• 항공우주기술
• /
• 제13권2호
• /
• pp.177-184
• /
• 2014

우주발사체의 비행안전분석은 정상 및 비정상 비행으로 인해 발생되는 파편의 낙하점 및 낙하분산영역을 예측하여 인명, 선박 그리고 항공기에 미치는 영향을 분석하게 된다. 낙하점 및 낙하분산영역 예측은 우주발사체의 비행안전분석에 필수 요소이다. 특히, 낙하분산영역은 몬테카를로 시뮬레이션을 적용하여 예측될 수 있다. 이럴 경우, 수백회 이상의 반복 계산이 요구되는 몬테카를로 방법은 낙하분산영역을 산출하는데 많은 시간이 소요된다. 본 논문에서는 몬테카를로 시뮬레이션을 대체할 수 있는 방안으로 JU 변환과 다구치 방법을 적용해보고, 세가지 방안의 결과를 비교하여 낙하분산영역 계산을 위해 적합한 방법을 제시한다.

• 한국항공우주학회지
• /
• 제32권7호
• /
• pp.51-59
• /
• 2004

저속충격에 의한 복합재의 파손 모드를 규명하기 위하여 PVDF 센서를 이용한 신호취득 방법과 측정된 PVDF 센서 신호를 시간-주파수 분석법 (time-frequency analysis)인 국소 퓨 리에 변환 및 웨이블렛 변환을 적용하여 분석할 수 있는 실험적 전차에 대하여 고찰하였다. 고분자 암전센서를 이용하여 저속충격시 발생할 수 있는 여러 충격손상 형태 모재균열, 층간분리, 섬유파단에 의한 응력파 측정 가능성을 고찰하기 위하여 일련의 저속충격 시험을 수행하였다. 충격 시험 후, 저속 충격을 받은 적층판에 대하여 C-scan 과 단면 검사를 통하여 센서 신호, 손상 모드 및 크기에 대한 상관관계를 고찰하였다. 센서신호의 취득과 신호분석을 통하여 저속충격의 발생/진행과정을 알 수 있는 많은 중요한 정보가 PVDF 센서신호에도 내재되어 있음을 알 수 있으며 PVDF 센서 신호를 주의 깊게 분석함으로써 저속 충격에 의한 복합재료의 손상 모드 규명이 가능하며 저속충격 위협에 대한 복합재 구조물의 건전성 모니터링에 활용할 수 있는 가능성을 제시하였다.

• 한국운동역학회지
• /
• 제20권1호
• /
• pp.25-32
• /
• 2010

This study was performed to investigate the kinematic factors on the head hitting motion based on weight change of bamboo swords in kumdo. The kinematic factors, needed time per phase, COB displacement and velocity, angle(wrist, elbow, shoulder joint, hip joint, knee joint), were analyzed by the 3-D motion analysis method against 6 male middle school athletes. The results were as follows. 1. The needed time of head hitting motion based on weight change of bamboo swords was shorter when weight was heavier. 2. The COB displacement of left/right was bigger when weight was heavier. the displacement of right foot was higher at backswing phase and impact phase when weight was heavier and at impact time when weight was lighter. 3. The COB velocity was faster at impact time when weight was heavier, the velocity of sword tip was fastest for each event with bamboo sword weight of 440 g. 4. The angle of left elbow was smaller at top of backswing and impact when weight was heavier, the angle of left shoulder was bigger when weight was heavier, the right knee angle was biger at start when weight was heavier, at impact when weight was lighter.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.459-464
• /
• 2004

The rifle impact of human body affected by the posture of human for rifling. The interaction human-rifle system influence the firing accuracy. In this paper, impact analysis of human model for shooting posture is carried out. ADAMS code and LifeMOD is used in impact analysis of human model and modeling of the human body, respectively. On the shooting, human model is affected by rifle impact during the 0.001 second. Performed simulation time for shooting is 0.1 second. Applied constraint condition to human-rifle system is rotating and spherical condition. As the results, the displacement of rifle and transfer path analysis of impact of human model is presented.

• Structural Engineering and Mechanics
• /
• 제60권5호
• /
• pp.829-849
• /
• 2016

In this paper, experimental as well as numerical analysis of Glass Fiber Reinforced Polymer (GFRP) laminated composite has been presented under ballistic impact with varying projectile nose shapes (conical, ogival and spherical) and incidence velocities. The experimental impact tests on GFRP composite plate reinforced with woven glass fiber ($0^{\circ}/90^{\circ}$)s are performed by using pneumatic gun. A three dimensional finite element model is developed in AUTODYN hydro code to validate the experimental results and to study the ballistic perforation characteristic of the target with different parametric variations. The influence of projectile nose shapes, plate thickness and incidence velocity on the variation of residual velocity, ballistic limit, contact force-time histories, energy absorption, damage pattern and damage area in the composite target have been studied. The material characterization of GFRP composite is carried out as required for the progressive damage analysis of composite. The numerical results from the present FE model in terms of residual velocity, absorbed energy, damage pattern and damage area are having close agreement with the results from the experimental impact tests.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1995년도 추계학술대회 논문집
• /
• pp.773-777
• /
• 1995

This thesis attempt to explore the shape of stress wave propagation of 3-dimensional stress field which is made in the process of time increment. A finite element code about 3-dimensional stress wave propagation is developed for investigating the changing shape of the fracture by the impact load. The Finite Element Code, which is the solution for the 3-dimensional stress wave analysis, based on Galerkins and Newmark- .betha. method at time increment step. The tensile stress and compressive stress become larger with the order of the middle, the upper and the opposite layers when the impact load is applied. In a while the shear stress become larger according to the order of the upper, the middle and the opposite layers when impact load applied.

