• Journal of the Korea Institute of Military Science and Technology
• /
• v.20 no.3
• /
• pp.384-392
• /
• 2017

A linear explosively formed penetrator(LEFP) is a modification of the explosively formed penetrator(EFP). An EFP is axisymmetric and has a dish-shaped liner while LEFP has a rectangular-shaped liner with curved cross section. Upon detonating LEFP forms laterally wide projectile like blade, leaving a long penetration hole on the target. On the other hand, a long-rod tungsten heavy alloy(WHA) penetrator is one of the major threats against most of the ground armored vehicles. In this paper, the feasibility of using an LEFP in protecting against a long-rod WHA penetrator by colliding LEFP into the threat was investigated through a set of numerical simulations. In this study, a scale-down WHA penetrator with length to diameter ratio(L/D) of 10.7 and 7.0 mm diameter was used to represent a long-rod WHA penetrator. LS-DYNA and Multi-Material ALE technique were employed for the simulation. For estimation of the protection effect by LEFP, residual penetration depths into RHA by the threat were compared according to various impact locations against the threat.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.11
• /
• pp.983-989
• /
• 2007

The bird strike simulation is a problem characterized by a high degree of uncertainty. It deals with nonlinear dynamics, complicated models of bird materials and geometry, as well as a plenty of possible boundary and initial conditions. In this complex field, uncertainty management plays an important role. This paper aims to assess the effect of input uncertainty of bird strike analysis on the impact behavior of the leading edge of the WIG(Wing in Ground Effect) craft obtained with finite element analysis using LS-DYNA 3D. The uncertainties of the bird strike simulation arise due to imprecision or lack of information, due to variability or scatter, or as a consequence of model simplification. These uncertain parameters are represented by fuzzy numbers with their membership functions quantifying an initial guess for the actual value of the model parameter. Using the transformation method as a special implementation of fuzzy arithmetic, the model can be analyzed with the intention of determining the influence of each uncertain parameter on the overall bird strike behavior.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.2A
• /
• pp.117-122
• /
• 2012

Coastal structures, constructed for preventing coastal slope erosion, often causes the scour on the boundary between the coastal structure and the sea-bed, which might lead to collapse of coastal structures. To prevent the collapse, the usual upright block type coastal structures can be modified to other forms or systems of coastal structures. To validate the performance of the proposed systems, it is necessary to conduct high cost hydraulic experiments. If numerical modeling can be performed prior to the hydraulic experiments and the performance of the proposed systems is analyzed numerically in advance, the expenses can be reduced significantly by optimizing the number of cases for conducting the experiments. In this study, a fluid-structure interaction analysis procedure is proposed for modeling the hydraulic experiments of costal structures using the finite element package, LS-DYNA. As can be found in the usual hydraulic experiments, fluid velocities of potential scour locations are monitored and analyzed in detail for four types of coastal structures, block, step, trapezoid and rubble mound.

• Composites Research
• /
• v.28 no.2
• /
• pp.58-64
• /
• 2015

The purpose of this paper is to suggest the effective equivalent finite element model for the impact limiter of a nuclear spent fuel shipping cask made of sandwich composite panels. The sandwich composite panels were composed of a metallic facesheet and a core material made of urethane foam, balsa wood and red wood, respectively. The effective equivalent finite element model for the impact limiter was proposed by comparing the results of low-velocity impact test of sandwich panels. An explicit finite element analysis based on LS-DYNA 3D was done in this study. The results showed that the solid elements were recommended to model the facesheet and core of sandwich panels for impact limiter compared to combination modeling method, in which the layered shell element for facesheet and solid element for core material are used. In particular, the solid element for balsa and red wood core materials should be modeled by the element elimination approach.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.5
• /
• pp.110-116
• /
• 2003

With the growth of aircraft performance and needs for light aircraft, the problems associated with hail impacts on aircraft during flights and grounding become and important issue. These hail encounters can cause severe damages to aircraft and result in major concerns in safety and cost. Since nearly all external components of the commercial and military aircraft-in particular, the nose section and the leading edge of the wing and tail-are subject to damages, much effort has been put into understanding of this problem. However, most of the previous studies have focused on the composite components and few results have been reported for the metallic components. In this paper, we study the ice impacts on the aluminum component with the finite element analysis method utilizing commercial non-linear dynamics solver LS-DYNA. The results are compared with the experimental data and a simple measure of the ice impact effects is proposed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.3
• /
• pp.233-239
• /
• 2017

