• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3745-3765
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• 2022

The concrete structures related to nuclear safety are threatened by accidental impact loadings, mainly including the low-velocity drop-weight impact (e.g., spent fuel cask and assembly, etc. with the velocity less than 20 m/s) and high-speed projectile impact (e.g., steel pipe, valve, turbine bucket, etc. with the velocity higher than 20 m/s), while the existing studies are still limited in the impact resistant design of nuclear power plant (NPP), especially the primary RC slab. This paper aims to propose the numerical simulation and theoretical approaches to assist the impact-resistant design of RC slab in NPP. Firstly, the continuous surface cap (CSC) model parameters for concrete with the compressive strength of 20-70 MPa are fully calibrated and verified, and the refined numerical simulation approach is proposed. Secondly, the two-degree freedom (TDOF) model with considering the mutual effect of flexural and shear resistance of RC slab are developed. Furthermore, based on the low-velocity drop hammer tests and high-speed soft/hard projectile impact tests on RC slabs, the adopted numerical simulation and TDOF model approaches are fully validated by the flexural and punching shear damage, deflection, and impact force time-histories of RC slabs. Finally, as for the two low-velocity impact scenarios, the design procedure of RC slab based on TDOF model is validated and recommended. Meanwhile, as for the four actual high-speed impact scenarios, the impact-resistant design specification in Chinese code NB/T 20012-2019 is evaluated, the over conservation of which is found, and the proposed numerical approach is recommended. The present work could beneficially guide the impact-resistant design and safety assessment of NPPs against the accidental impact loadings.

• International Journal of Ocean System Engineering
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• 제2권2호
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• pp.92-96
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• 2012

This study presents a rockfall impact analysis of a typical roadway. Dynamic finite element analyses using ANSYS AUTODYN are conducted to determine the effect of the drop heights (5 m, 10 m) on the damage to a roadway model. The Rockfall is modeled as a spherical shape with a weight of 400 kg, and each drop height is converted to a corresponding impact velocity to save computational time. The roadway model is comprised of an asphalt layer, base layer, sub-base layer, and sub-grade layer. In this paper, the asphalt is modeled using a linear elastic model. The base layer, sub-base layer, and sub-grade layer are modeled using a Mohr-Coulomb model. From the analyses, the effects of the drop height on the damages and stresses are examined and discussed.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.78-85
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• 2002

This paper deals with the finite element model of the monitor for the simulation of directional free drop tests such as backward, sideward, edge and vertex drop. The model was made for an unconditional stable solution for the explicit integration algorithm. The general behaviors at the time of impact were found to well correlate with the actual situation in terms of acceleration, displacement, contact force and stress of monitor components even though the experiment of the associated drop is performed for the validity of the model.

• 방사성폐기물학회지
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• 제20권2호
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• pp.133-149
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• 2022

The design of a wooden impact limiter equipped to a transportation cask for radioactive materials was optimized. According to International Atomic Energy Agency Safety Standards, 9 m drop tests should be performed on the transportation cask to evaluate its structural integrity in a hypothetical accident condition. For impact resistance, the size of the impact limiter should be properly determined for the impact limiter to absorb the impact energy and reduce the impact force. Therefore, the design parameters of the impact limiter were optimized to obtain a feasible optimal design. The design feasibility criteria were investigated, and several objectives were defined to obtain various design solutions. Furthermore, a probabilistic approach was introduced considering the uncertainties included in an engineering system. The uncertainty of material properties was assumed to be a random variable, and the probabilistic feasibility, based on the stochastic approach, was evaluated using reliability. Monte Carlo simulation was used to calculate the reliability to ensure a proper safety margin under the influence of uncertainties. The proposed methodology can provide a useful approach for the preliminary design of the impact limiter prior to the detailed design stage.

• 한국항공운항학회:학술대회논문집
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• 한국항공운항학회 2007년도 추계학술대회
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• pp.93-96
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• 2007

• Computers and Concrete
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• 제3권2_3호
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• pp.79-90
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• 2006

This paper describes the results of an investigation into high mass-low velocity impact behaviour of reinforced concrete beams. Tests have been conducted on fifteen 2.7 m or 1.5 m span beams under drop-weight loads. A high-speed video camera has been used at rates of up to 4,500 frames per second in order to record the crack formation, propagation, particle spallation and scabbing. In some tests the strain in the reinforcement has been recorded using "Durham" strain gauged bars, a technique developed by Scott and Marchand (2000) in which the strain gauges are embedded in the bars, so that the strains in the reinforcement can be recorded without affecting the bond between the concrete and the reinforcement. The impact force acting on the beams has been measured using a load cell placed within the impactor. A high-speed data logging system has been used to record the impact load, strains, accelerations, etc., so that time histories can be obtained. This research has led to the development of computational techniques based on combined continuum/discontinuum methods (finite/discrete element methods) to permit the simulation of impact loaded reinforced concrete beams. The implementation has been within the software package ELFEN (2004). Beams, similar to those tested, have been analysed using ELFEN a good agreement has been obtained for both the load-time histories and the crack patterns.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2682-2695
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• 2021

