• Structural Engineering and Mechanics
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• 제40권5호
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• pp.617-636
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• 2011

We present the numerical implementation, simulation, and validation of the high-velocity impact experiments that have been described in the companion article. In this part, numerical investigations and simulations performed to mimic the tests are presented. The experiments were analyzed by the explicit integration-based software ABAQUS for improved simulations. Targets were modeled with a damaged plasticity model for concrete. Computational results of residual velocity and crater dimensions yielded acceptable results.

• 한국전산구조공학회논문집
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• 제24권6호
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• pp.591-599
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• 2011

본 논문에서는 외연적 수치해석기법을 사용한 RC슬래브와 연성충격체의 충돌시뮬레이션 수행시 결과에 영향을 미칠 수 있는 영향인자들에 대한 변수연구를 수행하여 각 인자들이 해석결과에 미치는 영향을 고찰하였다. 수치시뮬레이션은 1970~1980년대에 독일에서 원자력발전소의 항공기충돌 설계와 관련하여 수행한 다수의 시험 중 하나인 Meppen test에 대하여 수행하였으며, 총 21case의 실험 중 II/4 실험의 경우를 대상으로 하였다. 수치해석에 사용한 software는 LSTC사의 LS-DYNA이며, 변수연구에서 고려한 인자로는 콘크리트와 강재의 재료모델, strain rate 효과, 지점조건의 모델링 방법 등이다. 이러한 인자들에 대한 적절한 고려를 통해 보다 정확한 시뮬레이션 결과를 얻을 수 있으며, 특히 콘크리트 재료모델의 경우 해석결과에 미치는 영향이 가장 크므로 각 모델별 특징을 사전에 인지하고 해석케이스에 적절한 재료모델을 선택하는 것이 중요할 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제77권3호
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• pp.329-342
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• 2021

In this paper, the effect of different steel bar configurations on the quasi-static punching and impact response of concrete slabs was studied. A total of forty RC square slab specimens were cast in two groups of concrete strengths of 40 and 63 MPa. In each group of twenty specimens, ten specimens were reinforced at the back face (singly reinforced), and the remaining specimens were reinforced on both faces of the slab (doubly reinforced). Two rebar spacing of 25 and 100 mm, with constant reinforcement ratio and effective depth, were used in both singly and doubly reinforced slab specimens. The specimens were tested against the normal impact of cylindrical projectiles of hemispherical nose shape. Slabs were also quasi-statically tested in punching using the same projectile, which was employed for the impact testing. The experimental response illustrates that 25 mm spaced rebars are effective in (i) decreasing the local damage and overall penetration depth, (ii) increasing the absorption of impact energy, and (iii) enhancing the ballistic limit of RC slabs. The ballistic limit was predicted using the quasi-static punching test results of slab specimens showing a strong correlation between the dynamic perforation energy and the energy required for quasi-static perforation of slabs.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.95-99
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• 2004

본 연구에서는 충돌문제에 있어서 비교적 높은 활용도를 지니고 있는 범용 유한요소해석코드 LS-DYNA3D를 사용해 판부재에 충돌체가 충돌하는 경우, 내충돌성을 평가하였다. 속도가 41.56m／s-118.9m／s로 비교적 고속인 충돌문제부터 속도가 544.05m／s-800m／s인 초고속 충돌문제까지 시리즈 해석을 하였다. 이를 통해 판부재에 다양한 속도의 충돌체가 충돌하는 경우에 있어 피충돌체의 관통 유무를 평가할 수 있는 경험식을 구하고자 한다.

• Composites Research
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• 제25권6호
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• pp.191-197
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• 2012

본 연구에서는 수치적 시뮬레이션을 통해 탄소/에폭시 복합재 적층판의 고속충돌 관통 거동을 연구하였다. 해석은 상용유한요소 해석프로그램인 LS-DYNA를 사용하여 해석을 수행하였고, 적층판 및 구형 강철 충격체 모두 3차원 요소로 모델링 하였다. 해석에는 적층순서가 $[45/0/-45/90]_{ns}$인 16 및 24장으로 된 복합재 적층판을 고려하였으며 충격체의 초기속도는 140-250 m/s 범위의 값을 사용하였다. 해석결과 예측된 잔류속도는 실험값과 비교적 잘 일치하였다.

