• Advances in concrete construction
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• 제12권5호
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• pp.391-398
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• 2021

This paper presents an experimental study exploring impact resistant properties of Kagome truss reinforced composite panels. Three types of panels with different materials and reinforcements, i.e., ultra-high-performance mortar, steel fiber, and Kagome truss, were designed and manufactured. High-velocity projectile impact tests were performed to investigate the impact response of panels with dimensions of 200 mm×200 mm×40 mm. The projectile used in the testing was a steel slug with a hemispherical front; the impact energy was 1 557 J. Test results showed that the Kagome truss reinforcement was effective at improving the impact resistance of panels in terms of failure patterns, damaged area, and mass loss. Synergy effects of a combination of Kagome truss and fiber reinforcements for the improvement of impact resistance capacity of ultra-high-performance mortar were also observed.

• 한국구조물진단유지관리공학회 논문집
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• 제15권4호
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• pp.155-164
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• 2011

충격 하중 재하 실험의 경우 빠른 하중 재하 속도로 인해 실험 데이터를 측정하는 방법에 있어 많은 어려움이 있다. 또한 부재의 국부적 손상을 측정하지 못함으로써 부재의 동적 거동을 왜곡하는 문제점이 존재한다. 따라서, 본 연구에서는 충격 실험에서의 한계를 극복하기 위하여 명시적(explicit) 유한요소 해석 프로그램인 LS-DYNA를 이용하여 FRP Sheet 및 강섬유로 보강된 콘크리트의 저속 충격 하중 하에서의 동적 거동을 분석하였다. 해석 모델은 1방향 및 2방향 부재이며 충격 하중 재하 시부재의 국부적 파괴를 고려하고 있다. 해석결과 강섬유에 의해 보강된 SFRC와 UHPC 부재의 경우 충격 저항성능이 크게 향상되었다. FRP Sheet로 보강한 경우 GFRP가 CFRP보다 우수한 충격 저항 성능을 보였으며 FRP Sheet의 방향성에 의한 영향은 크게 나타나지 않았다. 본 연구에서 수행된 해석은 충격 실험 결과와의 비교를 통해 그 신뢰성이 검증되었다.

• 한국철도학회논문집
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• 제16권5호
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• pp.365-371
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• 2013

철도차량 전면창유리 충격 시험 및 특성 파악을 위해 유럽 및 국내의 전면창유리 충격 시험 방법을 비교 검토하였다. EN 15152에 따른 고속철도차량의 전면창유리 충격 시험이 가능한 정도인 약 500km/h 속도로 충돌체를 발사할 수 있는 압축 공기식 충격 실험 발사 장치를 설계 및 제작하였으며, 이 발사장치의 충돌체 발사 성능 확인을 위해 속도 보정 실험을 실시하여 압축 공기에 따른 충돌체의 발사 속도 관계식을 도출하였다. 도시철도 및 일반철도에 사용되는 동일한 사양의 전면창유리 시편($1000mm{\times}700mm$)에 제작한 발사 장치를 이용해 충돌 시험을 수행하여 충돌 속도에 따른 시편의 충격 특성을 살펴보았다.

• Architectural research
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• 제18권4호
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• pp.179-184
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• 2016

The structure must be periodically checked and measures must be taken to prevent deterioration in building construction. From this point of view, a nondestructive test is essential to estimate whether the construction of buildings is proper, and whether the dimension of depositing concrete is consistent and without damage. This study estimated the thickness of the concrete component of construction framework using the ultrasonic velocity method and the impact echo method, in order to investigate reliability of the estimation of the thickness of normal strength concrete and high strength concrete, leading to the following conclusions. In the estimation of the thickness of the concrete structures, specimens of normal strength of 24MPa and specimens of high strength of 40MPa demonstrated an average error rate of 5.1% and 2.2%, respectively. The impact-echo method, one of the non-destructive tests, is verified as an efficient diagnostic technique. With this information, we will determine specific standards for the maintenance of structures, and the re-creation of lost building blueprints.

• International Journal of Aeronautical and Space Sciences
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• 제11권3호
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• pp.221-226
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• 2010

The failure of a Kevlar29/Phenolic composite plate under high-velocity impact from an fragment simulation projectile was investigated using the nonlinear explicit finite element code, LS-DYNA. The composite laminate and the impactor were idealized by solid elements, and the interface between the laminas was modeled as a tiebreak type in LS-DYNA. The interaction between the impactor and laminate was simulated using a surface-to-surface eroding contact algorithm. When the stress level meets the given failure criteria, the layer in the element is eroded. Numerical results were verified through existing test results and showed good agreement.

