• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.236-244
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• 2017

In this study, the high-velocity impact penetration behavior of $[45/0/-45/90]_{ns}$ carbon/epoxy composite laminates was studied. The considered configuration includes a spherical steel ball impacting clamped circular laminates with various thicknesses and diameters. First, the impact experiment was performed to measure residual velocity and extent of damage. Next, the impact experiment was numerically simulated through finite element analysis using LS-dyna. Three-dimensional solid elements were used to model each ply of the laminates discretely, and progressive material failure was modeled using MAT162. The result indicated that the finite element simulation yielded residual velocities and damage modes well-matched with those obtained from the experiment. It was found that fiber damage was localized near the impactor penetration path, while matrix and delamination damage were much more spread out with the damage mode showing a dependency on the orientation angles and ply locations. The ballistic-limit velocities obtained by fitting the residual velocities increased almost linearly versus the laminate diameter, but the amount of increase was small, showing that the impact energy was absorbed mostly by the localized impact damage and that the influence of the laminate size was not significant at high-velocity impact.

• Journal of Korea Foundry Society
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• v.33 no.2
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• pp.63-68
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• 2013

Generally, metal is the most important material used in many engineering applications. Therefore, it is important to understand and predict the damage of metal as result of the impact. The objective of this research is to evaluate the damage criterion on the impact performance of A356 Al-alloy castings. Both experimental method and computational analysis were used to achieve the research objective. In this paper, we performed impact test according to various impact velocities to the A356 cast aluminium specimen for damage prediction. Impact computational simulation was done by applying properties obtained from the tensile test, and damages was predicted according to the damage criteria based plastic work. The good agreement of the results between the experiment and computer simulation shows that the reliability of the proposed FE simulation method to predict fracture of A356 casting components by impact.

• Transactions of Materials Processing
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• v.24 no.2
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• pp.130-137
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• 2015

This paper presents the development process of automotive side door impact beam for passenger cars. Weight reduction while maintaining functional requirements is one of the major goals in the automotive industry. In this study, thin-walled side door beam using quenchable boron steel was designed to reduce the weight of conventional side door tubular one. In order to estimate design for the proposed side door beams, the static side impact protection tests(FMVSS 214) were conducted using the finite element method. Based on the simulation results, geometry modification of the side door beam has been performed via creating new reinforcing ribs. Furthermore, the manufactured frontal impact beam was mounted on the real side door of a passenger car, and then static impact protection test carried out. It is concluded that the presented test results can provide significant contribution to the stiffness of side door impact beams and light-weighting door research.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.883-890
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• 1992

Analysis of dynamic or impact problems is very important in engineering fields such as airplanes and automobiles. In the present study, two-dimensional elastodynamic BEM program with Laplace transformation is developed to analyze dynamic or impact problems. Accuracy and efficiency of the BEM program are tested by making the comparision of impact analysis of some models with other's published results. The BEM developed is applied to the impact crack problem and the dynamic stress intensity factors of some impact cracks is obtained by the displacement extrapolation method. It is confirmed to be possible to analyze impact problems accurately with only a little elements in simple models. And also it is found to be careful to use the singular element usually using in static crack problems because that the elastodynamic fundamental solution usually using in static crack problems because that the elastodynamic fundamental solution has more sensitive singularity than the static fundamental solution and to determine the boundary conditions in dynamic problems.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.498-503
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• 2004

A fundamental function of court sport shoes has been considered as the protection of human feet from unexpected injuries. But, recently its role for improving the playing competency is being regarded as a more important function. In connection with this situation, intensive efforts are being world-widely forced on the development of court sport shoes proving the excellent playing competency, by taking kinesiology and biomechanics into consideration. However, the success of this goal depends definitely on the shoes design based upon the reliable evaluation of shoes functional parts. This paper addresses the application of finite element method to the evaluation of landing impact force of court sport shoes. In order to reflect the coupling effect between leg and shoes accurately and effectively, we construct a fully coupled shoes-leg FEM model which does not rely on the independent experimental data any more. Through the numerical experiments, we assess the reliability of the coupled FEM model by comparing with the experimental results and investigate the landing impact characteristics of court sport shoes.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.706-711
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• 2007

