• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.114-122
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• 2000

Bullet impact tests for solid rocket motor were performed and its results wert described. Two motors were made of composite and steel for case material, respectively and their reactions to the bullet impact were compared. Throughout the tests it had been tried to setup the procedure of bullet impact test and criteria of the judgment for the reactions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.163-166
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• 2009

Bullet and fragment impact test with rocket motors was performed and characteristics of the results were analyzed. The material of the motor case was carbon epoxy composite. The motor was loaded with HTPE propellants to improve the insensitive munitions characteristics. In the tests, sound pressure and heat flux sensors were used to determine the category of response according to the standard. The reaction response of all of the HTPE motors impacted by bullet and fragment was judged as Type V burning.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.3
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• pp.281-288
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• 2016

The ballistic performance data of composite materials is distributed due to material inhomogeneity. In this paper, the uncertainty in residual velocity is obtained experimentally, and a method of predicting it is established numerically for the high-speed impact of a bullet into laminated composites. First, the failure strain distribution was obtained by conducting a tensile test using 10 specimens. Next, a ballistic impact test was carried out for the impact of a fragment-simulating projectile (FSP) bullet with 4ply ([0/90]s) and 8ply ([0/90/0/90]s) glass fiber reinforced plastic (GFRP) plates. Eighteen shots were made at the same impact velocity and the residual velocities were obtained. Finally, simulations were conducted to predict the residual velocities by using the failure strain distributions that were obtained from the tensile test. For this simulation, two impact velocities were chosen at 411.7m/s (4ply) and 592.5m/s (8ply). The simulation results show that the predicted residual velocities are in close agreement with test results. Additionally, the modeling of a composite plate with layered solid elements requires less calculation time than modeling with solid elements.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.1
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• pp.30-38
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• 2002

Bullet impact tests for two solid rocket motors were performed and its results were compared and analyzed. One was loaded with the existing propellant with decreased weight content of burning rate catalyst and added high density additives to improve mechanical properties and the other was loaded with the existing propellant with decreased weight content of burning rate catalyst to improve its insensitivity as well as to maintain the ballistic performance. The composite cases were used for both motors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2553-2558
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• 2014

Military rotorcraft should be designed taking into account the condition of the fuel cell bullet impact. The internal fluid pressure, stress of metal fitting and fuel cell, bullet kinetic energy can be included as the design factor for the fuel cell. The best way to obtain the important design data is to conduct the verification test with actual product. But, the verification test requires huge cost and long-term effort. Moreover, there is high risk to fail because of the sever test condition. Thus, the numerical simulation is required to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact simulation based on SPH(smoothed particle hydrodynamics) is conducted with the commercial package, LS-DYNA. As the result of the numerical simulation, the internal pressure of fuel cell is calculated as 350~360MPa and the equivalent stress caused by hydro-ram effect is predicted as 260~350MPa on metal fittings.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.71-78
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• 2014

There is a big risk of bullet impact because military rotorcraft is run in the battle environment. Due to the bullet impact, the rapid increase of the internal pressure can cause the internal explosion or fire of fuel cell. It can be a deadly damage on the survivability of crews. Then, fuel cell of military rotorcraft should be designed taking into account the extreme situation. As the design factor of fuel cell, the internal fluid pressure, structural stress and bullet kinetic energy can be considered. The verification test by real object is the best way to obtain these design data. But, it is a big burden due to huge cost and long-term preparation efforts and the failure of verification test can result in serious delay of a entire development plan. Thus, at the early design stage, the various numerical simulations test is needed to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact numerical simulation based on SPH(smoothed particle hydrodynamic) is conducted with the commercial package, LS-DYNA. Then, the resulting equivalent stress, internal pressure and bullet's kinetic energy are evaluated in detail to examine the possibility to obtain the configuration design data of the fuel cell.

