• 한국표면공학회지
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• 제41권6호
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• pp.301-307
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• 2008

In this paper, nanocrystallization of CuNiTiZr bulk metallic glass (BMG) subjecting to a kinetic spraying, dependent on impact velocity, was investigated by numerical and experimental approaches. The crystallization fraction and nucleation activation energy of initial feedstock and as-deposited coating were estimated by DSC and Kissinger method, respectively. The results of numerical modeling and experiment showed that the crystalline fraction and nucleation activation energy in BMG coatings were depended on kinetic energy of incident particle. Upon impact, the conversion of particle kinetic energy leads to not only decreasing free energy barrier but also increasing the driving force for an amorphous to crystalline phase transformation. The nanocrystallization of BMGs is associated with the strain energy delivered by a plastic deformation with a high strain rate.

• 대한안전경영과학회지
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• 제10권2호
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• pp.85-94
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• 2008

The object of this study is to investigate the penetration characteristics according to the change of stacking sequences and curvature radius in the composite laminated shell. They are staked to [02/902]S and [0/902/0]s, their interlaminar number are two and four. We are manufactured to composite laminated shells with various curvature radius. Curvature radius of composite shell is 100, 150, 200mm and ${\infty}$(it's meaning flat-plate). In general, kinetic energy after impact-kinetic energy before impact increased linearly in all specimens. Absorbed energy increased linearly as the curvature increased, and absorbed energy of [02/902]S specimen, which is small interlaminar number, was higher than [0/902/0]s specimen.

• 한국운동역학회지
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• 제13권2호
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• pp.175-183
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• 2003

The purpose of this study was to analyze the kinetic energy of putter head and ball movements during the process of impact. Highly skilled 5 golfers(less than 1 handicap) participated in this study and the target distance was 3 m. Movements of ball and putter head were recorded with 2 VHS video cameras(60 Hz, 1/500 s shutter speed). Small control object($18.5{\times}18.5{\times}78.5\;cm$) was used in this sdtuldy. Analyzing the process of impact, putter was digitized before 0.0835 s and after 0.0835 s of impact. Ball was digitized 0.1336 s after impact. The results showed that the maximum speed was appeared at Impact and prolonged for a while. Contact point of the club head was within 0.7 cm to the z axis. After contacting the club head, the ball was moved above the ground level(slide) and returned to the ground with sliding and rolling. After contacting the ground, the speed of ball was relied on the surface of the ground. During impact, 70% of kinetic energy of club head has been transferred to the ball.

• Composites Research
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• 제26권3호
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• pp.175-181
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• 2013

고속충격을 받는 복합재 적층판의 충격거동 특성 중에서 관통 후 잔류속도, 시편에 의한 충격흡수에너지 그리고 충격손상영역에 대한 평가와 예측이 중요하다. 본 논문에서는 고속충격을 받는 Carbon/Epoxy 복합재 적층판의 잔류속도와 흡수에너지를 준실험적 방법을 통하여 예측할 수 있는 방법을 제안하였다. 고속충격에 의한 시편의 흡수에너지를 정적에너지와 동적에너지로 구분하였으며 정적에너지는 보강섬유의 파손과 정적 탄성에너지와 관련 있는 준정적압입실험을 통한 관통에너지를 사용하였다. 동적에너지는 고속충격 시 시편 일부의 움직임과 관련한 운동에너지에 대하여 몇 가지 모델을 제안하여 비교하였다. 공압을 이용한 고속충격실험을 수행하고 예측 값과 비교 분석하였다. 시편의 손상영역은 C-scan을 통하여 측정하였다. 관통한계속도보다 큰 초기 속도인 경우, 정적에너지인 관통에너지 뿐 만 아니라 시편의 동적 에너지가 시편 전체 흡수에너지에 크게 기여함을 알 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.416-419
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• 2004

The kinetic energy during ship collision with bridge piers is released as the permanent deformations of structure and friction between the impact surfaces. So the ship collision energy is estimated from the equations of motions for ship-pier collisions which include the influence of the surrounding water, different impact angles and impact locations. The normal impact energy and tangent impact energy at a collision location and angle can be transformed into the normal impact force and friction force acting on the structure. Also the kinetic energy after collisions is calculated from the linear and angular impulse of ship collisions. The collision energy absorption system such as the protective structures for bridges is designed by evaluating the damage portions of ship and structure during the ship-structure collisions varying from the soft impact to hard impact and then the estimation of it will be suited for the design of protective measures.

