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최적구조변경법에 의한 자동차 엔진 블록의 중량최소화에 관한 연구
길병래 한국마린엔지니어링학회 1998 한국마린엔지니어링학회지 Vol.22 No.4
Recently to develop an automobile with better properities many researches and investments have been executed. In this paper we intend to improve the automobile properties by reducing the weight of the engine without changing the dynamic characteristics. At first the vibration analysis by the Substructure Synthesis Mehtod and the exciting test of the engine model performed to confirm the reliability of the analyzing tools. And the weight minimiza-tion is performed by the Sensitivity Analysis and the Optimum Structural Modificationl. To decrease the engine weight ideally the weight of the parts with the low sensitivity is to cut mainly and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with the high sensitivity. As actually the mathematical unique solution for the homogeneous problem(i. e. 0 object func-tion problem)does not exist we redesign the engine block with much thinner initial thickness and recover the natural frequencies and natural modes of original structure by the sensitivity analy-sis and then observe the Frequency Response Function(FRF) for the interesting points. In this analysis the original thickness of the engine model is 8mm and the redesigned initial thicknesses are 5mm and 6mm, And the number of the interesting natural frequencies are 1, 2, 3, 4 and 5 respectively.
조선용 프라이머 코팅강판의 $CO_2$ 레이저 용접에 있어서 프라이머 코팅 조건과 갭(Gap) 간극의 영향
길병래,장지연,김종도 한국마린엔지니어링학회 2004 한국마린엔지니어링학회지 Vol.28 No.1
The spatter and porosity could be occurred during$CO_2$CW laser welding of Primer- coated steel for shipbuilding. This study has suggested an alternative idea by examining of weld-defect formation mechanism. The primer-coated plate induced the spatter humping bead and porosity and these are main part of the welding defect. attributed to the powerful vaporizing pressure of primer attached on the base metal The zinc of Primer has a boiling point that is the lower temperature than melting point of steel zinc vapor will build 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. 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, we suggested the occurred and prevented mechanism of weld defects with searching the factor.
펄스 Nd:YAG 레이저를 이용한 모터용 스테이터 적층코어의 용접특성 [II] - 용접결함의 형성 메커니즘 규명 -
김종도,길병래,이창제,Kim Jong-Do,Kil Byung-Lea,Lee Chang-Je 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.5
Recently, there were some successful examples that the laser welding was introduced into production line. However, the spread of laser welding is not sufficient in many industries. There are several reasons why it is difficult to penetrate the laser welding into production lines. Because it is different from reflection, absorption and permeation of laser beam according to material and surface condition. Moreover, there are significant problems in processing such as absorption and scattering of beam by the induced plasma or plume. Therefore, understanding of mechanism on formation of weld defect in laser welding of the laminated core for motor is very important. In this paper, it was analyzed in terms of materials which was source of defect in laser welding and conventional arc welding. As a results of analysis, insulation coating film of the laminated core was judged to main factor of weld defect. it could be well aware as tracing carbon volume, and it was deduced that weld defect by insulation coating film was caused by difference of mechanism between the two heat sources.
구형용기의 하부면 냉각에 의한 해수 동결거동의 기초적 연구
김명준,길병래,김명환 한국마린엔지니어링학회 1997 한국마린엔지니어링학회지 Vol.21 No.5
The most important factor for the desalination system is the fresh water production cost dependent upon the possible energy source which should be obtained easily and with low price. Recently in Korea the demand of LNG, as a cheap and clean energy which does not cause an environmental problem, has sharply been increased. In general, LNG is storaged in a tank as a liquid state below -162 'C. When it is serviced, however, the LNG absorbs energy from a heating source and transforms to the gaseous state with high pressure. During this process a huge amount of cold energy accumulated in LNG is wasted. This waste cold energy can be utilized for producing fresh water from sea water using a sea water freezing desalination system. In order to develop a sea water freezing desalination system and to establish its design technique, a qualitative and quantitative data regarding the freezing behavior of sea water is needed in advance. The goal of this study, therefore, are to reveal the freezing mechanism of sea water, to measure the freezing rate, and to investigate the freezing heat-transfer characteristics. The experimental results help to provide a general understanding of the sea water freezing behavior in a Rectangular vessel cooled from below.
