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압출적층조형 공정 기반 3D 프린팅 제품 기계적 특성의 지배적 공정인자 도출 및 최적화에 관한 연구
김정섭(Jung Sub Kim),조난현(Nanhyeon Jo),남정수(Jung Soo Nam),이상원(Sang Won Lee) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.7
최근 다양한 분야에 적용되고 있는 적층 가공 기술(AM)은 복잡한 형상 제조 및 재료 비용 절감으로 인해 혁신적인 제품 생산 방법으로 각광을 받고 있다. 그 중에서도 압출적층조형(Fused Deposition Modeling, FDM) 공정을 통한 친환경 부품 제조는 의료 분야산업에서 많은 주목을 받고 있다. 따라서, 본 논문에서는 친환경 생분해성 재료인 Poly Lactic Acid(PLA)를 사용한 FDM 공정 실험을 수행하고 제작된 적층 시편에 대한 인장 시험을 적용하여 주요 FDM 공정 변수인 적층 두께, 적층 방향, 적층 충진량이 인장 시편의 기계적 성질에 미치는 영향을 정량적 및 정성적으로 분석하고 이를 극대화하는 각 공정 변수의 최적값을 도출하였다. Recently, additive manufacturing (AM) technology, also known as 3D printing technology, has attracted attention as an innovative production method to fabricate functional components having complex shapes with saving materials. In particular, a fabrication of poly lactic acid (PLA) parts through a fused deposition modeling (FDM) technique has attracted much attention in the medical field. In this paper, an experimental study on the identification of dominant process parameters influencing mechanical properties of PLA parts fabricated by the FDM process is conducted, and their optimal values for maximizing the mechanical properties are obtained. Three process parameters are considered in this research, namely, layer thickness, a part orientation and in-fill. It is known that thin layer thickness, part orientation diagonal to the tension direction, and full in-fill are optimal conditions to maximize the mechanical properties.
고속비상체 충돌에 의한 콘크리트의 손상예측식(수정 NDRC) 적용을 위한 섬유보강계수의 검토
김정현(Kim, Jung-Hyun),김규용(Kim, Gyu-Yong),김홍섭(Kim, Hong-Seop),한상휴(Han, Sang-Hyu),남정수(Nam, Jeong-Soo),유재철(Yoo, Jea-Chul) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.1
Elements of penetration and scabbing in fracture behavior of concrete subjected to high-velocity impact are compressive strength and flexural-tensile strength respectively. Crack and scabbing of fiber reinforced concrete by high-velocity impact can be suppressed by improved flexural-tensile performance with bridging action of reinforcement fiber. However, since existing NDRC formula mainly considers properties of projectile, impact velocity, and compressive strength as parameter, it is difficult to predict scabbing limit thickness of fiber reinforced concrete with increase of flexural-tensile performance. Therefore, in this study, fracture depth, diameter, and scabbing limit thickness of steel and polyamide fiber reinforced concrete were evaluated by high-velocity projectile impact test, and fracture reduction coefficient according to fiber types and volume fraction was calculated. Also, scabbing limit thickness prediction method was presented by applying modified fracture reduction coefficient to NDRC formula. As results, scabbing thickness and diameter and scabbing limit thickness were suppressed with increasing volume fraction of fiber. Futhermore, it was possible to make accurate prediction for scabbing limit thickness of fiber reinforced concrete by applying modified fracture reduction coefficient to NDRC formula.