SPH에 가상일 원리를 적용한 탄성 접촉 알고리즘

서송원(Seo Songwon),민옥기(Min Oakkey) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

There is few research about contact problem in SPH because it is primarily suitable to analyze the large deformation problem. However, an elasto-plastic problem with small deformation need to be considered about contact characteristics. The numerical formulating methods for SPH is induced to be able to abtain solutions based on a varitional method in contact problem. The contact algorithm presented is applied to the elastic impact problem in ID and 2D. The results show that an imaginary tension and a numercal instability which happen in inpacting between different materials can be removed and contact forces which could not have been calculated are able to obtain.

SPH에서 경계 조건의 적용

서송원(Songwon Seo),민옥기(Oakkey Min) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.9

SPH is an appealing and valuable computational tool using no background mesh, especially for high deformation events such as impact. But, although research has widely done since invented in 1977, this method still have several problems-lacking consistency, tensile instability and especially boundary condition treatment. This paper review current works for the method of imposing boundary conditions and test several model to certify a validity of its methods. It is compared a method using a ghost particle with that using a boundary condition about a symmetric model. Numerical tests are shown a reasonable result when impose a traction or velocity constraint to the models by equations of boundary constraint condition.

SPH에서 임의 형상의 강체면에 대한 탄소성 접촉 해석

서송원(Songwon Seo),이재훈(Jaehoon Lee),민옥기(Oakkey Min) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

There is few research about contact problem for a rigid surface with an arbitrary shape in SPH. The variational equation based on the virtual work principle is derived and its solution is obtained by the penalty method. It is proposed a new method that can determine the parameters for a penetration and a penetration rate used in the penalty method. The reproducing condition is adopted to correct the deficiency of kernel on the boundary. In order to calculate a penetration of particles, after checking boundary particles for deformable body boundary normal vectors were determined on the rigid surface. Numerical simulations for models which have rigid surface with an arbitrary shape were conducted to validate the proposed method in 2D. The results of those analysis represent that the contact algorithm proposed in this study works properly.

SPH 기법을 이용한 고속충돌을 받는 복합 적층판의 해석

이재훈(Jaehoon Lee),서송원(Songwon Seo),이인규(Ingyu Lee),민옥기(Oakkey Min) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

This paper reports experimental results and numerical simulations of high velocity impact on laminated composite plates reinforced with graphite/epoxy. To describe material behavior under high velocity impacts, a 3-D anisotropic elasto-plasticity constitutive model, an equation of state and a failure criterion for unidirectional composites have been used. The above physics were incorporated into the SPH. The numerical simulation was carried out for a steel projectile striking to laminated graphite/epoxy composite plate targets with different layup configurations. Good correlation between numerical simulation and experimental results was achieved, both in terms of deformation and damage of the laminates.

SPH 기법을 이용한 복합 적층판의 초고속 충돌 해석

이재훈(Jaehoon Lee),서송원(Songwon Seo),민옥기(Oakkey Min) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

This paper is concerned with numerical simulation of hypervelocity impacts(HVIs) of a projectile on laminated composite plate targets using SPH method. A one-parameter visco-plasticity model and damage model is used to describe the HVIs response of composite materials. The numerical simulation was carried out for a steel projectile striking to aluminum plate targets and for an aluminum projectile striking to laminated graphite/epoxy (Gr/Ep) composite plate targets. Through the numerical simulation, comparison with the HVIs response of isotropic materials and composite materials is discussed.

