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플라스틱 소재의 고 변형률 인장특성 평가를 위한 홉킨스바(Split Hopkinson Pressure Bar) 측정 장비에 관한 연구
한인수,이세민,김규원,김학성,Han, In-Soo,Lee, Se-Min,Kim, Kyu-Won,Kim, Hak-Sung 한국복합재료학회 2022 Composites research Vol.35 No.3
Split Hopkinson Pressure Bar (SHPB) is a general test equipment for measuring the mechanical properties of high modulus metal and composite materials at high strain rate. However, for the soft plastic material, it is difficult to hold the specimen and achieve dynamic stress equilibrium due to the weak transmitted signals. In this study, SHPB test apparatus were designed to measure accurately the high strain rate stress-strain curve of the soft plastic materials by changing the incident bar materials and the shape of the specimen holder parts. In addition, to verify the high strain-rate tensile strain data obtained from SHPB, the strain distribution of the specimen was measured and analyzed with a high-speed camera and the digital image correlation (DIC), which was compared with the strain history measured from SHPB.
Ir-192 방사선원의 밀봉 용접부 품질에 미치는 저항용접 공정변수의 영향
한인수,손광재,이영호,이유황,이준식,장경덕,박울재,박춘득,Han, In-Su,Son, Kwang-Jae,Lee, Young-Ho,Lee, You-Hwang,Lee, Jun-Sig,Jang, Kyung-Duk,Park, Ul-Jae,Park, Chun-Deuk 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.1
Ir-192 radiation sealed sources are widely employed to the therapeutic applications as well as the non-destructive testing. Production of Ir-192 sources requires a delicate but robust welding technique because it is employed in a high radioactive working environment. A GTA(Gas Tungsten Arc) welding technique is currently well established for this purpose. However, this welding method requires a frequent replacement of the electrode, which results in the delay of the production to take a preparatory action such as to isolate the radiation sources from the working place before getting access to the welding machine. Hence, a resistance welding technique is considered as an alternative method of the GTA welding technique. The advantages of resistance welding are high welding speed and high-rate production. Also it has very long life of electrode comparing to GTA welding. In this study, the resistance welding system and proper welding conditions were established for sealing Ir-192 source capsule. As a results of various experiments, it showed that electrode displacement can be employed as a indicator to predict welding quality. We proposed two mathematical models(linear and curvilinear) to estimate electrode displacement with process parameters such as applied force, welding current and welding time by using regression analysis method. Predicting results of both linear and curvilinear model were relatively good agreement with experiment.