• 한국전산구조공학회논문집
• /
• 제24권6호
• /
• pp.715-722
• /
• 2011

본 논문에서는 항공기 충돌에 의한 원전 격납건물의 거동을 병렬해석을 통해 수행하였다. 지금까지의 원전 격납건물에 대한 항공기 충돌관련 연구는 항공기의 경우, Riera의 충격하중-시간함수를 이상화하여 대상 구조체의 일정영역에 대해 충격하중으로 적용하는 방법을 사용해 왔고 충돌대상 구조체의 경우, 단순 철근콘크리트 벽체나 빌딩에 머물러 왔다. 하지만 본 논문에서는 항공기(Boeing-767, http://www.boeing.com)와 가상의 원전 격납건물을 실제와 유사하게 모델링하여 해석을 수행하였으며, 항공기모델은 충돌평가 가이드인 NEI 07-13(2009)에서 허용하는 Riera의 식에 따른 충돌하중이력곡선과 비교하는 방법으로 검증되었다. 또한, 일반적으로 고속 충돌해석은 짧은 시간동안 두 개 이상의 물체가 접촉하고 동적 대변형을 일으키는 비선형성이 강한 문제로 많은 계산시간이 요구되기 때문에 이를 효과적으로 다루기 위해서는 단일 CPU만으로는 한계가 있다. 따라서 본 논문에서는 해석의 효율성을 향상시키기 위해 자체 구축한 리눅스 클러스터 시스템을 이용하여 Message-Passing MIMD 형태의 병렬해석을 수행하였고 병렬성능에 대한 평가를 위해 무근콘크리트(Plain Concrete, PC), 철근콘크리트(Reinforced Concrete, RC), 내부 Liner Plate를 부착한 철근콘크리트(RC with Containment Liner Plate, CLP), SC구조(Steel-Plate Concrete, SC)등 4가지 경우에 대한 수치해석 효율성이 비교 검토되었다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
• /
• pp.407-412
• /
• 1998

In this work, a new time integration method is proposed using the generalized derivative concept to simulate the dynamic phenomena having sudden constraint occurring in dynamic contact/impact problems. By the adoption of the generalized derivative concept and jump assumption, discontinuity can be incorporated in time integration and as a result, the algorithm does not need any other special consideration of jumps in dynamic field variables due to sudden constraint like dynamic contact-release conditions. To observe the characteristics of the proposed time integration method, the stability and convergence analyses are carried out. In numerical tests, several dynamic contact/impact problems are analyzed by straightforward application of the proposed time integration method with the exterior penalty method.

• 한국운동역학회지
• /
• 제30권2호
• /
• pp.145-154
• /
• 2020

Objective: The purpose of this study was to determine the relationship between impact and shear peak force, and tibia-accelerometer variables during running. Method: Twenty-five male heel strike runners (mean age: 23.5±3.6 yrs, mean height: 176.3±3.3 m/s, mean mass: 71.8±9.7 kg) were recruited in this study. The peak impact and anteroposterior shear forces during treadmill running (Bertec, USA) were collected, and impact shock variables were computed by using a triaxial accelerometer (Noraxon, USA). One-way ANOVA was used to test the influence of the running speed on the parameters. Pearson's partial correlation was used to investigate the relationship between the peak impact and shear force, and accelerometer variables. Results: The running speed affected the peak impact and posterior shear force, time, slope, and peak vertical and resultant tibial acceleration, slope at heel contact. Significant correlations were noticed between the peak impact force and peak vertical and resultant tibia acceleration, and between peak impact average slope and peak vertical and resultant tibia acceleration average slope, and between posterior peak (FyP) and peak vertical tibia acceleration, and between posterior peak instantaneous slop and peak vertical tibial acceleration during running at 3 m/s. However, it was observed that correlations between peak impact average slope and peak vertical tibia acceleration average slope, between posterior peak time and peak vertical and resultant tibia acceleration time, between posterior peak instantaneous slope and peak vertical tibial acceleration instantaneous slope during running at 4 m/s. Conclusion: Careful analysis is required when investigating the linear relationship between the impact and shear force, and tibia accelerometer components during relatively fast running speed.

• 한국터널지하공간학회 논문집
• /
• 제12권3호
• /
• pp.247-255
• /
• 2010

숏크리트의 부착강도는 천정부의 낙반방지와 발파진동에 의한 숏크리트 탈락방지에 중요한 역할을 하는 요소이다. 따라서, 숏크리트의 부착상태평가는 품질관리의 주요 요소가 될 수 있다. 본 연구는 터널 내 발파에 의하여 숏크리트에 미치는 최대 입자속도를 예측하고, 발파 진동에 의한 숏크리트의 부착상태를 평가하기 위하여 수행되었다. 이를 위하여 현재 시공중인 터널현장에서 피난연락갱의 발파시 본선부 및 서비스 터널의 발파진동을 측정하였으며 충격반향시험을 수행하여 숏크리트-암반의 부착상태를 평가하였다. 충격반향시험 신호분석을 위하여 시간-주파수 영역 해석 기법을 도입하였으며 평가결과, 국내에서 일반적으로 시행되는 발파조건에서는 숏크리트와 암반의 부착력 손실(들뜸 현상)은 거의 발견되지 않았으며, 숏크리트 부착력 손상 가능성은 낮은 것으로 판단되었다.