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CO<sub>2</sub> 레이저용접시 용접조건에 따른 플라즈마 방사신호의 특성연구
김종도,이창제,Kim, Jong-Do,Lee, Chang-Je 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.11
Today, implementation of the defect detection in laser welding has been researched for a long time, but most studies have been made around thin plate within $1{\sim}3mm^t$. Therefore, this study was measured and analyzed light emission signals of the induced plasma in $CO_2$ laser lap welding of $6mm^t$ Zn primer-coated steel, and based on this analysis, research made an investigation into possibility of monitoring in thick plate welding. It was been analyzing the measured signals by RMS and FFT processing, as a results, we were able to confirm definite difference of two signals between humping bead and sound bead. Thus, possibility of real time monitoring in $CO_2$ laser lap welding verified experimentally.
Jong-Hae Kim(김종해),Do-Cang Oh(오도창) 대한전기학회 2013 전기학회논문지 Vol.62 No.4
This paper considers the problem of robust stability for uncertain discrete-time interval time-varying delayed descriptor systems using any combinations of quantization and overflow nonlinearities. First, delay-dependent linear matrix inequality (LMI) condition for discrete-time descriptor systems with time-varying delay and quantization/overflow nonlinearities is presented by proper Lyapunov function. Second, it is shown that the obtained condition can be extended into descriptor systems with uncertainties such as norm-bounded parameter uncertainties and polytopic uncertainties by some useful lemmas. The proposed results can be applied to both descriptor systems and non-descriptor systems. Finally, numerical examples are shown to illustrate the effectiveness and less conservativeness.
소형 추력기의 성능 개선을 위한 액체 추진제 주입기 최적 설계 및 추진제 거동 연구
김기로(Kiro Kim),김수겸(Su-Kyum Kim),변도영(Do-Young Byun),이세민(Se-Min Lee),정강수(Kang-Su Jung),박수형(Soo-Hyung Park),김성균(Sung-Kyun Kim),유명종(Myoung-Jong Yu) 한국항공우주학회 2011 韓國航空宇宙學會誌 Vol.39 No.4
본 연구는 기존의 인젝터와 새로운 형태의 인젝터를 비교분석 함으로써 소형 추력기의 성농을 연구하였다. 기존의 인젝터는 볼록한 표면에 8개의 노즐로 구성되어 액체 추진제를 분사하는 형태로 제작되었다. 우리가 제안한 새로운 형태의 인젝터는 오목한 표면에 4, 5, 6, 8, 9개의 노즐로 구성된 충돌형 인젝터이다. 노즐의 구멍을 통해 분사되는 액체 추진제는 축 방향으로 한 점에서 부딪히게 설계되었으며, 이는 분사되는 액체 추진체의 입자를 더욱 세분화하여 사방으로 일정하게 분무할 수 있도록 하였다. 본 논문에서는 천산유체역학, 입자 유속계 및 고속 카메라를 이용하여 분무 가시화 및 인젝터의 성능을 연구하였다. This work studies the performance of an injector for a monopropellant thruster, comparing a conventional and new injector types. The conventional injector consists of 8 nozzles on a convex surface allowing the jet to be diverged. The new injector, we suggested, is an impinging type with nozzle holes on a concave surface. The fuel streams through the nozzle holes are collide at a point on an axial direction, which allow to atomize the liquid streams and to spray more uniformly along circular direction. The performance of the injectors is investigated by using computational fluid dynamics, particle image velocimetry and high speed camera visualization.
조선용 아연코팅강판의 $CO_2$ 레이저 겹치기 용접시 인프로세스 측정신호와 용접결함과의 관련성
김종도,이창제,이재범,서정,Kim, Jong-Do,Lee, Chang-Je,Lee, Jae-Bum,Suh, Jeong 한국레이저가공학회 2010 한국레이저가공학회지 Vol.13 No.3
The in-process monitoring of $CO_2$ welding of Zn-coated steel plates has been studied and compared with that of conventional thin plates. Relationships between weld defects and plasma emission signals were evaluated in laser lap joint of thick Zn-coated steel. According to the study, weld defects were found to increase with Zn content. As a result, measured plasma emission signals also decreased. In case of plate with $15{\mu}m$-thick Zn-coated layer, defects caused by evaporation of Zn could, therfore, controled by gap of 0.1mm, resulting in a stable emission signals. However, the amplitude of signals fluctuated very widely. Variation of amplitude sould be limited in 3-8V by FFT smoothing.
