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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.
질화규소 세라믹의 레이저 예열선삭에 관한 연구 (III) - SSN 및 HIPSN의 예열선삭시 절삭력 및 공구수명의 특성 -
김종도,이수진,강태영,서정,이제훈,Kim, Jong-Do,Lee, Su-Jin,Kang, Tae-Young,Suh, Jeong,Lee, Jae-Hoon 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.6
Generally, ceramic material is very difficult to machine due to high strength and hardness. However, ceramic material can be machined at high temperature by plastic flow as metallic material due to the deterioration of the grain boundary glassy phase. Recently, a new method was developed to execute cutting process with CBN cutting tool by local heating of surface with laser. There are various parameters in LAM because it is a complex process with laser treatment and machining. During laser assisted machining, high power results in reducing of cutting force and increasing tool life, but excessive power brings oxidation of the surface. The effect of laser power, feed rate, cutting depth and etc. were investigated on the life of cutting tool. Chips were observed to find out suitable machining conditions. Chips of SSN had more flow-types than HIPSN. It means SSN is easier to machining. The life of cutting tool was increased with increasing laser power and decreasing feed rate and cutting depth.
질화규소 세라믹의 레이저 예열선삭에 관한 연구 (I) - 공정변수에 따른 질화규소의 예열특성 및 산화거동 -
김종도,이수진,서정,이제훈,Kim, Jong-Do,Lee, Su-Jin,Shu, Jeong,Lee, Jae-Hoon 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.4
Silicon nitride is widely used as an engineering ceramics because it has high strength, abrasion resistance and corrosion resistance even at high temperature. However, machining of silicon nitride is difficult due to its high hardness and brittleness. Laser assisted machining(LAM) allows effective cutting using CBN tool by locally heating the cutting part to the softening temperature of YSiAlON using the laser beam. The effect of preheating depending on process parameters were studied to find out the oxidation mechanism. If silicon nitride is sufficiently preheated, the surface is oxidized and $N_2$ gas is formed and escapes from the material, thereby making the cutting process more advantageous. During laser preheating process before machining, high temperature results in strong oxidation which makes the bloating, silicate layers and micro cracks. Using the results of these experiments, preheating characteristics and oxidation behavior were found out.
질화규소 세라믹의 레이저 예열선삭에 관한 연구 (II) - 예열선삭된 SSN 및 HIPSN 질화규소 세라믹의 표면특성 -
김종도,이수진,강태영,서정,이제훈,Kim, Jong-Do,Lee, Su-Jin,Kang, Tae-Young,Suh, Jeong,Lee, Jae-Hoon 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.5
This study focused on laser assisted machining (LAM) of silicon nitride ceramic that efficiently removes the material through machining of the softened zone by local heating. The effects of laser-assisted machining parameters were studied for cost reduction, and active application in processing of silicon nitride ceramics in this study. Laser assisted machining of silicon nitride allows effective cutting using CBN tool by local heating of the cutting part to the softening temperature of YSiAlON using by the laser beam. When silicon nitride is sufficiently preheated, the surface is oxidized and decomposed and then forms bloating, micro crack and silicate layer, thereby making the cutting process more advantageous. HIPSN and SSN specimens were used to study the machining characteristics. Higher laser power makes severer oxidation and decomposition of both materials. Therefore, HIPSN and SSN specimens were machined more effectively at higher power.
CO₂ 레이저용접시 용접조건에 따른 플라즈마 방사신호의 특성연구
김종도(Jong-Do Kim),이창제(Chang-Je Lee) 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 1~3mm<SUP>t</SUP>. Therefore, this study was measured and analyzed light emission signals of the induced plasma in CO₂ laser lap welding of 6mm<SUP>t</SUP> 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 CO₂ laser lap welding verified experimentally.
