The Effect of Magnetic Fields for Laser Welding Process using Carbon Steel

이철구,이우람 한국정밀공학회 2013 International Journal of Precision Engineering and Vol.14 No.11

A Multi-physics numerical model was developed to investigate the influence of a steady magnetic field aligned perpendicular to the welding direction during partial penetration fiber laser beam welding of carbon steel(SCP1-S) in down hand position. Twodimensional fluid dynamics including phase transition and electromagnetic field partial differential equations were successfully solved with the finite element differential equation solver COMSOL Multiphysic 3.5. The use of magnetic fields to influence weld bead shape and dilution in laser welding of SCP1-S alloys was recently suggested. However, the interaction mechanisms between the SCP1-S melt and the magnetic field are not understood in detail yet, and consequently, the selection of process parameters is so far purely empirical. In this paper, recent results of a study to elucidate interaction mechanisms between a laser-induced melt pool and a magnetic field will be reported and discussed. Based on analytical models for the main potential interaction mechanisms, the relevance to typical welding conditions was assessed. The flow pattern in the melt as well as the weld bead geometry was significantly changed by the induced Lorentz force distribution in the liquid metal. The governing mechanisms identified were implemented into a COMSOL model for laser welding and the effect of the magnetic field on the resulting melt flow was investigated. To validate the results, welding trials were performed on a model system allowing to easily visualizing the effect of melt flow on melt bead dynamics using optical microscopy.

축열식 열원시스템 적용에 의한 전력부하 평준화의 경제성 검토

이철구 한국 지열 · 수열에너지학회 2019 한국지열에너지학회논문집 Vol.15 No.1

Reducing global warming potential has become important, and as one of those methods for reducing it, economic evaluation by applying ice thermal storage air conditioning system was performed. The floor area and height of the subject building was assumed 5,000 m2 and 20 m. Absorption chillerheater system and air source heat pump system was used for comparing to the subject system, and payback period method was used to perform economic evaluation. Although the running cost of ice thermal storage system is reduced compared to two systems, the ratio is not significant compared to the increase of initial construction expenses, and payback period was calculated to be about 7.7 and 79.3 years. However, the heat storage system should be approached from the viewpoint of long term rather than the economic standard in the present standard.

冷間壓接의 熔接過程에 對한 考察

李喆求 서울産業大學校 1987 논문집 Vol.26 No.1

The welding process is assumed to be achieved by four fundamental mechanisms: Plastic deformation, Creep deformation, interface diffusion and Volume diffusion. The experimental results based on this model makes it possible to understand quantitatively the effects of Welding temperature, Welding pressure, Welding time, roughness of faying Surface on the Welding process. It is found from the results that the deformation mechanisms tend to be dominant with increasing temperature and decrease roughness.

초음파 용접을 이용한 전선의 접합

이철구,황병주,허인호 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.4

In this study, the purpose finds out the best welding conditions for bonding of electric wire by ultrasonic welding. The material was plastic-insulating low-voltage cables for automobiles. The experiment varied the values of welding time and welding pressure and fixed the values of amplitude and energy. With the facts, the best condition for ultrasonic welding to achieve bonding exactly is gained according to the size of the cross-sectional area of the cable, and the adhesive intensity is greatly influenced by the variables of welding time and weld-ing pressure. Also when the welding time and welding pressure increase as the cross-sectional areas of the cable increase, the welding result is gained exactly.

常溫壓接에서 酸化皮膜의 影響에 관한 硏究

李喆求 서울産業大學校 1986 논문집 Vol.24 No.1

This paper is studied about the influence of oxidized films on weldability in cold pressure welding. In preceding studies, the principal foci of the studies about pressure welding were considered several factors (surface manufacturing methods, surface roughness, pressure welding speed and surface temperature). But the influence to the growth of oxidation have hardly know well. So the purpose of this paper consists in solving the question above and proposing the optimal states of the pressure welding. Therefore the results obtained is as the following; When the oxidation time is within about 2 minutes, the bonding strength is very good after surface manufacturing of the neighboring to be bonded. The more surfaces are fine, the more bonding strength is excellent. Above all, the optimal condition of cold pressure welding is the state that the characteristic value is 38% with smooth surface and without oxidation.