This paper aims to evaluate the structural dynamic responses and damage/failure of the nuclear fuel reprocessing plant under the free drop impact of spent fuel cask (SFC) and fuel assembly (FA) during the on-site transportation. At the present Part I of this paper, the large-scale SFC model free drop test and the corresponding numerical simulations are performed. Firstly, a composite target which is composed of the protective structure, i.e., a thin RC plate (representing the inverted U-shaped slab in the loading shaft) and/or an autoclaved aerated concrete (AAC) blocks sacrificial layer, as well as a thick RC plate (representing the bottom slab in the loading shaft) is designed and fabricated. Then, based on the large dropping tower, the free drop test of large-scale SFC model with the mass of 3 t is carried out from the height of 7 m-11 m. It indicates that the bottom slab in the loading shaft could not resist the free drop impact of SFC. The composite protective structure can effectively reduce the damage and vibrations of the bottom slab, and the inverted U-shaped slab could relieve the damage of the AAC blocks layer dramatically. Furthermore, based on the finite element (FE) program LS-DYNA, the corresponding refined numerical simulations are performed. By comparing the experimental and numerical damage and vibration accelerations of the composite structures, the present adopted numerical algorithms, constitutive models and parameters are validated, which will be applied in the further assessment of drop impact effects of full-scale SFC and FA on prototype nuclear fuel reprocessing plant in the next Part II of this paper.

• Steel and Composite Structures
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• 제47권3호
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• pp.395-403
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• 2023

The main objective of this article is to investigate the response of different fiber metal laminates subjected to low velocity impact experimentally and numerically via finite element method (FEM). Hence, two different fiber metal laminate (FML) samples (GLARE/CARALL) are made of 7075-T6 aluminum sheets and polymeric composites reinforced by E-glass/carbon fibers. In order to study the responses to the low velocity impacts, samples are tested by drop weight machine. The projectiles are released from 1- and 1.5-meters height were the speed reaches to 4.42 and5.42 meter per second and the impact energies are measured as 6.7 and 10 Joules. In addition to experimental study, finite element simulation is done and results are compared. Finally, a detailed study on the maximum deflection, delamination and damages in laminates and geometry's effect of projectiles on the laminate response is done. Results show that maximum deflection caused by spherical projectile for GLARE samples is more apparent in comparison with the CARALL samples. Moreover, the maximum deflection of GLARE samples subjected to spherical projectile with 6.7 Joules impact energy, 127% increases in comparison with the CARALL samples in spite of different total thickness.

• 한국정밀공학회지
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• 제24권10호
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• pp.99-108
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• 2007

As the structure of a mobile phone becomes thin to catch up with a slim product trend, the reliability of a LCD module is on the rise as a big issue for a product design. A drop test is the most basic and important verification method for a mechanical quality control but it requires much time and cost during a product development process. Thus many manufacturers have considered design guide lines using CAE and simulation for more effective usage of limited resources on the market. In this paper, the Maximum Principle Stress of a LCD glass panel is calculated on the basis of explicit FE Analyses method and input conditions are determined according to the general test standard. The design guideline for reliability improvements are suggested on the basis of the results of FE Analysis.

• 대한기계학회논문집A
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• 제34권11호
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• pp.1733-1740
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• 2010

대형 드럼세탁기의 낙하 충격에 대한 포장재의 동적 거동 분석을 수행하였다. 해석에는 충격 해석에 널리 쓰이고 있는 LS-DYNA를 사용하였으며, 자유 낙하 시의 충격 가속도와 유효 응력, 그리고 고속 카메라를 통한 포장재 압축 변형 비교를 통해 해석 결과의 신뢰성을 검증하였다. 완충 특성 및 포장재 구조 에 대한 파라미터 분석을 통해 기존 포장 구조에 대한 설계 개선안을 도출하였으며, 유통 시험을 통해 유효성을 검증하였다. 본 연구에서 사용한 해석 기법 및 분석 방법 등을 통해, 향후 드럼 세탁기의 완충 성능 및 재료비 개선에 효과적으로 기여할 수 있을 것으로 기대된다.