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알루미늄 2519 판재의 충격저항성 평가에 대한 수치 해석적 연구
구만회,우호길,Koo Man-Hoi,Woo Ho-Gil 한국군사과학기술학회 2004 한국군사과학기술학회지 Vol.7 No.3
In this paper, the acceptance criteria(Striking Velocities) for the A12519 weldments have been developed. Dynamic impact simulation of A12519 plate was achieved by using LS-DYNA, and predict the projectile velocity and the crack length. Also, Ballistic impact tests of A12519 plate have been performed, and compared with analysis results. Critical velocities of A12519 plate were acquired respectively, and striking velocities of A12519 weldments were calculated. Present work data will be used by basic data in ballistic impact test for A12519 weldments.
구만회,이창현,김학인,우호길,Koo Man-Hoi,Lee Chang-Hyun,Gimm Hak-In,Woo Ho-Gil 한국군사과학기술학회 2005 한국군사과학기술학회지 Vol.8 No.1
In order to evaluate the credibility of the welded joint design for combat vehicle using A12519, the numerical analysis for the joint model has been studied and the results are compared with the experimental works by the impact projectiles. The numerical approach using LS-DYNA involves the process of the crack initiation and propagation as well as the applications of the failure criteria for both the ductile and brittle failures. The good agreement between the numerical and experimental works are proved.
선형폭발성형탄(LEFP) 충격에 의한 WHA 관통자의 관통성능 감소에 관한 수치해석 연구
주재현,최준홍,구만회,김동규,Joo, Jaehyun,Choi, Joonhong,Koo, ManHoi,Kim, Dongkyu 한국군사과학기술학회 2017 한국군사과학기술학회지 Vol.20 No.3
A linear explosively formed penetrator(LEFP) is a modification of the explosively formed penetrator(EFP). An EFP is axisymmetric and has a dish-shaped liner while LEFP has a rectangular-shaped liner with curved cross section. Upon detonating LEFP forms laterally wide projectile like blade, leaving a long penetration hole on the target. On the other hand, a long-rod tungsten heavy alloy(WHA) penetrator is one of the major threats against most of the ground armored vehicles. In this paper, the feasibility of using an LEFP in protecting against a long-rod WHA penetrator by colliding LEFP into the threat was investigated through a set of numerical simulations. In this study, a scale-down WHA penetrator with length to diameter ratio(L/D) of 10.7 and 7.0 mm diameter was used to represent a long-rod WHA penetrator. LS-DYNA and Multi-Material ALE technique were employed for the simulation. For estimation of the protection effect by LEFP, residual penetration depths into RHA by the threat were compared according to various impact locations against the threat.
주재현,김학인,구만회,박지우,Joo, Jae-Hyun,Gimm, Hak-In,Koo, Man-Hoi,Park, Jee-Woo 한국군사과학기술학회 2010 한국군사과학기술학회지 Vol.13 No.5
A numerical analysis for the space frame structure under ballistic and blast loads was performed using LS-DYNA, a commercial code. The space frame structure was developed to be adapted to the ground vehicle in the future and it was designed to build with Al7039 frames and lightweight multi-layered panels for the purpose of weight reduction and shock mitigation. The analyses have done for side impacts by a cylindrical projectile and Comp. C-4 explosive representing major threats to the vehicle. The deformed shape of the panel section and stresses as well as accelerations of the frames calculated from LS-DYNA were compared to the test results to validate the analysis model. The internal energies for panels and frames from LS-DYNA were also compared to each other to discern their role in absorbing the ballistic and blast impact.
박찬영,양홍준,이경훈,우관제,구만회,주재현,Park, Chan-Young,Yang, Hong-Jun,Lee, Kyoung-Hoon,Woo, Kwan-Je,Koo, Man-Hoi,Joo, Jae-Hyun 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.6
In this paper, the characteristics of shock behavior of multi-layered panels under impact were studied. The panels consist of four different lightweight materials including al, al-foam, rubber and FRP in order to enhance their shock energy absorption. A commercial code, Ls-dyna was used to build the numerical model and study shock behavior based on the analysis of shock response spectrum and peak response acceleration. The reliability of the numerical model was estimated by its comparison with the experimental results acquired under the same impact conditions.