The CA (Control Assembly) of an SFR has a CRA(Control Rod Assembly) with an inner duct and control rod. During an emergency situation, the CRA falls into the duct of the CA for a rapid shut-down. The drop time and impact velocity of the CRA are important parameters with respect to the reactivity insertion time and the structural integrity of the CRA. The objective of this study was to investigate the dynamic behavior and integrity of the CRA owing to a drop impact. The impact analysis of the CRA under normal/abnormal drop conditions was carried out using the commercial FEM code LS-DYNA. Results of the drop impact analysis demonstrated that the CRA maintained structural integrity, and could be safely inserted into the flow hole of the damper under abnormal conditions.

• Journal of Korean Society of Steel Construction
• /
• v.28 no.2
• /
• pp.65-74
• /
• 2016

A finite element dynamic simulation is performed to gain an insight about the stiffened blast wall structures subjected to blast loading. The simulation was verified using qualitative and quantitative comparisons for different materials. Based on in-depth examination of blast simulation recordings, dynamic behaviors occurred in the blast wall against the explosion are determined. Subsequent simulation results present that the blast wall made of the high performance steel performs much better in the shock absorption. In this paper, the existing finite element shock analysis using the LS-DYNA program is further extended to study the dynamic response of the stiffened blast wall made of the high-performance steel considering high strain-rate effects. The numerical results for various parameters were verified by comparing different material models with dynamic effects occurred in the stiffened blast wall from the explosive simulation.

• Journal of the Society of Naval Architects of Korea
• /
• v.49 no.6
• /
• pp.521-527
• /
• 2012

It is well known that flexible composite material propeller has superior radiation noise characteristics with outstanding damping effects. In this paper, three flexible composite material propellers were produced using compression molding process, and their hydrodynamic performances and radiation noise characteristics were measured. One propeller, C1, was made up from carbon/epoxy composite laminates, and the other two ones, G1 and G2, from glass/epoxy ones. Their fiber arrays were selected by the progressive damage structural analysis of propellers using composite material model MAT_162 (Composite_DMG_MSC) linked with LS-DYNA code. Carbon/epoxy and glass/epoxy composite specimen tests were performed, their damage mechanisms were figured out, and their parameters were calibrated by their progressive damage structural analysis according to their damage criteria.

• Journal of the Korean Society for Railway
• /
• v.13 no.3
• /
• pp.271-277
• /
• 2010

In this paper, a numerical model for a Kevlar/Epoxy and Carbon-Kevlar/Epoxy tube used as an energy absorbing component has been developed and then results have been verified through experiment. The 2D shell element and Chang-Chang failure criterion of LS-DYNA that is commercial explicit FE code was used. Mechanical material properties for the model were obtained by material testing in advance. The numerical results were compared with quasi-static test results under axial compressive loading at 10mm/min. From the results, in the case of the Kevlar/Epoxy tube, load-crushed displacement curves were very close to the experiments and SEA (specific energy absorption) shows a good agreement with experimental one within less than 6%. However, the Carbon-Kevlar/Epoxy tube shows some differences with the experimental results.

• Journal of the Korea Society for Simulation
• /
• v.29 no.2
• /
• pp.119-127
• /
• 2020

This study numerically investigated a structural behavior subjected to consecutive explosions. To this end, a small scale one-way reinforced slab (RC) with fixed-fixed boundary condition was considered as the target structure, and a commercial software, LS-DYNA, was utilized for finite element (FE) analysis. Prior to performing FE analysis, preliminary tests were carried out to verification of a computational model for the one-way RC slab. In the numerical simulation, identical blast loads were consecutively applied to the structure, and cumulative damage assessment were carried out based on its maximum dynamic displacements. As a result of the numerical simulation, it was found that maximum displacements considering permanent deformation due to a prior explosion were almost linearly increased in every explosion until the hazardous damage threshold.