• Journal of Sensor Science and Technology
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• v.28 no.5
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• pp.318-322
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• 2019

In shooting training, an impact point identification system that uses the impact wave of the bullet to check the impact point in the target plate has been recently used. Acoustic sensors used in these systems must be able to detect shock waves of high sound pressure levels and be both waterproof and dustproof for rainy weather and dusty environments, respectively. In this study, membranes with excellent waterproof, dustproof, and sound transmitting characteristics were selected through a characteristics test; a protection cap was installed to install the selected materials. After coupling the produced protection cap to the acoustic sensor housing, the sensitivity and phase characteristics of the acoustic sensor were checked. Through the waterproof and dustproof test, the performances of its sensitivity and phase characteristics were confirmed. Finally, the normal shockwave of a 5.56 mm diameter bullet was measured using a shockwave detection signal collecting plate equipped with a prototype of the acoustic sensor at a 100 m firing range.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.4
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• pp.630-638
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• 2011

A new smooth bore test barrel was developed to be used in sensitivity assessment test for explosives and fragment impact test. The bore diameter of the barrel is 20 mm, and the powder chamber is designed to be replaceable with the 12.7 mm, 20 mm and 30 mm type chamber. The test results showed the wide range of fragment velocity from 400 to 2000 m/s, included the fragment velocity requirement of the fragment impact test(alternate procedure #1) in MIL-STD-2105B. The stability of the bullet trajectory was checked by test shots and the structural safety of the system has been confirmed through the stress analysis and the interior ballistics analysis of the barrel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.29-29
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• 1998

실전 배치되어 운용 중인 무기체계는 여러 형태의 사고 위험이 항상 존재한다 이중에서도 특히 항공기나 함정에서 발생하는 사고는 그 피해가 막대하게 커질 수도 있어 항공기나 함정 자체에 위협을 줄 수도 있다. 이러한 사고위험으로부터 인적, 물적 자원을 보호하기 위하여 둔감탄약(Insensitive Munitions)에 대한 인식이 높아지고 있으며, 아울러 이러한 무기 체계를 효과적으로 시험 평가하는 규격들이 검토되기 시작하여 1991년에 "Hazards Assesment Tests for Non-Nuclear Ordnance, DoD-STD-2105"를 기초로 한 MIL-STD-2105B가 채택되었다. 본 논문에서는 MIL-STD-2105B의 해석과 그에 따른 둔감탄약 시험에 포함되는 Bullet Impact Test, Fast Cookoff Test, Slow Cookoff Test, Fragment Impact Test, Sympathetic Detonation Test 등의 시험들의 세부적인 시험방법과 그 결과에 대한 판정 기준을 서술하였다. 또한 유도무기의 추진기관을 모델로 하여 둔감탄약 시험의 기준을 제시하였고 이 시험을 통과하기 위하여 향후 연구, 개발하여야 할 분야를 서술하였다.

• Composites Research
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• v.24 no.6
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• pp.7-11
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• 2011

Polyurethane oligomers (PUOs) such as UA8297, UP127 and EB8200 were utilized to enhance the anti-bullet property of Dyneema$^{(R)}$/vinylester composites. First, prepregs of PUO and vinylester (XSR10) were prepared via spray coating on Dyneema$^{(R)}$ fabric at 21 % resin content (by volume). In addition, spray coating and film lamination were also carried out with a mixture of XSR10/PUO for selected PUOs. Next, the prepregs were dried at RT for 1-2 h and then at $100^{\circ}C$ for 30 min to remove the solvent and to provide partial cure when necessary. The prepregs were stacked in 24 layers and cured at $120^{\circ}C$ for 5 min under the contact pressure and for additional 25 min at 150 $kg/cm^2$. Finally, the anti-bullet properties of composite samples were evaluated by measuring $V_{50}$ with simulated fragment projectile (SFP, 17 gr). The results showed a 6.5 and 9.0 % increase of $V_{50}$ with UP127 and EB8200, respectively.