복합 구조물의 충격 응답 특성을 이용한 취약성 평가 모델 연구
박정원(Jeongwon Park),구만회(Man Hoi Koo),박준홍(Junhong Park) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.10
복합 구조물의 충격 진동 특성을 이용한 취약성 분석 기법을 제안하였다. 프레임 요소로 구성된 구조물의 충격 거동을 파악하기 위해서 스펙트럴요소법을 적용하였다. 티모센코 보함수를 이용해 고속충돌에 의한 고주파 성분을 포함하는 충격파 전파 특성을 시뮬레이션하였다. 구조물의 결합부분에서는 종방향과 횡방향 파동의 상호 작용을 고려한 파동 전달을 해석하였다. 충격력이 구조물에 작용할 경우 주파수 및 시간 응답을 얻고 전체 구조물에서 충격에너지 전파 특성을 파악하였다. 구조물의 위치별로 계산된 최대가속도 크기와 시스템을 구성하는 주요 부품의 허용 가속도 기준에 의한 취약확률 함수를 정의하고 시스템의 취약 확률을 계산하였다. 제안된 취약성 분석 절차를 이용해 3 차원 전투 차량의 충격 응답을 얻고 충격에 취약한 구조물 위치를 파악하였다. This work presents a vulnerability assessment procedure for a complex structure using vibration characteristics. The structural behavior of a three-dimensional framed structure subjected to impact forces was predicted using the spectral element method. The Timoshenko beam function was applied to simulate the impact wave propagations induced by a high-velocity projectile at relatively high frequencies. The interactions at the joints were analyzed for both flexural and longitudinal wave propagations. Simulations of the impact energy transfer through the entire structure were performed using the transient displacement and acceleration responses obtained from the frequency analysis. The kill probabilities of the crucial components for an operating system were calculated as a function of the predicted acceleration amplitudes according to the acceptable vibration levels. Following the proposed vulnerability assessment procedure, the vulnerable positions of a three-dimensional combat vehicle with high possibilities of damage generation of components by impact loading were identified from the estimated vibration responses.
김종희,김건우,김철기,이승구,구만회,Kim, Jong-Hee,Kim, Kun-Woo,Kim, Cheol-Gi,Lee, Seung-Goo,Koo, Man-Hoi 한국재료학회 2012 한국재료학회지 Vol.22 No.3
Magnetic nanoparticles for ferromagnetic fluids and magnetorheological fluids were prepared by chemical coprecipitation and mechanical milling, respectively. The surface-treated particles were dispersed at various weight ratios into a medium of polyethylene glycol. In order to evaluate the elastic modulus of the fluids, ultrasonic pulse velocities were measured with an ultrasonic test using transducers of 5MHz and 2.25MHz. The ultrasonic signals were only available with a transducer of 2.25 MHz at fluid concentrations of 5 mg/ml and lower. In the case of applying transducers over 2.25 MHz and concentrations over 5 mg/ml to the fluids, it was impossible to observe effective ultrasonic signals due to an excessive scattering of the pulses by the dispersed particles. Elastic moduli of the magnetorheological fluids were 5.44 GPa and 6.13 GPa with concentrations of 25 mg/ml and 50 mg/ml, respectively; these values were higher by 40% than the values of 4.04 GPa and 4.28 GPa of ferromagnetic fluids at the same concentrations. As for the effect of an external magnetic field on these dilute fluids, the ultrasonic signals were positioned in a very similar way, which was probably due to insufficient arrangement of the particles even though the reflection energy of the ultrasonic waves apparently increased.
충격에 의한 구조물의 진동 응답을 이용한 멀티스케일 취약성 평가 시뮬레이션
박정원(Jeongwon Park),구만회(Man Hoi Koo),박준홍(Junhong Park) 제어로봇시스템학회 2012 제어로봇시스템학회 합동학술대회 논문집 Vol.2012 No.7
Vibration resulting from high velocity projectile impact to a structure was simulated on multiple scales. Local impact simulations were performed to predict material deformation and penetration phenomena at the impacted location. Resulting penetration behavior of steel panel was analyzed with various projectile velocity. The forces acting on the panel in the transverse directions were calculated from the obtained stress distribution in the local deformation model. Using the estimated force, transient flexural wave propagations were obtained to analyze the radiation of impacted energy along the structural span. Consequently, vulnerable positions with high possibility of damage generation on crucial components by impact loading were identified from the resulting vibration responses.