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문상돈,김연직,임익태,박찬우 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
As a technology to machine the 3-dimensional shapes of general metal material more flexibly, machining technologies such as metal cutting, grinding, etc have been steadily improved in their accuracy as well. However, the working method using machining technologies are restricted in terms of surface roughness, metal working accuracy and working hours, if a workpiece has an irregular 3-dimensional shape. Magnetic abrasive finishing process is also one of the super-precision machining technologies which proceed with the finishing metal working of precision working piece using the action of magnetic field and the mixed type magnetic abrasive. However, such studies only focus on the improvement of machining accuracy but are still incomplete in investigating the roundness. This study aims to realize the high accuracy finishing machining focusing on the roundness after magnetic abrasive finishing process of circular workpiece and the surface roughness of precision machining surface.
VARTM 법으로 제작한 탄소-유리/에폭시 하이브리드 적층재의 인장 특성
김연직 ( Yon Jig Kim ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.10
This paper presents a study of the tensile behavior of carbon and glass fiber reinforced epoxy hybrid laminates manufactured by vacuum assisted resin transfer molding (VARTM). The objective of this study was to develop and characterize carbon fiber reinforced plastic hybrid composite material that is low cost and light-weight and that possesses adequate strength and stiffness. The effect of position and content of the glass fabric layer on the tensile properties of the hybrid laminates was examined. The strength and stiffness of the hybrid laminates showed a steady decrease with an increase of the glass fabric content this decrease was almost linear. Fracture strain of these laminates showed a slight increasing trend when glass fabric content was increased up to 3 layers, but at a glass fabric content > 3 layers the strain was almost constant. When glass fabric layers were at both outer surfaces, the hybrid laminate exhibited a slightly higher tensile strength and elastic modulus due to the small amount of glass yarn pull-out.
A Study on Fatigue Crack Propagation Mechanism of GFRP in Synthetic Sea Water
Kim, Yon-Jig,Lim, Jae-Kyoo The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.10
This paper evaluates the fatigue fracture behavior of a chopped strand glass mat/polyester composite both in ai, and sea water, Bending fatigue (R=-1) was performed on dry and wet specimens, that is respectively in air and sea water. Where the pH concentration of sea water was controlled to 6.0,8.2, 10.0 and the wet specimens were immersed in the sea waters for 4 months. Throughout the tests, fatigue cracks both in the dry and wet specimens, tested in the air or sea water, occurred at the beginning of the cycle, followed by either of two regions one decreasing and the other increasing as the crack growth rate increases.
Mechanical properties of biodegradable coconut fibre reinforced polylactic acid composite
Kim Yon Jig(김연직),Phan Quoc Thai(판꾹타이),Renliang Wang(왕렌리앙),Jun Yong Choi(최준용),Ruihua Hu(후루이화),Jae Kyoo Lim(임재규) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
In the recent years, the use of natural fiber as reinforcements in polymer composites for replacing synthetic fiber is rapidly increased. Coconut is growing in some tropical countries such as Vietnam, Thailand, India... especially, it is very cheap and infinite resource. Polylactic acid (PLA) is a biodegradable thermoplastic polymer, which was used extensively in recent years because the biodegradable composites are friendly with environment. This study is concerned with the mechanical properties of coconut fiber (coir) reinforced PLA composite. The coconut fiber reinforced PLA composite was manufactured by heating compression mold with different contents of coconut fiber. The tensile test and bending test will be carried out to verify the mechanical properties of composite and the effect of coconut contents to them.
권일현,김연직,정세희 전북대학교 공업기술연구소 1991 工學硏究 Vol.22 No.-
Recently, the FRP are widely used in many industrial areas which are required to the light-weight and the high strength. But water absorption proved to be lessen about the mechanical properties of these materials. Therefore, the objection of this study was observed that we maked laminates as used that matrix is unsaturated liqued polyester material absorbed the distilled water of constant quantity and no water absorption materials are used to obsorbed the distilled water of constant quantity and no water absorption materials are used to observe the change of fatigue strength, fatigue crack propagation behavior, tensile properties. The results obtained through these tests are as follow ; (1) In case of the glass fiber reinforced polyester composite materials, the fatigue crack in the both no water absorption material and a water absorption material occurred at the initial of cycle. Thereafter, it was divided with two regions that one was decreased a crack extenstion and the other was increased a crack extenstion. (2) The stable fatigue crack growth period(region Ⅱ)was shorted by distilled water absorption and resulted in shortening of fatigue life.