• Computers and Concrete
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• v.31 no.6
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• pp.561-570
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• 2023

In this paper, the structural performance of RC and HPFRCC slabs exposed to a TNT explosion were numerically investigated. A finite element model was established using the MM-ALE method in the LS-DYNA program to simulate a near-ground TNT explosion at a scaled distance of 1.08 m/kg³. The K&C model was calibrated to exactly reflect the material properties of HPFRCCs that were developed in KICT and KNU. Numerical and experimental results were compared for the damage distribution and failure shape of the slabs. Based on the verified numerical model, a parametric study was carried out to demonstrate the effects of compressive strength and thickness of the slab on the blast resistance. In particular, the spallation failure on the back side of the slab is greatly dependent on the thickness. Finally, additional numerical simulations were conducted to explore the variation in blast pressure characteristics according to the scaled distance and explosive shape. It was confirmed that the pressure induced by cubic TNT was more destructive to the slab than cylindrical and spherical TNT in a nearfield explosion.

• Explosives and Blasting
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• v.39 no.1
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• pp.1-9
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• 2021

As the national economic growth and the rapid increase in industrial structures are aging, the demand for removing steel structures is increasing, and research on improving the penetration performance of the linear shape charge explosives. In the study, numerical analyses were performed on the effect of the type of explosive used in the self-made shape charging container and the initiation method on the cutting performance of the steel plate and the effect on the shaped explosive installed close to it. ANSYS LS-DYNA, which can analyze the large deformation problem of materials due to explosion, was used, and an ALE(Arbitrary-Lagrange-Eulerian) model was applied that enables interlocking analysis of gases, liquids, and solid.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.181-186
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• 2006

In this paper, generation mechanisms of ocean freak waves are briefly introduced in the context of wave-current interaction phenomena. The present model of the fluid motion is based on the Navier-Stokes equations incorporating velocity-pressure formulation because of need to model the nonlinear wave interaction with spatially non-uniform current field. In order to deal with the free surface motion, an Arbitrary Lagrangian-Eulerian (ALE) description is adopted. As an accurate and efficient numerical tool, the spectral element method is presented with general features and specific treatment for the wave-current interaction problem. As an intermediate stage of development, solution procedure and characteristics aspects of the present modeling and numerical method are addressed in detail, and preliminary numerical results prove its accuracy and convergence.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.1
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• pp.55-62
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• 2015

The electromagnetic force induced by an intense electric current pulse, which generates an electromagnetic field around the metal jet originating from a shaped charge, can disperse and scatter the high-speed metal jet. An electric device consisting of an RLC circuit applies an intense electric current pulse that flows in the circuit while the metal jet passes between two electrodes. In this study, the metal jet formation was simulated using the ALE technique in 2-D, and a 3-D finite element model was mapped using 2-D simulation results to induce the electric current directly. The deformed shapes of the metal jet and the electromagnetic force were calculated using a finite element analysis by inducing the electric current directly, and the major parameters of the intense electric current pulse for breaking up the metal jet were examined.

• Structural Engineering and Mechanics
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• v.53 no.3
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• pp.393-410
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• 2015

Two dimensional numerical models and physical models have been developed to study the highly nonlinear interactions between waves and breakwaters, but several of these models consider the effects of the structural dynamic responses and the shape of the breakwater axis on the wave pressures. In this study, a multi-material Arbitrary Lagrangian Eulerian (ALE) method is developed to simulate the nonlinear interactions between nonlinear waves and elastic seawalls on a coastal rubble mound breakwater, and is validated experimentally. In the experiment, a solitary wave is generated and used with a physical breakwater model. The wave impact is validated computationally using a breakwater - flume coupling model that replicates the physical model. The computational results, including those for the wave pressure and the water-on-deck, are in good agreement with the experimental results. A local breakwater model is used to discuss the effects of the structural dynamic response and different design parameters of the breakwater on wave loads, together with pressure distribution up the seawall. A large-scale breakwater model is used to numerically study the large-scale wave impact problem and the horizontal distribution of the wave pressures on the seawalls.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.286-290
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• 2008