유도포탄 저속 회전 시 안정성 분석

김영주(Youngjoo Kim),방효충(Hyochoong Bang),서송원(Songwon Seo),박장호(Chang-Ho Pak),김진원(Jin-Won Kim),서일원(Ilwon Seo) 한국항공우주학회 2018 韓國航空宇宙學會誌 Vol.46 No.9

본 논문에서는 비선형 모델 시뮬레이션을 통해 저속 회전 중인 유도포탄의 비행 모습을 확인하고 외란으로써 여러 가지 방향과 크기의 돌풍을 작용하여 유도포탄의 비행 안정성을 분석한 방법과 결과를 소개한다. 돌풍은 3m/s, 7m/s, 10m/s, 15m/s 네 가지의 속력을 가지고 26가지의 방향에서 탄도 정점 부근부터 작용하도록 설정하였다. 초당 1회전 및 3회전으로 회전하는 경우에 대해 총 208회의 시뮬레이션을 수행한 결과를 분석하였다. 초당 3회전으로 회전할 때는 탄체가 전복되지 않았지만, 초당 1회전으로 회전할 때는 7m/s 이상의 돌풍이 작용할 때 비행 후반부에 탄체가 전복되는 경우가 발견되었다. 탄체 비행 방향 반대쪽으로 작용하여 비행 방향 대기속도를 증가하는 돌풍은 해로운 영향을 주지 않았다. 탄체전복은 모두 탄체가 하강하는 후반부에 발생하였으며, 탄도 정점 부근에서는 자세가 크게 진동하거나 탄체가 전복되지 않았다. This paper presents methods and results of nonlinear simulations for a guided munition for verifying stability at slow spin. The munition is launched by an artillery and it deploys the rear fins to reduce its spin. While the spin speed command is set to 1 rps and 3 rps, wind gusts of 3m/s, 7m/s, 10m/s, and 15m/s in amplitude, and 26 different directions were generated as disturbance for each simulation run. Whereas the munition with the spin speed of 3 rps didn’t flip, that with 1-rps spin flipped under some gusts. However, the gusts which increase airspeed in the flight direction didn’t introduce harmful effect. Most importantly, all the flips of the munition was observed near the end of the simulation where the munition is going down. No problem was observed near the summit of trajectory.

충격파 형상을 고려한 2단 경사면 초음속 공기 흡입구 설계

남승화(SeungHwa Nam),장경민(KyungMin Jang),서송원(SongWon Seo),정필규(PilGyu Jeong),정은상(EunSang Jung),권세진(SeJin Kwon) 한국항공우주학회 2020 한국항공우주학회 학술발표회 논문집 Vol.2020 No.11

고체연료 램제트 개념 설계 연구

남승화(SeungHwa Nam),장경민(KyungMin Jang),서송원(SongWon Seo),정필규(PilGyu Jeong),정은상(EunSang Jung),권세진(Sejin Kwon) 한국추진공학회 2020 한국추진공학회 학술대회논문집 Vol.2020 No.11

본 연구에서는 전산유체역학을 이용하여 155 mm 고체연료 램제트 포탄을 설계하였다. 필요한 기본 매개변수들을 설정하였으며 이를 이용하여 초기 수치를 결정하였다. 전산수치해석을 이용하여 성능을 고려한 경사면 각도를 정하였고 충격파 위치가 Cowl lip에 중첩되게 하는 2단 경사면을 가지는 흡입구를 설계하였다. 연료 그레인은 HTPB에 AP파우더 15 wt.%, Al 파우더 5 wt.%가 혼합된 형태로 구성되어 있다. 연료 그레인의 연소 반응식을 이용해 연소실 전산수치해석을 진행하였으며 요구추력이 발생함을 확인하였다. In this study, a 155 mm solid fuel ramjet projectile was designed using computational fluid dynamics. Set the necessary parameters required for the design, and the initial values were determined using them. The inclination angle considering the performance was determined and designed the supersonic inlet with a two-stage slope that superimposed the shock wave on the cowl lip using computational fluid dynamics. The fuel grain consists of a mixture of HTPB with 15 wt.% AP powder and 5 wt.% Al powder. Computational fluid dynamics of the combustion chamber was carried out using the species reaction of the fuel grain, and it was confirmed that the required thrust was created.

