• 화약ㆍ발파
• /
• 제22권4호
• /
• pp.7-15
• /
• 2004

본 연구에서는 PFC3D를 사용한 폭원모델링 기법을 제안하고, 제안된 기법을 시멘트 모르타르와 같은 연약재료의 발파에 적용하여 그 적용성을 시험해 보았다. PFC3D는 개별요소법(DEM)을 기반으로 하고 있어 응력파의 전파와 재료의 동적 파괴현상을 모사하는데 적합한 코드로 분류된다. 폭원모델링 과정에서는 공내입자들의 반경을 팽창/수축시키는 기법을 통해 공벽입자들에 접촉력의 형태로 폭발압력을 부여하는 방법을 사용하였으며, 입력하중에 따라 공벽에서 유발되는 접촉력을 계산단계마다 측정 및 보정함으로써 폭발압력의 크기를 제어할 수 있도록 하였다. 시멘트 모르타르 블록의 발파모델링 과정에서는 기존의 외력을 이용하는 방법과 본 연구에서 제안하고 있는 접촉력을 이용하는 기법을 각기 적용함으로써 연약재료의 파괴과정을 정성적으로 비교하여 보았다. 해석결과, 제안된 폭원모델링 기법을 적용한다면 암석이나 콘크리트와 같은 공학재료들이 발파과정에서 보이는 파괴거동을 수치적으로 보다 유사하게 모사 할 수 있을 것으로 판단된다.

• Ocean Systems Engineering
• /
• 제1권2호
• /
• pp.111-119
• /
• 2011

Mines, torpedoes and improvised explosive devices (IED) pose a serious threat to the survivability of naval combatants. Inasmuch, a major goal in the design of modern combatant ships has been to eliminate or at least reduce the devastating damage caused by underwater explosion events. Even though there has been extensive research performed on the various underwater explosion phenomena and their associated effects, effective shock testing and shock proofing strategies for naval ship systems have proven to be illusive. Through the use of modeling and simulation (M&S), live fire test and evaluation (LFT&E) and laboratory testing, general guidelines for the shock hardening of shipboard equipment and systems have been developed. In this paper, current aspect of ship survivability has been addressed and future direction is discussed.

• 한국소음진동공학회논문집
• /
• 제22권1호
• /
• pp.81-87
• /
• 2012

This paper establishes a modeling and simulation procedure for structural response and reliability of a cylindrical array sensor on submarines under the shock generated by underwater explosion. The structural reliability of SONAR is important because the submarine could get out of combat ability by the structural damage of the SONAR upon explosion. A cylindrical array sensor was first modeled using the finite element method. Modal analysis was then performed for the check of the reliability of the modeling. The shock resistance simulations were performed for the responses to the structural shock waves and for the responses to the directly applied underwater shock waves, according to BV-043 and MIL-STD-901D, respectively. The stresses of the structure were evaluated with von-Mises scheme. Vulnerable regions were exposed through mapping the maximum stress to the structural model. Maximum stress of the SONAR was compared with the yield stress of the material to examine the structural reliability.

• 화약ㆍ발파
• /
• 제23권3호
• /
• pp.27-42
• /
• 2005

본 연구에서는 $PFC^{3D}$상에서 공내입자들의 반경을 팽창/수축시키는 기법을 통해 공벽입자들에 접촉력의 형태로 폭발압력을 부여하는 폭원모델링을 기법을 소개하고, 제안된 기법을 이용하여 홉킨슨 효과 효과와 스폴링 현상을 응용하여 암석코어에 대한 응력파의 전파 및 반사과정을 기존의 외력을 적용함으로써 서로 비교하여 보았다. 암석코어는 직경 20m, 길이 200mm의 입자결합체로서 접촉결합을 이용하여 구성하였으며, 시료의 선단에 주기 0.050m$(50{\mu}s)$의 펄스형태의 폭발하중을 기존의 방법과 제안된 폭원모델링 기법을 이용하여 각기 입사시켰다. 해석결과 두 기법은 서로 유사한 결과를 보였으며, 입사압축파는 0.060ms$(60{\mu}s)$ 이후 시료의 후단에서 반사되어 반사인장파의 형태로 되돌아오면서 시료의 축방향과 직각방향으로 인장균열을 발생시켰다. 또한 시료 중을 전파하는 응력파의 속도는 4,167m/s로 계산되어 물리시료에 대한 측정치 4,300m/s와 $3\%$ 정도의 근소한 오차를 보였다.

• 화약ㆍ발파
• /
• 제42권3호
• /
• pp.1-8
• /
• 2024

발파공에서 기록된 압력-시간 이력들은 사용된 폭약의 종류에 따라 다양한 모양을 보인다. 하지만 이런 이력곡선들은 대개 상승부와 하강부로 구분할 수 있다. 이 특징은 암석발파를 모델링 할 때 폭발압력의 시간이력을 정의하는 데 도움이 될 수 있다. 그러나 Jiang의 폭압함수는 두 개의 형상변수를 가지고 있는데, 이들은 상승시간과는 명확한 관계가 있으나 하강시간과의 관계는 명시적이지 않다. 따라서 본 논문에서는 상승 및 하강시간이 주어지면 상응하는 형상변수들을 정확하게 결정할 수 있는 두 개의 변환식을 유도하였다. 그런 다음, 이 변환식들을 이용하여 여타의 폭압함수들을 Jiang의 함수로 근사하였다. 이와 같은 함수근사의 가능성은 암석발파를 모델링 할 때 폭압함수 자체보다는 물리적으로 중요한 의미를 지닌 상승 및 하강시간에 초점을 맞추도록 해준다.