磁粉探傷法에 關한 硏究

李喆求 서울産業大學校 1982 논문집 Vol.17 No.1

Magnetic Particle testing method is a kind of non destructive testing to detect surface defect on ferro Magnetic materials. This study was tried to establish the relation between force of effect magnetic field and detected crack depth on the welded structure. We obtained detecting performance equation ?? for force of effective magnetic field be obtained from a magnetic characteristic curve. Inspection of welded structure distinguished Application to Magnetic particle testing method.

熱交換器의 表面條件에 對한 硏究

李喆求 서울産業大學校 1980 논문집 Vol.13 No.1

本 硏究에서의 解析은 같은 크기의 表面을 갖는 매끈한 관과 거칠은 관을 熱交換器에 적용시킬때 거칠은 表面을 가지고 있는 管이 훨씬 유용성이 있다는 것을 입증한다. 거친 표면을 가진 熱交換器의 잇점으로는 1. 熱交換器의 容量을 증가시키고, 2.摩擦에 의한 손실을 감소시킬 수 있으며, 3. 열교환기의 크기를 축소시킬 수 있다는 것이다. 熱交換器의 實驗에는 사용되어 온 一般的인 熱傳達 關係式을 基礎로 거친 表面의 熱交換器에 對한 실제적인 적용에 대하여 고찰하였다. 本 實驗 結果를 表示하는 graph 에서 매끈한 表面을 갖는 管과의 比較로부터 거친 表面을 갖는 형(repeated rib 의 경우) 이 實際的인 熱交換에 있어서 우수하다는 것을 나타낸다. 本 論文에 repeated rib 을 갖는 傳熱面에 대한 結果가 圖解되였으며, 이 圖表들은 이와같은 거칠은 表面을 使用하므로서 熱交換器의 性能을 증진시킬 수 있다는 것을 보여준다. 또한 repeated rib 을 갖는 傳熱面에 대한 熱傳達 關係式과 마찰 손실에 대한 式들은 기하학적으로 유사한 粗度를 갖는 다른 形態의 傳熱面에 대한 data를 解析하는데도 使用될 수 있을 것이며, 說計面에서도 여러가지 형태를 갖는 거친 表面에 대해서도 應用될 수 있을 것이다. The study on surface condition in heat exchanger. Equations are developed to define the performance advantage of roughened tubes in heat exchanger design relative to smooth tubes of equal diameter. Three rough tube applications are presented; 1. To obtain increased heat exchanger capacity. 2. To reduce the friction power and 3. To permit a reduction of heat transfer surface area. A heat exchanger design procedure is developed for each application and is based on the use of previously developed generalized heat transfer and friction corrections for rough surface. The graphical results of example solutions are presented for the case of "repeated-rib" roughness. These graphs show the heat exchanger performance improvements offered by this roughness type, relative to smooth tubes. Because the heat transfer and friction correlations used for the "repeated-rib" roughness can be used to correlate the data of other type of geometrically similar roughness the design procedure is applicable to other types of roughness.

常溫壓接에서 表面粗度와 熔接變形度에 대한 考察

李喆求 서울産業大學校 1985 논문집 Vol.22 No.1

Roughness of the surface to be weaked is one of the important factors affecting the weldabilities on the pressure weling. The purpose of this study is to investigate the influences of the surface roughness upon the welding process and the weldability of pressure welds, using Aluminium AA1050 plates treated by various surface polishing. The results obtained are as following: 1. The optimal welding deformation is about 38(%)-42(%) in cold pressure weld. 2. The grinding work on the weld surface is superior than milling and paper polishing. 3. Weld pressure must beyond in order 0.5(㎏/㎟) that the bond may be achieved.

접착제와 초음파용접을 이용한 플래스틱의 접합

이철구,조수현 서울産業大學校 2005 논문집 Vol.54 No.1

This study was to find the best adhesive condition compare mechanical property in plastic resin of polyethylene and polyamide adhesion. Following results were acquired with varing welding time and welding pressure. Satisfactory adhension was executed in ultrasonic welding for the same materials of polyethylene and polyamide. The best welding conditions of welding time 1 second, welding pressure 250KPa for polyethylene welding, 2 second and 350Kh for polyamide welding. Welding time and welding pressure were inclined to increase according the rise of materials strength. Dissimilar materials were adhered when adhesion and ultrasonic welding were performed at the same time.

다시 사이좋은 카페를 논하다

이철구 예수살이공동체 2017 산위의 마을 Vol.32 No.-