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3D 적층 STS316L 소재의 저항 점용접 특성 평가
김세현(SeHyeon Kim),김민규(Min-Gyu Kim),황인성(In-Sung Hwang),김동윤(Dong-Yoon Kim),김영민(Young-Min Kim),박지용(Jiyong Park),유지영(Jiyoung Yu) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.11
최근 다양한 산업에서 기존 가공방식으로는 제작이 어려운 복잡형상을 3D프린팅 방식으로 제작하는 사례가 늘어나고 있다. 특히, 위상 최적화를 통한 형상 제작을 통하여 무게를 감소시키고, 부품 일체화를 통해 기존 부품 용접부의 내구성 문제를 해결할 수 있어 주목을 받고 있다. 하지만, 이러한 장점에도 불구하고, 3D프린팅 방식은 아직 대형 부품을 제작하는데, 재료 및 공정의 한계를 보이고 있어 산업 부품을 제작하기가 적합하지 않다. 이에 일부 주요한 부품을 3D프린팅 기술로 제작하고 대형 부품에 용접하여 제품을 완성하는 기술에 대한 필요성이 대두되고 있다. 따라서 본 연구에서는 대표적인 3D 적층 STS316L과 STS316L 판재 소재에 대하여 각각 동종 소재 조합으로 저항 점용접을 진행하여 3D프린팅 부품의 용접성을 비교하는 연구를 수행하였다. 전극 가압력은 350 kgf로 고정한 후, 용접 전류, 용접 시간에 따라 용접을 진행하여 저항 점용접 로브를 도출 하였다. 용접 후, 단면 분석, 인장전단강도 시험, 조직 분석, 파형 분석을 통하여, 각 소재에 대한 저항 점용접성에 대해 평가를 진행하였다. 파형 분석은 용접 중 전류, 전압 신호를 측정하여, 동저항, 전력 신호를 도출 한 후, 거동에 대한 분석을 진행하여 3D프린팅 공정의 용접성을 확인하였다.
해석요소 선택에 따른 주철제 맨홀 및 틀의 구조해석기법
이형욱(H. W. Lee),박근영(G. Y. Park),김덕원(D. W. Kim),김명호(M. H. Kim),김승중(S. J. Kim) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.10
Manholes are constructed on road in order to maintain water and sewage pipelines as an entering gate for related persons. Recently locking devices of a manhole have been developed to prevent lost or stolen of the manhole. In this study, stress analysis of a cast-iron manhole was carried out as a part of the lightweight design. Stress analysis according to the solid elements selection was conducted to search a proper the tetra element for applying to complicated geometry model. Maximum stress, the deflection at the center, and stress distribution were considered as main factors in the comparison. The result of the normal second-order tetra element(C3D10) was similar to that of the first-order hex element with incompatible mode(C3D8I) in this case.
전동 스크롤압축기의 운전rpm에 따른 냉동사이클의 성능에 대한 실험적 연구
이규선(Lee K. S.),이근안(Lee K. A.),이형욱(Lee H. Y.),이영선(Lee Y. S.),김정배(Kim Jeongbae) 한국태양에너지학회 2014 한국태양에너지학회 논문집 Vol.34 No.3
An experimental study was performed estimating COP(Coefficient of Performance) of air-conditioning cycle with inverter scroll compressor. All experiments were done for various compressor speeds from 1000∼4000 rpm and used the inverter controller called CANDy to change the compressor rpm. The air-conditioning cycle components in the apparatus were used as same with components of YF hybrid car. To estimate the COP, this study measured the temperature and pressure at inlets and outlets of compressor, condenser, and evaporator. And also measured the compressor input power using Powermeter. Through the experiments, the maximum error to estimate COP was shown about ±6.09% at 3500rpm. This study revealed that the condenser temperature and pressure were increased and the evaporator temperature and pressure were decreased with the increased compressor speed. And also, the COP was decreased with increased compressor speed. Those results can be used the basic and fundamental data to design the air-conditioning cycle with inverter scroll compressor.
POE 오일 나노유체의 열물성과 분산성 평가를 위한 실험적 연구
이규선(Lee K. S.),이근안(Lee K. A.),이종섭(Lee J. S.),이형욱(Lee H. Y.),박성준(Park S. J.),이영선(Lee Y. S.),김상훈(Kim S),장석필(Jang S. P.),김정배(Kim J) 한국태양에너지학회 2012 한국태양에너지학회 논문집 Vol.32 No.3
To apply the nanofluids into the general vapor compression cycle, basically have to know the thermal properties including thermal conductivity and dynamic viscosity. And needs to show the dispersion characteristics for various nanofluids and concentrations. So, firstly this study showed experimentally the thermal properties for various concentration (0.1%~0.7%, as mass balance) and temperature(20℃~40℃) on Al₂O₃, TiO₂ and CuO nanofluids using base fluid as POE oil that has used in the scroll compressor for various refrigeration system. From the results, the dynamic viscosity of nanofluids was considerably changed from the base POE oil. And, the dispersion characteristics of various nanofluids using the simple methods like as analyzing the RGB value or measuring the sinking height of nanofluids were showed experimentally. Through the results, the dispersion characteristics of Al₂O₃, nanofluid was better than those of TiO₂, and CuO nanofluids not considering the real refrigeration cycle running conditions.
AZ31B 합금판재 성형관련 기초물성 실험 및 해석 연구
김세호(S. H. Kim),박기동(K. D. Park),장정호(J. H. Jang),김경태(K. T. Kim),이형욱(H. W. Lee),이근안(G. A. Lee),김기풍(K. P. Kim),이용신(Y. S. Lee) 한국소성·가공학회 2008 소성가공 : 한국소성가공학회지 Vol.17 No.7
In this paper, tension tests and formability tests are performed to construct a database related to mechanical properties and the formability of the AZ31B Mg alloy sheet. A forming test with a hemi-spherical punch is conducted at varying temperatures to establish a forming limit diagram. In order to verify the applicability of the analysis using the conventional flow hardening model, a finite element analysis is performed on the hemi-spherical punch forming process and the results are compared with experimental ones. The study investigates problems involving a computational analysis that does not consider flow softening of the magnesium alloy at elevated temperatures.