• Composites Research
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• 제22권2호
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• pp.18-23
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• 2009

비선형 동적해석 유한요소 프로그램인 LS-DYNA를 이용하여 속 파편모의탄 충돌에 의한 Kevlar29/Phenolic 복합재 평판의 파손특성을 해석하였다. 적층판과 충격체는 고체요소를 사용하여 이상화하였고, 복합재 층과 층 사이 파손 해석을 위해서는 타이드 브레이크(tied-brake)요소를 사용하였다. 충격체와 복합재 적층판은 면-대-면 소멸 접촉 알고리즘을 사용하였다. 충격체에 의한 파손과 충격체의 관통을 모사하기 위해 응력이 일정한 파손기준식을 만족하면 해당되는 요소의 해당층은 제거된다. 해석 결과는 기존의 시험 결과와의 비교를 통해 검증한다.

• 한국군사과학기술학회지
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• 제16권4호
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• pp.430-434
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• 2013

In this paper, we have investigated deformation of cup for EFI detonator in high velocity impact test. The experimental result shows that STS cup deformed 0.170 mm with the bulged shape. The numerical simulation result with static/dynamic material properties of SUS304 shows 0.166 mm of deformation. The main parameters to decrease the deformation of cup are stength, thickness and density of cup. The initial condition of SUS304 cup was strength of 215 MPa and thickness of 0.12 mm. As strength increases to 500 MPa, deformation of cup converges to 0 mm, and as thickness increases to 0.18 mm, deformation of cup converges to 0 mm. If the density of cup decreases from 8 to 2.7 g/cc, the deformation of cup decreases to 0.141 mm.

• Steel and Composite Structures
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• 제17권4호
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• pp.387-403
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• 2014

This paper presents a high accuracy Finite Element approach for delamination modelling in laminated composite structures. This approach uses multi-layered shell element and cohesive zone modelling to handle the mechanical properties and damages characteristics of a laminated composite plate under low velocity impact. Both intralaminar and interlaminar failure modes, which are usually observed in laminated composite materials under impact loading, were addressed. The detail of modelling, energy absorption mechanisms, and comparison of simulation results with experimental test data were discussed in detail. The presented approach was applied for various models and simulation time was found remarkably inexpensive. In addition, the results were found to be in good agreement with the corresponding results of experimental data. Considering simulation time and results accuracy, this approach addresses an efficient technique for delamination modelling, and it could be followed by other researchers for damage analysis of laminated composite material structures subjected to dynamic impact loading.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.505-517
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• 2016

The structural integrity of a dual-purpose metal cask currently under development by the Korea Radioactive Waste Agency (KORAD) was evaluated, through numerical simulations and a model test, under high-speed missile impact reflecting targeted aircraft crash conditions. The impact conditions were carefully chosen through a survey on accident cases and recommendations from literature. In the impact scenario, a missile flying horizontally hits the top side of the cask, which is freestanding on a concrete pad, with a velocity of 150 m/s. A simplified missile simulating a commercial aircraft engine was designed from an impact loade-time function available in literature. In the analyses, the dynamic behavior of the metal cask and the integrity of the containment boundary were assessed. The simulation results were compared with the test results for a 1:3 scale model. Although the dynamic behavior of the cask in the model test did not match exactly with the prediction from the numerical simulation, other structural responses, such as the acceleration and strain history during the impact, showed very good agreement. Moreover, the containment function of the cask survived the missile impact as expected from the numerical simulation. Thus, the procedure and methodology adopted in the structural numerical analyses were successfully validated.

• 대한기계학회논문집A
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• 제23권11호
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• pp.1886-1895
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• 1999

The delamination behavior of multidirectional carbon-fiber/epoxy composite laminates under 10NA intermediate and high rates of test, up to rate of about 11.4m s has been investigated using the double cantilever beam specimens. The mode I loading under rates above l.0m/s showed considerable dynamic effects on the load-time curves and thus higher values of the average crack velocity than that expected from a simple proportional relationship with the test rate. The modified beam analysis utilizing only the opening displacement and crack length exhibited an effective means for evaluating the dynamic fracture energy $G_{IC}$. Based on the assumption of constant flexural modulus, values of $G_{IC}$ at the crack initiation and arrest were decreased with an increase of the test rate up to 5.7m/s, but the maximum $G_{IC}$ was increased at 11.4m/s.