• 대한조선학회논문집
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• 제54권4호
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• pp.286-293
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• 2017

This paper presents ballistic limit velocity results of a variety of materials generally used in warships. Ballistic limit velocity is the velocity required for a projectile to penetrate a target with 50 percents of time and is widely used as a measure of armour bulletproofing. For this study, live fire experiments were implemented using AK-47 $7.62{\times}9mm$ mild steel core as a projectile as well as various thickness warship materials as a target. Also, methods of MIL-STD-662F, NIJ-STD-0101.06 and support vector machine were applied to measure the ballistic limit velocity and then their results were graphically analyzed for comparison. The minimum of their results was considered as the ballistic limit velocity in a conservative way.

• Steel and Composite Structures
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• 제47권3호
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• pp.395-403
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• 2023

The main objective of this article is to investigate the response of different fiber metal laminates subjected to low velocity impact experimentally and numerically via finite element method (FEM). Hence, two different fiber metal laminate (FML) samples (GLARE/CARALL) are made of 7075-T6 aluminum sheets and polymeric composites reinforced by E-glass/carbon fibers. In order to study the responses to the low velocity impacts, samples are tested by drop weight machine. The projectiles are released from 1- and 1.5-meters height were the speed reaches to 4.42 and5.42 meter per second and the impact energies are measured as 6.7 and 10 Joules. In addition to experimental study, finite element simulation is done and results are compared. Finally, a detailed study on the maximum deflection, delamination and damages in laminates and geometry's effect of projectiles on the laminate response is done. Results show that maximum deflection caused by spherical projectile for GLARE samples is more apparent in comparison with the CARALL samples. Moreover, the maximum deflection of GLARE samples subjected to spherical projectile with 6.7 Joules impact energy, 127% increases in comparison with the CARALL samples in spite of different total thickness.

• 한국건설순환자원학회논문집
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• 제8권3호
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• pp.349-355
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• 2020

이 연구의 목적은 섬유의 혼입량과 종류에 따른 고강도 섬유보강 복합재료의 정적하중에서의 압축강도 및 인장거동과 비상체 하중 하에서의 충격 저항성을 조사하고자 한다. 이를 위하여 3가지 배합을 설계하였고, 압축강도, 직접인장, 그리고 고속 비상체 충돌 실험을 수행하였다. 실험결과 섬유의 혼입량은 압축강도에 비하여 인장강도에 큰 영향을 미치며, 하이브리드 섬유 사용으로 인장변형성능이 향상되는 것으로 나타났다. 강섬유의 혼입량은 충격 저항성에 큰 영향을 미치는 것으로 나타났다. 하이브리드 섬유를 사용하면 충격 저항성이 더욱 향상되는 것으로 나타났다. 다만, 단일 섬유 사용에 비하여 실험체별성능 차이가 크게 발생하는 것으로 나타났다.

• Steel and Composite Structures
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• 재36권6호
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• pp.703-710
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• 2020

This paper presents numerical and theoretical investigations on the strain rate in steel-concrete composite (SC) panels under low-velocity impact of a hemispherical rigid body. Finite element analyses were performed on five specimens with different loading rates. The impact energy was kept constant to eliminate its influence by simultaneously altering the velocity and mass of the projectile. Results show that the strain rate in most parts of the specimens was low and its influence on bearing capacity and energy dissipation was limited in an average sense of space and time. Therefore, the strain rate effect can be ignored for the analyses of global deformation. However, the strain rate effect should be considered in local contact problems. Equations of the local strain and strain rate were theoretically derived.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.38-39
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• 2013

In this study, in regard to fiber reinforced mortar mixing steel fiber and 4types of organic fiber, impact test was carried out. Because to predict fracture reduction performance with flexural, tensile strength when types of fiber were different as impact reduction performance of concrete is closely related with toughness such as flexural strength, tensile strength and fracture energy etc. As a result, enhancement of toughness by fiber reinforcement controls the spall of rear. On the other hand in case of steel fiber relatively turned up high toughness in appropriate load compared with organic fiber but in same mixing rate, impact reduction performance by projectile showed low performance due to few number of an individual of mixing.