• International Journal of Automotive Technology
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• 제1권1호
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• pp.35-41
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• 2000

The crashworthiness of vehicles with finite element methods depends on the geometry modeling and the material properties. The vehicle body structures are generally composed of various members such as frames, stamped panels and deep-drawn parts from sheet metals. In order to ensure the impact characteristics of auto-body structures, the dynamic behavior of sheet metals must be examined to provide the appropriate constitutive relation. In this paper, high strain-rate tensile tests have been carried out with a tension type split Hopkinson bar apparatus specially designed for sheet metals. Experimental results from both static and dynamic tests with the tension split Hopkinson bar apparatus are interpolated to construct the Johnson-Cook and a modified Johnson-Cook equation as the constitutive relation, that should be applied to simulation of the dynamic behavior of auto-body structures. Simulation of auto-body structures has been carried out with an elasto-plastic finite element method with explicit time integration. The stress integration scheme with the plastic predictor-elastic corrector method is adopted in order to accurately keep track of the stress-strain relation for the rate-dependent model accurately. The crashworthiness of the structure with quasi-static constitutive relation is compared to the one with the rate-dependent constitutive model. Numerical simulation has been carried out for frontal frames and a hood of an automobile. Deformed shapes and the Impact energy absorption of the structure are investigated with the variation of the strain rate.

• 한국CDE학회논문집
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• 제18권6호
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• pp.461-469
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• 2013

Computer simulation with FEM is very useful to analyze hypervelocity impact phenomena that are tremendously expensive or otherwise too impractical to analyze experimentally. Shock physics can be efficiently handled by mesh adaptation which allows finite element mesh to be locally optimized to resolve moving shock wave in explosion. In this paper, an adaptive meshing technique based upon quadtree data structure was applied to resolve ballistic impact phenomena. The technique can adaptively refine a mesh in the neighborhood of a shock and coarsen the mesh for the smooth flow behind the shock according to a criterion. The criterion for refinement and coarsening is based upon the standard deviation of the gradient of shock pressure on the associated field. Shock simulation starts with the rough mesh of the pressure field and mesh density is increased locally under the criterion at each time step. The results show that the mesh adaptation enables to minimize the global computation error of FEM and to increase storage and computational saving compared to the fixed resolution of the conventional static mesh approach.

• 자동차안전학회지
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• 제14권4호
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• pp.77-83
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• 2022

Occupant behaviors and body contact with vehicle interior parts are main injury mechanism in far-side collisions. In vehicle side impact accident where the crash accident occurs on the opposite side of the vehicle from the a particular occupant, it is exposed in terms of relatively larger lateral motion to interact with the opposite side of the vehicle structure. The challenge of minimizing motions of upper body and injury risk according to a direct contact is a primary occupant protection research. This study has performed a data analysis of real-world accident database extracted from the 2016~2020 CISS database and a parametric investigation of impact angles and occupant kinematics in far-side lateral and oblique impact simulations. A detailed data analysis was conducted to reveal the relationship among the accident and injury data. Database analysis and computational far-side impact results proposed the fundamental vehicle design for safety improvement in far-side collisions.

• 한국산학기술학회논문지
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• 제21권11호
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• pp.843-850
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• 2020

본 연구의 목적은 국내 위험물 운송용 탱크화차의 충돌안전설계 가이드라인 제안을 위해 해외 충돌안전 기준에 따른 국내 위험물 운송화차에 대하여 비선형 충돌해석을 하여 위험성을 평가하고, 구조적 취약부를 분석하는데 있다. 유럽의 EN 12663-2에서 규정하는 화차의 완충시험 및 북미 49CFR179에서 규정하는 탱크 펑크시험기준을 분석하였으며, 상용 유한요소 해석 솔버인 LS-DYNA를 이용하여 각각 기준에 따른 비선형 유한요소모델을 모델링하였다. EN 규격의 완충시험 해석결과 충돌속도 6 km/h 이하에서는 소성변형이 발생하지 않을 것으로 예측하였지만, 8 km/h 이상의 충돌속도에서 중앙연결기를 통한 하중 전달으로 차체의 센터실 후방 및 탱크 중앙 지지부에서 소성변형을 확인하였다. 북미 법규의 탱크 펑크시험 해석결과 국내 탱크화차는 두부 충돌모드에서 충돌차량의 운동에너지를 4 % 이상 흡수시 두부의 코너부에서 탱크 외벽의 파괴가 발생하였으며, 측면 충돌모드에서 운동에너지 30 % 이상 흡수시에 충격체가 접촉하는 탱크 외벽의 파괴가 발생하여 내부 적재물의 누출을 예상하였다. 국내 유류 운송용 탱크화차의 해외 충돌안전 기준의 만족을 위해서는 차체 구조보강 설계 및 탱크 방호설계 수준을 향상시킬 필요가 있다.