This paper summarizes the components of an explicit aeroelastic solver developed especially for the simulation of dynamic fracture events occurring during the flight of solid propellant rockets. The numerical method combines an explicit Arbitrary Lagrangian Eulerian (ALE) version of the Cohesive Volumetric Finite Element (CVFE) scheme, used to simulate the spontaneous motion of one or more cracks propagating dynamically through a domain with regressing boundaries, and an explicit unstructured finite volume Euler code to follow the flow field during the failure event. A key feature of the algorithm is the ability to adaptively repair and expand the fluid mesh to handle the large geometrical changes associated with grain deformation and crack motion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.47-54
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• 2006

In this paper, numerical algorithms applied in two-step eulerian scheme are investigated and implemented. Element quantities are advected with donor or van Leer algorithm. Nodal quantities are advected with Simplifed ALE [SALE] algorithm. Material interfaces are determined with Simple Line Interface Calculation [SLIC] algorithm. Practical aspects considered for code development are addressed in detail. The results of developed two-step Eulerian code are verified by comparing with those from pure lagrangian scheme and commercial code.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.19-21
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• 2005

EPCglobal은 RFID와 관련된 다양한 분야의 표준화를 주도하고 있으며 응용 표준으로써 Tag 정보의 운용을 위한 미들웨어 표준인 ALE Specification을 제시하였다. ALE의 ECSpec은 애플리케이션이 미들웨어에 등록하는 이벤트 필터링을 위한 스펙으로써 일정 시간동안 반복적으로 수행되는 연속 질의와 유사한 특성을 가진다. ECSpec을 연속질의로 변환할 때 해당질의의 WHERE절이 가지는 Predicate는 매우 긴 길이를 가지는 Long Interval이 된다. 이러한 특성은 기존의 질의 색인들의 삽입과 검색 성능을 저하시키는 문제점을 가진다. 이 논문에서는 ECSpec을 연속 질의의 형태로 변환하고 해당 질의가 기지는 Predicate인 2D Interval의 특성을 반영한 새로운 질의 색인 구조로써 TLC-Index를 제안한다. 색인 구조는 그리드 방식의 큰 크기를 가지는 셀 분할 구조와 선분 모양의 가상 분할 구조를 병행하는 하이브리드 구조이다. 색인에서 Long Interval의 정의는 셀 분할 구조의 길이보다. 크거나 같은 길이를 가지는 interval이다. 제안하는 색인은 Long Interval을 큰 크기를 가지는 셀 분할 구조로 분할 삽입함으로써 저장 공간의 소모를 줄이고 삽입 성능을 향상시킨다. 또한 Short Interval들을 짧은 길이를 가지는 가상 분할 구조들로 분할 삽입함으로써 그리드 방식이 가질 수 있는 부분적 겹침을 제거하여 검색 성능을 향상시킨다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.235-237
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• 2008

A unified hydrocode, ExLO, in which Largrangian, ALE and Eulerian solvers are incorporated into a single framework, has recently been developed in Korea. It is based on the three dimensional explicit finite element method and written in C++. ExLO is mainly designed for the calculation of structural responses to highly transient loading conditions, such as high-speed impacts, high-speed machining, high speed forming and explosions. In this paper the numerical schemes are described. Some improvements of the material interface and advection scheme are included. Details and issues of the momentum advection scheme are provided. In this paper the modeling capability of ExLO has been described for two extreme loading events; high-speed impacts and explosions. Numerical predictions are in good agreement with the existing experimental data. Specific applications of the code are discussed in a separate paper in this journal. Eventually ExLO will be providing an optimum simulation environment to engineering problems including the fluid-structure interaction problems, since it allows regions of a problem to be modeled with Lagrangian, ALE or Eulerian schemes in a single framework.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.185-191
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• 1996

The Variation of die bearing is primary way to control the metal flow in hot square die extrusion process. Finite element computations are carried out to assess the influence of die bearing on metal flow and state variables. The finit element method is developed based on ALE description for a rigid-viscoplastic material. Since thermal state computational example, hot square die extrusion with varied die bearing lengths has been analyzed for the profile of a L-section.