• Advanced Composite Materials
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• v.18 no.1
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• pp.1-20
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• 2009

This paper describes the results of experiments and numerical simulation studies on the impact and indentation damage created by low-velocity impact subjected onto honeycomb sandwich panels for application to the BIMODAL tram. The test panels were subjected to low-velocity impact loading using an instrumented testing machine at six energy levels. Contact force histories as a function of time were evaluated and compared. The extent of the damage and depth of the permanent indentation was measured quantitatively using a 3-dimensional scanner. An explicit finite element analysis based on LS-DYNA3D was focused on the introduction of a material damage model and numerical simulation of low-velocity impact responses on honeycomb sandwich panels. Extensive material testing was conducted to determine the input parameters for the metallic and composite face-sheet materials and the effective equivalent damage model for the orthotropic honeycomb core material. Good agreement was obtained between numerical and experimental results; in particular, the numerical simulation was able to predict impact damage area and the depth of indentation of honeycomb sandwich composite panels created by the impact loading.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.409-418
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• 2019

Debris flows occur in mountainous areas due to heavy rains resulting from climate change and result in disasters in the downstream area. The purpose of this study is to estimate the impact force of a debris flow when a check dam according is installed in various locations in the channel of a highly mountainous area. A Finite Differential Element Method (FDM) model was used to simulate the erosion and deposition based on the equation for the mass conservation and momentum conservation while considering the continuity of the fluid. The peak impact force from the debris flow occurred at 0 to 5 sec and 15 to 20 sec. When the supplied water discharge was increased, greater peak impact force was generated at 16 to 19 sec. This means that when increasing the water supply, the velocity of the debris flow became faster, which results in increased energy of the consolidation between the particles of the water and the sediment made. If a number of check dams were to be set up, it would be necessary to investigate the impact force at each location of the check dam. The results of this study could provide useful information in predicting the impact force of the debris flow and in installing the check dams in appropriate locations.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.419-424
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• 2012

This paper presents a tubular reciprocating translational motion permanent magnet synchronous motor for percussive drilling applications for offshore oil & gas industry. The motor model and rock model are built up by doing force analysis of the motor and analyzing the physical procesof impact. The optimization of input voltage waveforms to maximize the rate of penetration is done by simulations. The simulation results show that the motor can be utilized in percussive drilling applications and achieve a very large impact force. Simulation results for optimization also show that second harmonic input voltage produces a higher rate of penetration than the sine wave and fourth harmonic input voltages.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.3
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• pp.367-375
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• 2018

The present paper considers the contact between energy-saving device of ice-class vessel and ice block. The main objective of this study is to clarify the tendency of the ice impact force and the structural response as well as interaction effects of them. The contact analysis is performed by using LS-DYNA finite element code. The main collision scenario is based on Finnish-Swedish ice class rules and a stern duct model is used as an energy-saving device. For the contact force, two modelling approaches are adopted. One is dynamic indentation model of ice block based on the pressure-area curve. The other is numerical material modelling by LS-DYNA. The authors investigated the sensitivity of the structural response against the ice contact pressure, the interaction effect between structure and ice block, and the influence of eccentric collision. The results of these simulations are presented and discussed with respect to structural safety.

• Journal of Environmental Impact Assessment
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• v.5 no.2
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• pp.79-91
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• 1996

In Chapter 40, "Information for decision-making", of Agenda 21, it was Slated that, "indicators of sustainable development need to be developed to provide solid bases for decision-making at all levels and to contribute to a self-regulating sustainability of integrated environment and development systems." Sustainable development has been defined as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs", An indicator that measures sustainability should therefore focus on this definition. One of the most widely used frameworks for environmental indicators is the Pressure-State-Response model proposed by the OECD. And we introduced the the Driving force-State-Response framework, the adaptation of Pressure-State-Response model, for UN sustainable development indicators. Therefore, in our country, indicators for sustainable development should be developed by using the DSR framework.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1698-1708
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• 2002