• Structural Engineering and Mechanics
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• 제71권2호
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• pp.109-118
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• 2019

This paper presents the numerical simulation of membrane structure under impact load. Firstly, the numerical simulation model is validated by comparing with the test in Hao's research. Then, the effects of the shape of the projectile, the membrane prestress and the initial impact speed, are investigated for studying the dynamic response and failure mechanism, based on the membrane displacement, projectile acceleration and kinetic energy. Finally, the results show that the initial speed and the punch shape are related with the loss of kinetic energy of projectiles. Meanwhile, the membrane prestress is an important factor that affects the energy dissipation capacity and the impact resistance of membrane structures.

• 한국전자통신학회논문지
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• 제14권4호
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• pp.743-754
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• 2019

지표면 침식 잠재력은 비가 내린 영향으로 토양에 전달 된 운동 에너지로 평가할 수 있다. 충격 신호를 분석할 수 있는 디즈드로미터로 우적 에너지율 관계식을 산출하였다. 대륙 강수의 97%와 해양 강수의 95%가 강우량과 강우율의 관계로 이루어진 이 지수 방정식으로 설명되었다. 이 관계식의 지수는 강우 유형에 의존하지 않지만 계수는 강우 사건에 따라 조정될 수 있는 변동을 나타냈다. 이 관계식은 결정 계수, 평균 절대 오차 및 신뢰 오차에 의해 검증되었다. 특정 유형의 토양과 관련된 강수의 운동 에너지는 강우로 인한 침식의 가능성을 결정할 수 있다.

• Journal of Welding and Joining
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• 제26권6호
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• pp.74-80
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• 2008

A finite element modeling approach has been described for the simulation and analysis of the micron-scaled solid particle impact behavior in kinetic spraying process, using an explicit code (ABAQUS 6.7-2). High-strain-rate plastic deformation and interface bonding features of the copper, nickel, aluminum, and titanium were investigated via FEM in conjunction with the Johnson-Cook plasticity model. Different aspects of adiabatic shear instabilities of the materials were characterized as a concept of thermal boost-up zone (TBZ), and also discussed based upon energy balance concept with respect to relative recovery energy (RRE) for the purpose of optimizing the bonding process.

• 한국실천공학교육학회논문지
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• 제2권1호
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• pp.154-163
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• 2010

본 연구에서는 터보차저 및 인터쿨러, 블루 오프 밸브 등 튜닝 부품을 장착한 스쿠푸 알파 차량의 경우 N/A엔진에 비해 흡입 공기량의 변화가 오게 되고 이에 따른 연료 보정 및 ECU의 튜닝을 목적으로 연구되었다. 이와 같은 터보 엔진은 압축압력의 변화가 있게 되며 이때 인위적으로 개스킷의 두께를 조절하여 압축비에 변화를 주게 되면 엔진의 출력 특성 변화를 살펴볼 수 있다. 시험은 제동압력이나 마력 측정이 불가능하므로 ECU튜닝 장비인 모텍 라서치(주)의 Engine Management System장비를 기본으로 시험하였고 성능 공식 전개를 통하여 출력의 변화를 살펴보았다. 엔진 다이나모미터 시험보다 엔진 ECU데이터를 사용하기 때문에 개발된 ECU 데이터를 이용하면 튜닝엔진에 바로 접목시킬 수 있어 앞으로 튜닝 정비 분야에서 많이 필요로 할 것으로 예측된다. 또한 본 연구를 통하여 학생들은 전자제어엔진에 대해 섬도 있는 학습이 되었으며, 정비 관련 산업체에서도 ECU데이터를 이용하여 엔진의 성능을 점검하고 체계적으로 제어할 수 있는 기술의 방향과 토대를 마련하였다고 본다.

• Journal of Welding and Joining
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• 제25권3호
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• pp.37-44
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• 2007

Mechanical and thermomechanical properties of the bulk metallic glass (BMG) are so unique that the deformation behavior is largely dependent on the temperature and the strain rate. Impacting behavior of NiTiZrSiSn bulk metallic glass powder during kinetic spraying was investigated in this study. Considering the impact behavior of the BMG, the kinetic spraying system was modified and attached the powder preheating system to make the transition from the inhomogeneous deformation to the homogeneous deformation of impacting BMG particle easy BMG splat formation is considered from the viewpoint of the adiabatic shear instability. It is suggested that the impact behavior of bulk metallic glass particle is determined by the competition between fracture and deformation. The bonding of the impacting NiTiZrSiSn bulk amorphous particle was primarily caused by the temperature-dependent deformation and fracture (local liquid formation) behavior.