촉을 처리할 때 나타나는 표면 떨림 문제를 SDF(Signed Distance Field) 접근법을 통해 안정적으로 해결할 수 있는 기법을 제안한다. 충돌 제약 조건을 이용한 충돌처리에서 나타나는 옷감 시뮬레이션의 떨림 현상을 개선하기 위해 본 논문에서는 페이스 및 에지 내부에 존재하는 충돌 지점의 속도를 충돌 법선 방향과 접선 방향으로 나누어 계산하는 과정을 거치며, 그 운동량을 페이스 및 에지에 포함된 연결된 정점(Vertex)에 전달한다. 본 논문에서 제안하는 기법은 일반적인 SDF 기반 충돌 처리에서 나타나는 충돌 시 떨림 현상을 개선하며, 기존의 방법보다 안정적인 SDF 충돌처리가 가능하기 때문에 다양한 변형체 재질을 시뮬레이션 할 때 활용될 수 있다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.217-226
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• 2018

Since the sides of a vehicle are designed asymmetrically unlike its front or rear, the degree of deformation of the car body greatly differs depending on the site of collision if a broadside collision takes place. When elastic deformation and plastic deformation occur in the car body occur due to a collision, the kinetic energy is absorbed into the body, and the momentum decreases. Generally, an analysis of traffic accidents analyzes the vehicle's behavior after a collision by the law of momentum conservation and corrects the error of the amount of energy absorption due to the deformation of the car body, applying a restitution coefficient. This study interpreted a finite element vehicle model applying the structure of the car body and the material properties of each part with LS-DYNA, analyzed the result and drew the restitution coefficient and the depth of penetration according to the contact area of the vehicle in a broadside collision between an SUV and a passenger car. When the finally calculated restitution coefficient and depth of penetration were applied to the examples of the actual traffic accidents, there was an effect on the improvement of the error in the result. It was found that when the initial input value, drawn using the finite element analysis model, it had a higher reliability of the interpretation than that of the existing analysis techniques.

• Journal of the Korean Society for Railway
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• v.16 no.3
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• pp.202-206
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• 2013

A submerged floating railway is an innovative tunnel infrastructure passing through the deep sea independent of wave and wind so that high speed trains can run on it. It doesn't depend on water depth and is cost effective due to modular construction on land. The construction period can be reduced drastically. This paper introduces the concept design of a submerged floating railway, and for securing safety, proposes a method to analyze the structural behavior of the body in case of collision with a submarine. The theory of a beam with an elastic foundation was used to calculate the equivalent mass of the body so that the perfect elastic collision could be applied to calculate the collision velocity. The maximum deformation and bending moment was analyzed based on energy conservation. To verify the results, a collision analysis using a finite element analysis code was made. Comparing the results confirmed that this simplified collision analysis method gives enough accurate deformation and bending moment to be used for actual estimation in the initial design stage.

• Journal of Aerospace System Engineering
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• v.18 no.4
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• pp.61-69
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• 2024

With increasing interest in aviation leisure sports, the demand for ultralight aircraft has increased, highlighting the necessity for robust structural design of the aircraft. In response, this study conducted static structural analysis and free-fall analysis of fuselage frame of ultralight aircraft. Robust design and crashworthiness under operational load conditions and vertical impact scenarios were evaluated by assessing maximum stress and safety factors. Analyses were performed using finite element method-based software ANSYS Workbench. Results including stress distribution and strain were analyzed to verify the safety of the designed fuselage frame. Additionally, this study predicted excessive deformation and failure locations of the fuselage frame during vertical drop impacts.

• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.300-310
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• 2008

Through this study, a conceptual design for the next generation high-speed EMU has been derived to meet the crash worthiness requirements of the Korean rollingstock safety regulation. The crashworthiness regulations require some performance requirements for two heavy collision accident scenarios; a train-to-train collision at the relative speed of 36 km/h, and a collision against a standard deformable obstacle of 15 ton at 110km/h. The complete train set will be composed of 2TC-6M with 13 ton axle load, which is different from KTX with the power car of 17 ton axle load. Using theoretical and numerical analyses, a crashworthy conceptual design was derived in terms of mean crush forces and energy absorptions for principal crushable structures and devices. The derived conceptual design was evaluated and improved using one dimensional dynamic simulations for the bar-spring-damper-mass model. It is shown from the simulation results that the suggested conceptual design can easily satisfy domestic crashworthiness requirements.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.139-146
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• 2010

In this study, a new equivalent modeling technique of rollingstock for 1-D collision dynamics was proposed using crash analysis of 3-D finite element model in some detail. To obtain good simulation results of 1-D dynamic model, the force-deformation curves of crushable structures should be well modelled with crash analysis of 3-D finite element model. Up to now, the force-deformation curves of the crushable structures have been extracted from crash analyses of sectionally partitioned parts of the carbody, and integrated into 1-D dynamic model. However, the results of the 1-D model were not satisfactory in terms of crash accelerations. To improve this problem, the force-deformation curves of the crushable structures were extracted from collision analysis of a simplified train consist in this study. A comparative study applying the suggested technique shows in good agreements in simulation results between two models for KHST.