• 자동차안전학회지
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• 제11권4호
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• pp.63-68
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• 2019

The Korean traffic systems for transportation vulnerable are still under development and their social life are limited even if the traffic environment systems are developed consistently. To secure his/her mobility right, it has been required to set up the particular system for the traffic welfare, for example the express and intercity bus operations for wheelchair users. The express and intercity bus development for wheelchair users based on the original bus model has been performed. This study has investigated the safety tolerance for the bus stiffness, rollover and side impact characteristics to ensure occupant safety using the finite element models. The wheelchair bus model showed the improved crashworthiness according to the partially reinforced structure and better safety tolerance for the wheelchair users.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.79-92
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• 2015

In this study, free vibration analyses of symmetric laminated cantilever and simply supported damaged composite beams are investigated by using finite element method (FEM). Free vibration responses of damaged beams are examined using Euler Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB software to determine the natural frequencies of a damaged beam. The local damage zone is assumed to be on the surface lamina of the beam by broken fibers after impact. The damaged zone is modeled as a unidirectional discontinuous lamina with $0^{\circ}$ orientations in this study. Fiber volume fraction ($v_f$), fiber aspect ratio ($L_f/d_f$), damage length ($L_D$) and its location (${\lambda}/L$), fiber orientation and stacking sequence parameters effects on natural frequencies are investigated. These parameters are affected the natural frequency values significantly.

• Structural Engineering and Mechanics
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• 제41권1호
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• pp.83-94
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• 2012

Assessment of a monumental concrete arch bridge with a total length of 210 meters having three major spans of 30 meters and a height of 65 meters, which is located in an earthquake-prone region in southern part of the country is presented in this study. Three-dimensional finite element model of the bridge was generated using a commercially available general finite element analysis software and based on the outcomes of a series of in-depth acceleration measurements that were conducted on-site, the model was refined. By using the structural parameters obtained from the dynamic and the static tests, calibrated model of the bridge structure was obtained and this model was used for necessary calculations regarding structural assessment and evaluation.

• 자동차안전학회지
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• 제13권4호
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• pp.99-105
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• 2021

Vehicle occupant postures are anticipated to vary more widely during automated driving and to become more significant in terms of the autonomous vehicle safety. Experimental and computational approaches are needed to investigate and evaluate occupant behaviors during automated driving in general. However the validity and effect of such occupant postures are unknown, thus it is necessary to examine occupant behaviors and injury countermeasures for various occupant postures. This study was focused on the development and evaluation of restraint system model for occupant behavior examinations in the first step according to autonomous vehicle occupant safety. The finite element models of dummy and restraint system were set up and simulation results showed overall model performance and safety tolerances of different reclined occupant postures during frontal impact loading.

• Wind and Structures
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• 제36권1호
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• pp.31-40
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• 2023

This paper investigates the mechanical behavior of full-scale offshore fish cages under hydrodynamic loads. To simulate different cases, different materials were used in the fish cage and analyzed under different flow velocities. The cage system is studied in two parts: net cage and floating collar. Analyses were performed with the ANSYS Workbench program, which allows the Finite Element Method (FEM) and Computational Fluid Dynamics (CFD) method to be used together. Firstly, the fish cage was designed, and adjusted for FSI: Fluid (Fluent) analysis. Secondly, mesh structures were created, and hydrodynamic loads acting on the cage elements were calculated. Finally, the hydrodynamic loads were transferred to the mechanical model and applied as a pressure on the geometry. In this study, the equivalent (von Mises) stress, equivalent strain, and total deformation values of cage elements under hydrodynamic loads were investigated. The data obtained from the analyses were presented as figures and tables. As a result, it has been shown that it is appropriate to use all the materials examined for the net cage and the floating collar.

• 한국가스학회지
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• 제12권1호
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• pp.1-6
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• 2008

샤피충격시험은 동적하중 하에 있는 고분자 재료의 거동을 이해하는데 가장 널리 사용되고 있는 방법이다. 본 연구에서는 샤피충격시험장치에서 얻어지는 파단에너지를 사용하여 나일론 소재 샤피 시편의 노치각도에 따른 에너지 해방율을 구하는 방법을 제시하였다. 또한 샤피충격시험장치를 계장화하여 최대 하중과 파단 시까지 소요되는 에너지 등의 파손인자들을 산출하였다. 그리고 노치각도에 따른 동적파괴 인성치와 유한요소법을 사용하여 중앙집중 하중 하에서 사피 시편의 노치각도에 따른 응력분포를 산출하였다.