아연코팅 강판의 CO₂ 레이저용접시 인프로세스 모니터링을 위한 측정신호와 용접결함과의 관련성 연구
김종도(Jong-Do Kim),이창제(Chang-Je Lee) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.10
본 연구에서는 조선용 6㎜ 아연코팅강판의 CO₂ 레이저 겹치기 용접시 발생하는 유기 플라즈마를 마이크로폰과 포토다이오드로 측정하였다. 이때 겹치기 갭간극에 따른 용접조건을 RMS한 신호와 비교분석하였다. 이를 통해 아연증발량이 증가함에 따라 RMS값도 증가하였으며, 겹침부의 조건에 따라 결함 발생시 RMS의 급격한 변화도 확인할 수 있었다. 또한 용접조건에 따른 Raw signal의 FFT값을 구한 후, 이때 구해진 주파수값을 밴드폭으로 설정하여 Raw signal을 필터링한 뒤의 RMS값을 용접비드와 대응하여 필터링하지 않은 RMS와의 차이점도 비교 분석하였다. 이를 통해 기존의 방법들보다 신뢰성 높은 In-process 모니터링이 가능함을 확인하였다. In this study, the plasma induced by CO₂ laser lap welding of 6t Zn coated steel used for ship building was measured using photodiodes and a microphone. Then, the welding phenomenon with gap clearance of lap joint was compared with RMS-treated signal. Thus, we found that intensity of the RMS-treated signal increased with Zn vaporization; further, the presence of defects results in rapid variations with the RMS value as a function of lap-joint parameters. Besides, the FFT value of the raw signal with variations of changing welding parameters was calculated, and then the calculated FFT frequency value was set as the bandwidth of digital filter for a more accurate in-process monitoring. The RMS values were acquired by filtering the raw signal. By matching the weld beads and the calculated RMS values, we confirmed that there is a strong relationship between the signals and the defects.
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.
김종도(Jong-Do Kim),윤문철(Moon-Chul Yoon) 한국생산제조학회 2010 한국공작기계학회 추계학술대회논문집 Vol.2010 No.-
An mode analysis of end-milling system was introduced using recursive parametric modeling analysis. Also, the numerical mode analysis of end-milling system with different conditions was performed systematically. In this regard, a recursive extended instrumental variable method(REIVM) modeling algorithm and the natural mode for real part and imaginary one was discussed. This recursive approach (REIVM) can be adopted for the on-line system identification and monitoring of an end-milling for this purpose. After experimental practice of the end-milling, the end-milling force was obtained and it was used for the calculation of FRF(Frequency response function) and mode analysis. Also, the FRF was analysed for the prediction of a end-milling system and its mode shape was acquired by solving the eigen-problem using recursive algorithm. Thus, these algorithm for the detection of natural modes of end-milling was successful in each condition. After numerical analysis of the responses, which is cutting force was conducted for the calculation of FRF and mode analysis.
$6mm^t$조선용 프라이머 코팅강판의 $CO_2$레이저 용접성 (II) - 레이저 용접현상의 동적거동과 기공 및 증발입자의 조성 -
김종도,박현준,Kim, Jong-Do,Park, Hyun-Joon 대한용접접합학회 2006 대한용접·접합학회지 Vol.24 No.2
It has been reported that good quality weld beads are not easily obtained during the $CO_2$ CW laser welding of primer coated plate. However, by introducing a small gap clearance in the lap position, the zinc vapor can escape through it and sound weld beads can be acquired. Therefore, this study examines for keyhole behavior by observing the laser-induced plasma and investigates the relation between keyhole behavior and formation of weld defect. Laser-induced plasma has accompanied with the vaporizing pressure of zinc ejecting from keyhole to surface of primer coated plate. This dynamic behavior of plasma was very unstable and this instability was closely related to the unstable motion of keyhole during laser welding. As a result of observing the composition of porosity, much of Zn element was found from inner surface of porosity. But Zn was not found from the dimple structure fractured at the weld metal. By analyzing of vaporizing element in laser welding, a component ratio of Zn was decreased by introducing a small gap clearance. Therefore we can prove that the major cause of porosity is the vaporization of primer in lap position. Mechanism of porosity-formation is that the primer vaporized from the lap position accelerates dynamic behavior of the key hole and the bubble separated from the key hole is trapped in the solidification boundary and romaines as porosity.