The main topic covered in this paper is that of the impact process, that is, where two bodies come into contact and rebound or stick together. This paper presents how to determine the rebound velocities of a microparticle that approaches a surface with arbitrary initial velocities and relate the impact process to the physical properties of the materials and to the adhesion force. Actual adhesion forces demonstrate a significant amount of energy dissipation in the form of hysteresis, and act generally in a normal to the contact surfaces. Microparticles must also contend with forces tangent to the contact surfaces, namely Coulomb dry friction. The developed model has an algebraic form based on the principle of impulse and momentum and hypothesis of energy dissipation. Finally, several analyses are carried out in order to estimate impact parameters and the developed analytical model is validated using experimental results.

• Structural Engineering and Mechanics
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• v.60 no.5
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• pp.829-849
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• 2016

In this paper, experimental as well as numerical analysis of Glass Fiber Reinforced Polymer (GFRP) laminated composite has been presented under ballistic impact with varying projectile nose shapes (conical, ogival and spherical) and incidence velocities. The experimental impact tests on GFRP composite plate reinforced with woven glass fiber ($0^{\circ}/90^{\circ}$)s are performed by using pneumatic gun. A three dimensional finite element model is developed in AUTODYN hydro code to validate the experimental results and to study the ballistic perforation characteristic of the target with different parametric variations. The influence of projectile nose shapes, plate thickness and incidence velocity on the variation of residual velocity, ballistic limit, contact force-time histories, energy absorption, damage pattern and damage area in the composite target have been studied. The material characterization of GFRP composite is carried out as required for the progressive damage analysis of composite. The numerical results from the present FE model in terms of residual velocity, absorbed energy, damage pattern and damage area are having close agreement with the results from the experimental impact tests.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.9 s.240
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• pp.1191-1198
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• 2005

This paper is concerned with the numerical investigation of the landing impact characteristics of sport shoes to the landing mode. In most court sport activities, jumping and landing are fundamental motions, and the landing motion is largely composed of forefoot and rearfoot landing modes. Since the landing impact may, but frequently, lead to unexpected injuries of players, the investigation of its characteristics and the sport shoes design for reducing it are of a great importance. To investigate the landing impact characteristics to the landing mode, we construct a shoes-leg coupled model and carry out the numerical simulation by an explicit finite element method.

• Steel and Composite Structures
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• v.17 no.2
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• pp.159-172
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• 2014

A finite element model with the consideration of damage initiation and evolution has been developed for the analysis of the dynamic response of a composite sandwich panel subject to low velocity impact. Typical damage modes including fiber breakage, matrix crushing and cracking, delamination and core crushing are considered in this model. Strain-based Hashin failure criteria with stiffness degradation mechanism are used in predicting the initiation and evolution of intra-laminar damage modes by self-developed VUMAT subroutine. Zero-thickness cohesive elements are adopted along the interface regions between the facesheets and the foam core to simulate the initiation and propagation of delamination. A crushable foam core model with volumetric hardening rule is used to simulate the mechanical behavior of foam core material at the plastic state. The time history curves of contact force and the core collapse area are obtained. They all show a good correlation with the experimental data.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.14 no.2
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• pp.149-156
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• 2016

The spent fuel stored in the pool is vulnerable to external impacts, since the severe reactor conditions degrade the structural integrity of the fuel. Therefore an accident during shipping and handling should be considered. In an extreme case, the fuel assembly drop can be happened accidentally during handling the nuclear fuel in the spent fuel pool. The rod failure during such drop accident can be evaluated by calculating the impact force acting on the fuel assembly at the bottom of the spent fuel pool. The impact force can be evaluated with the impact velocity at the bottom of the spent fuel pool. Since fuel rods occupies most of weight and volume of a nuclear fuel assembly, the information of the rods are important to estimate the hydraulic resistance force. In this study, the hydraulic force acting on the $3{\times}3$ short rod bundle model during the drop accident is calculated, and the result is verified by comparing the numerical simulations. The methodology suggested by this study is expected to be useful for evaluating the integrity of the spent fuel.