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레이저 분말적층 방식을 이용한 금속 3D 프린터 개발 및 티타늄 합금 부품 제조공정 최적화
정원종,권영삼,김동식,Jeong, Wonjong,Kwon, Young-Sam,kim, Dongsik 한국레이저가공학회 2015 한국레이저가공학회지 Vol.18 No.3
A 3D printer based on laser powder deposition (LPD), also known as DED (direct energy deposition), has been developed for fabricating metal parts. The printer uses a ytterbium fiber laser (1070nm, 1kW) and is equipped with an Ar purge chamber, a three-dimensional translation stage and a powder feeding system composed of a powder chamber and delivery nozzles. To demonstrate the performance of the printer, a tapered cylinder of 320mm in height has been fabricated successfully using Ti-6Al-4V powders. The process parameters including the laser output power, the scan speed, and the powder feeding rate have been optimized. A 3D printed test specimen shows mechanical properties (yield strength, ultimate tensile strength, and elongation) exceeding the criteria to employed in a variety of Ti alloy applications.
고등학교 지구과학I ‘아름다운 한반도’ 단원 STEAM 교수학습활동의 효과 분석
정원종(Won-Jong Jeong),위수민(Soo-Meen Wee) 한국교원대학교 뇌기반교육연구소 2019 Brain, Digital, & Learning Vol.9 No.3
It is the purpose of the study to conduct a survey analysis of students reactions found after the design and application of STEAM (Science Technology Engineering Arts Mathematics) for the unit of ‘The Beautiful Korean Peninsula’ of Earth Science I for high schools and to suggest a teaching and learning activity to promote students’ involvement and interest into science classes. In order to analyze the effects of students’ involvement into science classes, every group of two students obligatorily present their task product, which brought a higher class involvement for there was no one who did not participate in the presentation. As the option for selecting a study theme and a method for presenting it was given students, which makes them take the lead of the class, the level of the preference to the class was found higher. And it was allowed for them to give positive feedback to their classmates, which resulted in a positive thinking on the science class and brought an improved consequences on their involvement and preferences to the class as well. In addition, it was also confirmed that their burden of science classes might be reduced and their preference to the class could be increased because the STEAM class was not reflected to their grades.
정원종(Wonjong Jung),최성목(Sung Mok Choi),김정택(Jung Taek Kim),김원정(Wonjung Kim),김호영(Ho-Young Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
We present the result of a combined experimental and theoretical investigation of granular drag reduction induced by rotation of self-burrowing seeds of Pelargonium species. The seed dispersal unit of Pelargonium has a hygroscopically responsive awn which reversibly coils and uncoils in response to the change in environmental humidity. When the awn tip is supported by an external object, the hygroscopic deformation of the awn gives the seed a thrust and rotation against the soil. Such coiling-uncoiling motion enables the seed to dig into the soil. We find that the rotation of the seed significantly reduces the granular drag, which greatly facilitates its self-burrowing. To elucidate and quantify such granular drag reduction, we experimentally measure the granular resistance for rotating intruders. We then develop a partial slip model that explains how the rotation of the seed extenuates the effective area where the granular hydrostatic pressure acts. Our work reveals that the rotation of the self-burrowing seed is essential to the survival and successful breeding.
티타늄 합금 부품 제조를 위한 금속 3D 프린터 개발 및 공정 최적화
정원종(Wonjong Jeong),권영삼(Young-Sam Kwon),김동식(Dongsik Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
To fabricate Ti alloy parts, a 3D printer based on laser powder deposition (LPD), powder feeding method, has been developed. The printer consists of a ytterbium fiber laser (1070 nm, 1 kW), an Ar purge chamber, a three-dimensional translation stage and a powder feeding system with a powder chamber and powder delivery nozzles. A tapered circular cylinder of 320 mm in height and a tapered square cylinder of 160 mm in height have been fabricated to prove the performance of the printer using Ti-6Al-4V powders. In terms of powder efficiency, Optimization is performed using the process parameters like the laser output power, the scan speed, and the powder feeding rate. The results of tensile test and composition analysis using test specimen fabricated by LPD show that the requirements of Ti alloy are met.