김종도,길병래,김종호,김영식 한국레이저가공학회 2001 학술발표대회 Vol.2001 No.1
저자들은, 고품질•고정도의 레이저 용접부를 얻기 위해, 레이저 용접현상에 대한 분광학적 해석과 직접적인 관찰에 의해 용접결함의 형성 메커니즘을 규명하고, 방지책을 확립하는 것을 목적으로 하여 일련의 연구를 행하고 있다. 앞의 보고에서는, 펄수 YGA레이저 용접시에 유기하는 플라즈마와 용융 풀(molten pool) 및 키홀의 거동을 초고속 계측 시스템을 이용하여 관찰하고, 유기 플라즈마와 키홀 거동과의 관련성을 명확히 규명하였다. 본 보고에서는, 용접부의 깊은 용입특성과 기공(porosity) 등 용접결함의 생성과 방지에 미치는 레이저 펄스 파형의 영향에 관하여 조사하고, 그 때 유기되는 프라즈마 및 키홀거동을 고시간 분해능으로 리얼타임으로 동시계측하여 가시화를 꾀하고, 기공의 생성•방지 메카니즘에 관한 지견을 얻었다.
공기부양선의 추진 및 부양축계 종진동 해석에 관한 연구
손선태,길병래,김정렬,Son, Seon-Tae,Kil, Byung-Lea,Kim, Jung-Ryul 한국마린엔지니어링학회 2007 한국마린엔지니어링학회지 Vol.31 No.6
In this study, axial vibration analysis has been conducted on a propulsion and lift shafting system for an air cushion vehicle using ANSYS code. The shafting system is totally flexible multi-elements system including wood composite material of air propeller. aluminum alloy of lift fan and thin walled shaft with flexible coupling. The analysis calculated the axial natural frequencies and mode shapes of the shafting system taking into account an equivalent mass-elastic model for shafting system as well as the three-dimensional models for propeller blade and fan impeller. Such a flexible shafting system has very intricate vibrating characteristics and especially, axial natural frequencies of flexible components such as propeller blade and impeller of lift fan can be lower to the extent that causes a resonance in the range of operating revolution. The results for axial vibration analysis are presented and compared with the results of axial vibration test for lift fan conducted during Sea Trial.
순티타늄판의 Nd:YAG 레이저 용접성에 관한 연구(III) - 에지 용접 특성 -
김종도,길병래,곽명섭,송무근,Kim, Jong-Do,Kil, Byung-Lea,Kwak, Myung-Sub,Song, Moo-Keun 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.6
Titanium and titanium alloy can be reproduced immediately even if oxide films($TiO_2$) break apart in sea water. Therefore, since titanium demonstrates large specific strength and outstanding resistance to stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion in sea water environment, it has been widely applied to heat exchanger for ships. In particular, with excellent elongation, pure titanium may be deemed as optimal material for production of heat exchanger plate which is used with wrinkles formed for efficient heat exchange. Conventional plate type heat exchanger prevented leakage of liquid through insertion of gasket between plates and mechanical tightening by bolts and nuts, but in high temperature and high pressure environment, gasket deterioration and leakage occur, so heat exchanger for LPG re-liquefaction device etc do not use gasket but weld heat exchanger plate for use. On the other hand, since welded plate cannot be separated, it is important to obtain high quality reliable welds. In addition, for better workability and production performance, lasers that can obtain weldment with large aspect ratio and demonstrate fast welding speed even in atmospheric condition not in vacuum condition are used in producing products. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through quantitative analysis of oxygen and nitrogen and measurement of hardness as fundamental experiment for the evaluation of titanium laser welding, and evaluated the welding performance and mechanical properties of butt welding. This study welded specimens in various conditions by using laser and GTA welding machine to apply edge welding to heat exchanger, and evaluated the mechanical strength through tensile stress test. As a result of tensile test, laser weldment demonstrated tensile strength 4 times higher than GTA welds, and porosity could be controlled by increasing and decreasing slope of laser power at overlap area.
심일환,송재욱,길병래,김정렬,김창제,Sim, Il-Hwan,Song, Jae-Uk,Gil, Byeong-Rae,Kim, Jeong-Ryeol,Kim, Chang-Je 한국항해항만학회 2001 한국항해학회지 Vol.25 No.3
In the recent years, major ship registers have demanded improved safety on the hull stress of large bulk carriers which are on navigation or cargo handling in harbour. Under these circumstances, a system that monitors hull stress and ship condition is being more and more important. If efficient and appropriate navigational information is given, safety of navigation would be greatly improved. The major ship registers of the globe are investing a great effort on the development of a system that monitors the hull stress of ship. Using this system, information of hull stress and ship motion is given to the users and also the data is stored on the external data storage system simultaneously. Through this study, a software that monitors hull stress was developed. Not only can randomized input-data of the standard hardwares be applied to the system, but also this system can be operated on and applied to real hardware systems.