• 대한조선학회논문집
• /
• 제55권3호
• /
• pp.215-221
• /
• 2018

The structural design of offshore installations against explosions has been required to protect vital areas (e.g. control room, worker's area etc.) and minimize the damage from explosion accidents. Because the explosion accident will not only result in significant casualties and economic losses, but also cause serious pollution and damage to surrounding environment and coastal marine ecosystems. Over the past two decades, an incredible efforts was made to develop reliable methods to reduce and manage the explosion risk. Among the methods Quantitative Risk Assessment and Management (QRA&M) is the one of cutting-edge technologies. The explosion risk can be quantitatively assessed by the product of explosion frequency based on probability calculation and consequence analyzed using computer simulations, namely Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA). However to obtain reliable consequence analysis results by CFD and FEA, uncertainties associate with modeling and simulation are needed to be identified and validated by comparison with experimental data. Therefore, large-scaled explosion test procedure is developed in this study. And developed test procedure can be helpful to obtain precious test data for the validation of consequence analysis using computer simulations, and subsequently allow better assessment and management of explosion risks.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제12권1호
• /
• pp.988-995
• /
• 2020

Air gun shock systems are commonly used as alternative explosion energy sources for underwater explosion (UNDEX) shock tests owing to their low cost and environmental impact. The airbag inflator of automotive airbag systems is also very useful to generate extremely rapid underwater gas release in labscale tests. To overcome the restrictions on the very small computational time step owing to the very fine fluid mesh around the nozzle hole in the explicit integration algorithm, and also the absence of a commercial solver and software for gas UNDEX of airbag inflator, an idealized airbag inflator and fluid mesh modeling technique was developed using nozzle holes of relatively large size and several small TNT charges instead of gas inside the airbag inflator. The objective of this study is to validate the results of an UNDEX response analysis of one and two idealized airbag inflators by comparison with the results of shock tests in a small water tank. This comparison was performed using the multi-material Arbitrary Lagrangian-Eulerian formulation and fluid-structure interaction algorithm. The number, size, vertical distance from the nozzle outlet, detonation velocity, and lighting times of small TNT charges were determined. Through mesh size convergence tests, the UNDEX response analysis and idealized airbag inflator modeling were validated.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.419-424
• /
• 2004

we performed the underwater explosion analysis for the liquefied oxygen tank - a kind of fuel tank of a mid-size submarine, and tried to verify the structural safety for this structure. First, we reviewed the theory and application of underwater explosion analysis using Structure-Fluid Interaction technique and its finite element modeling scheme. Next, we modeled the explosive and sea water as fluid elements, the LOX tank as structural elements and the interface between two regions as ALE scheme. The effect on shock pressure and impulse of fluid mesh size and shape are also investigated. As the analysis result, the shock pressure due explosion propagated into the water region and hit the structure region. The plastic deformation and the equivalent stress highly appeared at the web frame and the shock mount of LOX structure, but these values were acceptable for design criteria.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.220-223
• /
• 2008

A test facility to measure the performance of a KM(Kick Motor) is constructed, and prediction of blast wave propagation over the facility is performed to check if the safety of test personnel in MCC(Main Control Center) can be guaranteed even for the most severe explosion. Assuming that the initial explosion energy is contained in a sphere under the pressure of 500, 1000, 1500 psi, respectively, the radius of the sphere is determined for each pressure to set the mass of contained explosion gas to 35 kg. The material properties of explosion gas are set to be the ones of KM propellant combustion gas under normal condition. To reduce the effort and time required for a complex three-dimensional modeling, the flowfield is approximated to axismmetry. Calculations are performed for all three initial pressure conditions, and the analysis of the result is given for 1500 psi which is expected to be the worst case. The maximum pressure is 3.5 psig while the minimum pressure is -1.2 psig on the outer wall of MCC, and the maximum pressure difference between the inner and outer walls of protection wall amounts to 3.0 psi.

• 한국해양공학회지
• /
• 제19권1호
• /
• pp.20-25
• /
• 2005

The authors performed the underwater explosion analysis for the liquified oxygen tank - a kind of fuel tank of a mid-size submarine, and tried to verify the structural safety for this structure. First, the authors reviewed the theory and application of underwater explosion analysis, using a Structure-Fluid Interaction technique and its finite element modeling scheme. Next, the authors modeled the explosive and sea water as fluid elements, the LOX tank as structural elements, and the interface between the two regions as the ALE scheme. The effect on shock pressure and impulse of fluid mesh size and shape are also investigated. Upon analysis, it was found that the shock pressure due to explosion propagated into the water region, and hit the structure region. The plastic deformation and the equivalent stress were apparent at the web frame and the shock mount of LOX structure, but these values were acceptable for the design criteria.