• 한국군사과학기술학회지
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• 제23권5호
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• pp.485-493
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• 2020

Numerical analyses were performed using a one-dimensional Euler equation and Godunov Harten-Lax-Van Leer(HLL) Riemann solver in order to study the deceleration characteristics of a 155 mm projectile in a soft recovery system. The soft recovery system consisting of a series of pressure tubes is a system that decelerates the test projectile fired at supersonic speed using a high-pressure gas and filled water inside. Therefore, depending on the gas pressure and the amount of water filling, the deceleration and the exit velocity of the test projectile inside the pressure tube are determined. In this paper, the deceleration characteristics of the test projectile were analyzed according to the gas pressure and water mass filled.

• 한국군사과학기술학회지
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• 제24권6호
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• pp.619-628
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• 2021

In order to compare numerical analyses made by Song and Kim needed for predicting gas and water filling with experimental results we conducted an experiment to recover a test projectile (43.7 kg with a 155 mm diameter) at a velocity of 775 m/s in a soft recovery system with a length of 179 m using pressurized gas and filled water. The soft recovery system consisting of a series of pressure tubes had a diaphragm, piston, and water plug for filling the pressurized gas and water. We installed a continuous wave Doppler radar system for velocity measurements of the test projectile travelling in the pressure tubes and pressure transducers for measuring the pressure in the soft recovery system. Continuous wave Doppler radar has the advantage of achieving real-time measurements of the velocity of a test projectile. The velocity-time curve of the test projectile, measured using the continuous wave Doppler radar, and the pressure profile were compared with the numerical analysis results. The experiment results show good agreement with the numerical analysis results based on the one-dimensional Euler equation with an HLL Riemann solver.

• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1961-1971
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• 2006

A soft recovery system (SRS) is a device that stops a high speed projectile without damaging the projectile. The SRS is necessary to verify the shock resistant requirements of microelectronics and electro-optic sensors in smart munitions, where the projectiles experience over 20,000 g acceleration inside the barrel. In this study, a computer code for the performance evaluation of a SRS based on ballistic compression decelerator concept has been developed. It consists of a time accurate compressible one-dimensional Euler code with use of deforming grid and a projectile motion analysis code. The Euler code employs Roe's approximate Riemann solver with a total variation diminishing (TVD) method. A fully implicit dual time stepping method is used to advance the solution in time. In addition, the geometric conservation law (GCL) is applied to predict the solutions accurately on the deforming mesh. The equation of motion for the projectile is solved with the four-stage Runge-Kutta time integration method. A small scale SRS to catch a 20 mm bullet fired at 500 m/s within 1,600 g-limit has been designed with the proposed method.

• 한국전산구조공학회논문집
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• 제24권6호
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• pp.591-599
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• 2011

본 논문에서는 외연적 수치해석기법을 사용한 RC슬래브와 연성충격체의 충돌시뮬레이션 수행시 결과에 영향을 미칠 수 있는 영향인자들에 대한 변수연구를 수행하여 각 인자들이 해석결과에 미치는 영향을 고찰하였다. 수치시뮬레이션은 1970~1980년대에 독일에서 원자력발전소의 항공기충돌 설계와 관련하여 수행한 다수의 시험 중 하나인 Meppen test에 대하여 수행하였으며, 총 21case의 실험 중 II/4 실험의 경우를 대상으로 하였다. 수치해석에 사용한 software는 LSTC사의 LS-DYNA이며, 변수연구에서 고려한 인자로는 콘크리트와 강재의 재료모델, strain rate 효과, 지점조건의 모델링 방법 등이다. 이러한 인자들에 대한 적절한 고려를 통해 보다 정확한 시뮬레이션 결과를 얻을 수 있으며, 특히 콘크리트 재료모델의 경우 해석결과에 미치는 영향이 가장 크므로 각 모델별 특징을 사전에 인지하고 해석케이스에 적절한 재료모델을 선택하는 것이 중요할 것으로 판단된다.

• 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.

• Journal of Trauma and Injury
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• 제36권4호
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• pp.421-424
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• 2023

This case report presents the case of a 49-year-old man who presented to our level I trauma center after sustaining injuries in an altercation with local law enforcement in which he was shot with a less lethal bean bag and tased. In a primary survey, a penetrating left supraclavicular wound was noted in addition to a taser dart lodged in his flank. No other traumatic findings were noted in a secondary survey. Given hemodynamic stability, completion imaging was obtained, revealing a foreign body in the left lung, a left open clavicle fracture, a C5 tubercle fracture, a possible grade I left vertebral injury, and a left first rib fracture. Soft tissue gas was seen around the left subclavian and axillary arteries, although no definitive arterial injury was identified. The bean bag projectile was embedded in the parenchyma of the left lung on cross-sectional imaging. The patient underwent thoracotomy for removal of the projectile and hemostasis. A thoracotomy was chosen as the operative approach due to concerns about significant bleeding upon foreign body removal. A chest tube was placed and subsequently removed on postoperative day 5. The patient was discharged on postoperative day 7. At a 2-week outpatient follow-up visit, the patient was doing well. This case report is the first to describe this outcome for a drag-stabilized bean bag. Although law enforcement officers utilize bean bag projectiles as a "less lethal" means of crowd control and protection, these ballistics pose significant risk and can result in serious injury.

• 대한기계학회논문집A
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• 제39권8호
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• pp.737-742
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• 2015

탄도 수정탄은 기존의 포탄에 조종 kit를 장착하여 목표를 정밀 타격할 수 있게 하는 무기 체계이다. 롤제어시스템은 조종 kit의 구성품으로 유도조종부와 탄체부 사이에 위치하며 포발사시 횡방향으로 5,000g 상당의 가속도 하중을 받게 된다. 따라서 내고충격 설계를 하는게 중요하다. 선진국에서는 탄도 수정탄의 개발과정에서 실사격 또는 포발사 회수 시스템을 이용하여 부품의 성능 및 강도를 평가하고 있으나 많은 시간과 비용이 든다는 단점이 있다. 따라서 본 연구에서는 CAE 해석적 방법으로 설계단계에서 롤제어시스템에 대한 충격 강도 평가를 할 수 있도록 해석 모델을 개발하였다. 충격 현상을 구현하기 위하여 Explicit code를 이용한 Dynamic 해석 기법을 적용하였고, 고변형률 물성 특성을 Johnson-Cook material model을 이용하여 구현하였다. 또한 베어링을 인너, 아우터 레이스, 리테이너, 볼 등으로 상세적으로 구현하여 충격시 베어링의 거동 특성이 분석될 수 있도록 하였다. 개발된 해석 모델은 가스건 충격시험을 통해 그 신뢰성이 있음을 검증하였다.