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정동택(Dong Teak Chung),박치영(Chi Young Park),진두한(Doo Han Jin),김태연(Tae Yeon Kim),이주연(Joo Yeon Lee),이인석(Ihnseok Rhee) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.9
방탄소재로서 사파이어 재료가 대두되고 있지만 고속 충돌관련 동적거동 및 파괴특성에 관한 연구는 부족한 실정이다. 탄자와 취성세라믹재료간의 상호작용을 연구하기 위해서는 고화질의 초고속 연속영상이 필수적이다. 본 연구에서는 고속충돌 및 관통 현상을 순차적으로 촬영할 수 있는 장치를 개발하였다. 이 장치는 속도측정장치, 마이크로프로세서를 사용한 카메라 구동장치 그리고 다수의 CCD카메라로 이루어져있다. 선형배열센서를 사용한 속도측정장치는 직경 1-2 mm 탄자의 마하 3 속도를 측정할 수 있다. 발사된 탄자가 속도측정장치를 통과하면 속도와 시간이 측정되고 탄자가 비행하는 동안 카메라 구동장치가 정확한 충돌시간을 계산하여 다수의 카메라에 순차적으로 트리거 신호를 보내서 충돌전후의 형상을 순차적으로 촬영한다. 정확한 충돌시간 예측을 못하면 고해상도의 사진촬영이 거의 불가능하다. 본 연구에서 개발된 정밀 촬영장치를 사용하여 고해상도의 영상을 확보할 수 있었다. A single-crystal sapphire is used as a transparent bulletproof window material; however, few studies have investigated the dynamic behavior and fracture properties under high-speed impact. High-speed and high-resolution sequential images are required to study the interaction of the bullet with the brittle ceramic materials. In this study, a device is developed to capture the sequence of high-speed impact/penetration phenomena. This system consists of a speed measurement device, a microprocessor-based camera controller, and multiple CCD cameras. By using a linear array sensor, the speed-measuring device can measure a small (diameter: up to 1- 2 mm) and fast (speed: up to Mach 3) bullet. Once a bullet is launched, it passes through the speed measurement device where its time and speed is recorded, and then, the camera controller computes the exact time of arrival to the target during flight. Then, it sends the trigger signal to the cameras and flashes with a specific delay to capture the impact images sequentially. It is almost impossible to capture high-speed images without the estimation of the time of arrival. We were able to capture high-speed images using the new system with precise accuracy.
정동택(Dong Teak Chung),박치영(Chi Young Park),진두한(Doo Han Jin),김태연(Tae Yeon Kim),이주연(Joo Yeon Lee),이인석(Ihnseok Rhee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Single crystal sapphire is used for transparent bulletproof window material, but the research of dynamic behavior and fracture properties under high-speed impact has rarely been done. High speed and high resolution sequential images are required to study the interaction of the bullet with the brittle ceramic materials. This paper is about a device developed to capture the sequence of high-speed impact/penetration phenomena. This system consists of a speed measurement device, a microprocessor based camera controller, and multiple CCD cameras. By using linear array sensor, the speed-measuring device can measure a small(up to 1-2㎜ in diameter) and fast(up to Mach 3) bullet. Once a bullet is launched then it passes through the speed measurement device to register the time and the speed then the camera controller computes the exact time of arrival to the target during the flight. Then, it sends the trigger signal to the cameras and flashes with specific delay to capture the impact images sequentially. It is almost impossible to capture high speed image without estimation of the time of arrival. We were able to capture the high speed images using the new system with precise accuracy.
정동택(Dong-Teak Chung),진두한(Doo-han Jin),강형(Hyung Kang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The nose of a missile, flying through raining region with a supersonic speed, is subjected to the rain erosion because the nose is made of a brittle ceramic material. A simple yet very effective rain erosion test method is developed. The sabot assembly similar to the hypodermic syringe carries specific amount of water is launched by a low pressure air gun. After the stopper stop the sabot assembly by impact, the steel plunger continues moving toward to squeeze the silicon rubber in front. The pressurized silicon rubber then is squeezed through the orifice in front of the sabot at high velocity, thus, accelerates the water droplet to higher velocity. The droplet velocity up to 800㎧ is successfully attained using a low pressure air gun. The ceramic specimen assembly is placed in front of the high speed water droplet and the rain erosion damage on the surface of the specimen is observed.
소형구의 속도증폭을 위한 사보 조립체의 실리콘고무 특성 연구
김영민,진두한,정동택,Kim, Young-Min,Jin, Doo-Han,Chung, Dong-Teak 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.4
A mini ball launch system was developed for the study of dynamic fracture of ceramic materials. The principle of velocity multiplication system is similar to two stage gun. The plastic sabot assembly houses steel plunger and the void filled with silicone rubber. The sabot is stopped by the stopper block then the steel plunger inside the sabot compress the silicone rubber to high pressure. Then the compressive energy of the silicone rubber is transferred to the ball. More than ten times of initial speed was attained. In this study, most effective silicone rubber for the highest final speed was chosen out of three different varieties by launch tests.
다공성 소재를 사용한 운반용 공기 부상시스템 개발에 관한 연구
이상걸(Sang-Geol Lee),정동택(Dong-Teak Chung),정경석(Kyung-Seok Jeong),김태연(Tae-Yeon Kim) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
When using a conveyor for the movement of a surface-treated object, there is a high possibility that the surface of the object is damaged by friction with the surface of the conveyor. In order to prevent such surface damage, it is an alternative to use a method of making the object slip by using the pneumatic pressure. In order to float an object from the surface, a large number of air holes must be made on the surface so that the pneumatic pressure is evenly dispersed, and this processing causes an increase in the production cost. In this study, we have carried out a study to apply the air floating system which moves by floating the object using the low cost porous material as a substitute method, and it confirms the validity of the method of transporting without damaging the surface of the object.
진두한(Doo Han Jin),정동택(Dong Teak Chung),박치영(Chi Young Park),이인석(Ihnseok Rhee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
A mini ball acceleration system was developed for the study of dynamic fracture of ceramic and single crystal materials. This system consists of (1) low pressure gas gun, (2) sabot assembly, (3) stopper block with plastic membrane for second acceleration, (4) velocity measurement device for sabot and ball, and (5) enclosed target box. The plastic sabot assembly houses steel plunger and the void filled with silicone rubber. The sabot is stopped by the stopper block then the steel plunger inside the sabot compress the silicone rubber to high pressure to rupture the plastic membrane. Then the compressive energy of the silicone rubber is transferred to the ball. More than ten times of initial speed was attained. Non-contact velocity measurement system is measuring the supersonic speed of the mini ball. Maximum speed up to 1200m/s for plastic and 700m/s for steel ball was attained. Perforation test of glass window was successfully done by the developed impact system.
박명수(Myungsoo Park),유정훈(Jeonghoon Yoo),정동택(Dong-Teak Chung) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.10
To predict the behavior of dual plate, 5052 aluminum and 1002 cold rolled steel, numerical and experimental approaches are attempted. For a numerical analysis, explicit finite element code, NET2D is utilized to consider nonlinear characteristics of materials under the ballistic impact. To characterize mechanical features of each plate, material properties of the Johnson-Cook constitutive model are generated by fitting the parameters from tensile test and impact test. Based on the numerical results, multi-objective optimization to minimize mass and maximize strength of dual plate is achieved. In addition, the air-gap effect is researched.