Numerical studies were performed to examine the effects of notch location of impact specimens on the failure behavior of HAZ (heat affected zone) when Charpy V-notch impact test were made at a low temperature ($1^{\circ}C$). Carbon steel plate (SA-516 Gr. 70) with thickness of 25mm for pressure vessel was welded by SMAW (shielded metal-arc welding) and specimens were fabricated from the welded plate. Charpy tests were then performed with specimens having different notch positions of specimens varying from the fusion line through HAZ to base metal. A series of finite element analysis which simulates the Charpy test and crack propagation initiating at the tip of V-notch was carried out as well. The finite element analysis takes into account the irregular fusion line and non-homogenous material properties due to the notch location of the specimen in HAZ. Results reveals that the energies absorbed during impact test depend significantly on the notch location and direction of specimen. Finite element analysis also demonstrates that the notch location of specimens, to a great extent, influences the reliability and consistency of the test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1589-1597
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• 1997

The high-velocity impact forging process with eccentric loading condition is analyzed using the explicit time integration finite element method. In order to consider the strain hardening, strain rate hardening and thermal softening effects, which are frequently observed in high-velocity deformation phenomena, the Johnson-Cook constitutive model is applied to model the workpiece. It is assumed that the material response of the dies is elastic in the study. As a result of the eccentric loading simulation, it is found that the increase of the eccentric ratio and the allowable tilting angle cause the decrease of the maximum forging load and the blow efficiency, and it is also found that the forging load and the blow efficiency generated in the high-velocity impact forging process with three-dimensional geometry can be obtained efficiently.

• Advances in concrete construction
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• v.1 no.4
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• pp.289-304
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• 2013

A reliable concrete constitutive material model is critical for an accurate numerical analysis simulation of reinforced concrete structures under extreme dynamic loadings including impact or blast. However, the formulation of concrete material model is challenging and entails numerous input parameters that must be obtained through experimentation. This paper presents a damage scale analytical model to characterize concrete material for its pre- and post-peak behavior. To formulate the damage scale model, statistical regression and finite element analysis models were developed leveraging twenty existing experimental data sets on concrete compressive strength. Subsequently, the proposed damage scale analytical model was implemented in the finite element analysis simulation of a reinforced concrete pier subjected to vehicle impact loading and the response were compared to available field test data to validate its accuracy. Field test and FEA results were in good agreement. The proposed analytical model was able to reliably predict the concrete behavior including its post-peak softening in the descending branch of the stress-strain curve. The proposed model also resulted in drastic reduction of number of input parameters required for LS-DYNA concrete material models.

• Structural Engineering and Mechanics
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• v.58 no.5
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• pp.799-823
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• 2016

A finite element model for the non-linear dynamic analysis of a reinforced concrete (RC) containment shell of a nuclear power plant subjected to extreme loads such as impact and earthquake is presented in this work. The impact is modeled by using an uncoupled approach in which a load function is applied at the impact zone. The earthquake load is modeled by prescribing ground accelerations at the base of the structure. The nuclear containment is discretized spatially by using 20-node brick finite elements. The concrete in compression is modeled by using a modified $Dr{\ddot{u}}cker$-Prager elasto-plastic constitutive law where strain rate effects are considered. Cracking of concrete is modeled by using a smeared cracking approach where the tension-stiffening effect is included via a strain-softening rule. A model based on fracture mechanics, using the concept of constant fracture energy release, is used to relate the strain softening effect to the element size in order to guaranty mesh independency in the numerical prediction. The reinforcing bars are represented by incorporated membrane elements with a von Mises elasto-plastic law. Two benchmarks are used to verify the numerical implementation of the present model. Results are presented graphically in terms of displacement histories and cracking patterns. Finally, the influence of the shear transfer model used for cracked concrete as well as the effect due to a base slab incorporation in the numerical modeling are analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1786-1793
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• 2004

A fundamental function of court sport shoes was considered as the protection of human feet from unexpected injuries. But, recently its role for improving the playing competency has been regarded as of more importance. In connection of this situation, intensive efforts are world-widely forced on the development of court sport shoes proving the excellent playing competency by taking kinesiology and biomechanics into consideration. However, the success of this goal depends definitely on the shoes design based upon the reliable evaluation of shoes functional parts. This paper addresses the application of finite element method to the evaluation of landing impact force of court sport shoes. In order to reflect the coupling effect between leg and shoes accurately and effectively, we construct a fully coupled shoes-leg FEM model which does not rely on the independent experimental data any more. Through the numerical experiments, we assess the reliability of the coupled FEM model by comparing with the experimental results and investigate the landing impact characteristics of court sport shoes.