레이저 열원을 이용한 보론강 및 핫스탬핑강의 용접특성에 관한 연구 (Ⅱ)
김종도(Jong Do Kim),최소영(So Young Choi),박인덕(In Duck Park) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.12
핫스탬핑 공정은 고강도의 강을 얻을 수 있는 방법으로써, 일반적으로 보론강을 오스테나이트 온도까지 가열한 후, 성형과 냉각을 통해 제품을 생산한다. 열처리된 보론강은 1500MPa 이상의 강도를 가지기 때문에 경량화와 안전성을 동시에 향상시킬수 있는 특징이 있다. 뿐만아니라 우수한 성형성으로 인한 치수정밀도가 기존 강판대비 90 % 이상 향상되어 우수한 성형품질을 확보할 수 있는 장점도 있다. 따라서 본 연구에서는 디스크 레이저를 사용하여 핫스탬핑 강판의 맞대기 및 겹치기 용접을 실시하여 용접특성을 파악하였다. 실험결과, 맞대기 용접에서는 맞댄면의 갭에 영향으로 인해 겹치기 용접과 비교하여 더 빠른 속도에서도 완전 용입을 얻을 수 있었으며, 모든 용접부에서 열영향부에서 화이트밴드가 관찰되었다. Hot-stamping is a method of obtaining ultrahigh-strength steel by simultaneously forming and cooling boron steel in a press die after it has been heated at 900 °C or above. After heat treatment, boron steel has a strength of 1500 MPa or more. This material ensures a high level of quality because it overcomes the spring-back phenomenon, which is a problem associated with high-strength steel materials, and the degree of dimensional precision is improved by 90 or more because of the good formability compared with existing types of steel. In this study, the welding characteristics were identified through the butt and lap welding of hot-stamped steel using a disk laser. Full penetration was obtained at a faster speed with butt welding compared to lap welding, and a white band was observed in every specimen.
김은란 ( Eun Ran Kim ),성기철 ( Ki Chul Sung ),전창욱 ( Chang Uk Chon ),권창희 ( Chang Hee Kwon ),고영율 ( Young Lyul Koh ),이현종 ( Hyun Jong Lee ),박성근 ( Sung Kun Park ),이도영 ( Do Young Lee ),윤지호 ( Ji Ho Yun ),김병진 ( By 대한내과학회 2006 대한내과학회지 Vol.70 No.6
목적: 미세단백뇨는 당뇨병이나 고혈압과 무관하게 심혈관 질환 발생 및 사망의 독립적 예후인자로 인식되고 있으나, 국내에서는 이와 관련된 보고가 부족한 실정이다. 본 연구는 국내 성인 건강검진 수진자들을 대상으로 미세단백뇨의 유병률 및 미세단백뇨와 인슐린 저항성, 심혈관 질환의 위험인자들과의 연관성에 대해 알아보고자 하였다. 방법: 2004년 1월부터 12월까지 강북삼성병원에서 종합검진을 받은 수진자 중 고혈압, 당뇨 등의 기왕력이 없는 총 5,915명(남 Background: Microalbuminuria (MA) is independent predictor of cardiovascular disease and it cause mortality regardless of the presence of diabetes (DM) and hypertension (HTN). However, few published studies on this topic have been reported in Korea. Theref
$6mm^t$조선용 프라이머 코팅강판의 $CO_2$레이저 용접성( I ) - 프라이머 코팅조건과 갭 간극의 영향 -
김종도,박현준,Kim Jong-Do,Park Hyun-Joon 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.3
Recently the application of laser welding technology has been considered to shipbuilding structure. However, when this technology is applied to primer coated steel, good quality weld beads are not easily obtained. Because the primer-coated layer caused the spatter, humping bead and porosity which are main part of the welding defect attributed to the powerful vaporizing pressure of zinc. So we performed experiment with objectives of understanding spatter and porosity formation mechanism and producing sound weld beads in 6mmt primer coated steels by a $CO_2$ CW laser. The effects of welding parameters; defocused distance, welding speed, coated thickness and coated position; were investigated in the bead shape and penetration depth on bead and lap welding. Alternative idea was suggested to suspend the welding defect by giving a reasonable gap clearance for primer coated thickness. The zinc of primer has a boiling point that is lower than melting point of steel. Zinc vapor builds up at the interface between the two sheets and this tends to deteriorate the quality of the weld by ejecting weld material from lap position or leaving porosity. Significant effects of primer coated position was lap side rather than surface. Therefore introducing a small gap clearance in the lap position, the zinc vapor could escape through it and sound weld beads can be acquired. In conclusion, formation and suspension mechanism of the welding defects was suggested by controling the factors.
김종도(Jong-Do Kim),윤문철(Moon-Chul Yoon) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
In the paper, a new end-milling force model was suggested by considering run-out and it was compared with real case of end-milling process. An experimental coefficient modelling method was used for the formulation of theoretical end-milling force by considering the specific cutting force coefficient. The end-milling force mechanics with run-out was presented for theoretical force model in simple end-milling operations by considering the geometric shape of the workpiece part.
김종해(Jong-Hae Kim),오도창(Do-Cang Oh) 대한전기학회 2012 전기학회논문지 Vol.61 No.3
In this paper, we consider the problem of a robust passive filtering with low-order for discrete-time singular systems with polytopic uncertainties. A BRL(bounded real lemma) for robust passivity with a dissipativity of discrete-time uncertain singular systems is derived. A low-order robust passive filter design method is proposed by new reduced-order method and LMI(linear matrix inequality) technique on the basis of the obtained BRL. Finally, illustrative examples are presented to show the applicability of the proposed method.