포신의 강선을 고려한 포 발사 해석

주근수(Geunsu Joo),허훈(Hoon Huh),정영혁(Yeong Hyuk Jung),김주영(Ju Yeong Kim),서송원(Songwon Seo) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.9

본 논문에서는 포신의 강선을 고려한 포 발사 해석기법을 다룬다. 포 발사 환경에서 탄두는 고충격 및 고회전의 동적 거동이 발생한다. 이러한 동적 거동에서 탄두 및 탄두 내 전자 장비가 손상되는 사례가 발생하고 있다. 따라서 포 발사 환경에서 탄두의 동적 거동 분석 및 생존성 평가를 위한 포 발사 해석기법의 개발이 필요한 실정이다. 본 논문에서는 앞서 선행연구자들의 단순화된 포 발사 해석기법을 개선하여, 포신의 강선과 탄대의 접촉에 따른 탄두의 회전을 구현할 수 있는 포 발사 해석기법을 개발하였다. 개발된 포 발사 해석기법은 실험결과와 비교를 통하여 검증하였으며, 제안된 해석기법을 이용하여 포 발사 시 탄두의 동적 거동 및 생존성을 평가하였다. This paper is concerned with numerical simulation of a gun-launched projectile considering a rifled gun-tube. Gun-launched conditions induce dynamic behaviors, such as high pressure and high speed rotation. A projectile and its internal electronic components may be damaged in such harsh environments. Hence, it is necessary to perform numerical simulation of a gun-launched projectile to predict its dynamic behaviors and stability. In this work, preceding research studies on gun-launched projectiles are investigated, and the simulation method is developed to rotate the projectile through between its rotating band and a rifled-gun tube. The proposed method is verified by comparison with experimental results, and the dynamic behaviors and stability of the projectile are evaluated under gun-launched conditions.

비행 시험을 통한 저속 회전 유도형 탄약의 롤각 추정 성능 검증

박준우(Junwoo Park),정우영(Wooyoung Jung),방효충(Hyochoong Bang),김진원(Jin-Won Kim),허준회(Junhoe Heo),박장호(Chang-Ho Pak),서송원(Songwon Seo) 한국항공우주학회 2020 韓國航空宇宙學會誌 Vol.48 No.9

본 논문에서는 유도형 탄약의 모사 기체를 제작하고 공중에서 탄체에 롤축 회전을 인가한 뒤 롤축 저속 회전 중인 탄체의 롤각 추정 성능을 실험적으로 검증한 방법과 결과를 소개한다. 멀티로터형 무인기를 모선으로 사용해 유도형 탄약 모사 기체에 초기 속도와 고도를 부여하였으며 탄체투하, 탄체 회전, 롤각 추정 및 안정화로 이어지는 비행 시험 시나리오를 통해 롤각 추정 결과를 분석한다. 약 200m의 고도에서 수평 방향으로 15㎧의 속력으로 탄체를 투하한 뒤 내부의 반동차(Reaction Wheel)를 사용하여 탄체를 회전시켰으며 특히, 상용 GPS/INS와의 비교를 통해 롤각 추정 결과를 제시한다. 아울러, 반동차를 이용하여 공중에서 탄체를 롤축 회전시키는 메커니즘들을 비교하고 실제 구현한 결과도 소개한다. This paper presents methods and results of both flight test examining roll angle estimation performance of slowly rolling munition forced to spin in the air, and fabricating a replica of guided munition. Guided munition was deployed from multi rotor type UAV mother ship whose altitude and velocity was conveyed to it as initial state. Flight test scenario is composed of a sequence of munition drop(deployment), munition spin, roll angle estimation and stabilization. Munition was deployed from mother ship at around 200m high with horizontal velocity of 15㎧, and was made spun using internal reaction wheel. Performance analysis on roll angle estimation is provided in comparison with commercial aerospace graded GPS/INS. Moreover, several mechanisms that rotates munition using reaction wheel, and actual product that realizes one of them are introduced.