• Journal of Power System Engineering
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• v.14 no.3
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• pp.58-63
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• 2010

A laser beam welding and an electric arc welding were combined, and the positive points of each welding method are drawn such as high speed, low thermal load, deep penetration, and high productivity. The fiber laser-MIG conjugated welding. namely the hybrid welding has been studied mainly for the automation industry of a pipeline welding. In this study, the MIG welding was combined with a fiber laser welding to make up the hybrid welding. The weld shapes, microstructures and mechanical properties for weld zones after the hybrid welding or only fiber laser welding were investigated on the 700 MPa grade Ultra Fine Grained(UFG) high strength steel. The amount of acicular ferrite in weld metals and HAZ(heat affected zone) was observed larger after hybrid welding compared with after only laser welding. The Vickers hardness of the top area of the fusion zone after fiber laser welding was higher compared with after hybrid welding.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.9
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• pp.931-942
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• 2013

In this study, we analyzed and compared the ultrasonic welding with the laser welding for the pure aluminium thin plates in a series of secondary lithium-ion batteries which are currently being produced by the ultrasonic welding; and performed the experiment for the purpose of the preceding study to replace the ultrasonic welding method with the laser welding method. As a result, the weld width of ultrasonic welding was 5mm, but that of laser welding was about 1~1.5 mm. As a result of tension test, the tensile strength was high when the pulse duration hour was short at the low peak power, while the high tensile strength was achieved when the pulse duration hour was long at the high peak power. The value of tensile strength was higher in the ultrasonic welding while the laser welding showed a maximum 45% better result as for the welding width.

• Journal of Welding and Joining
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• v.28 no.1
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• pp.54-59
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• 2010

Ship Blocks are assembled by welding, and among them, welding between large blocks (Pre-erection stage) is used as feature of butt. In this process, local material has a experience of thermal cycle and become finally shrunk. As for inconsistency of shrunk weldments and adjacent regions, ship structure would be deformed locally and globally. Thermal distortion analyses are done for control of these processes, and methodologies capable of ship block size among them are using 2-D shell element in FEM. A shell element takes charge of plate, so it has its thickness which is important for angular distortion by welding. By the way, a butt-welding consists normally of several passes, and weldment thickness are different at each pass. If a calculated final one-time welding shrinkage is acting on the shell element whose thickness is same as it of plate, then deformation value must be underestimated. This research developed a methodology that total deformation after multi-pass welding can be analyzed by one time at shell element having original thickness of its plate. We use the SDB thermal distortion analysis method and verified by several experiment. The both experimental and analysis results showed good agreements.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.77-79
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• 2006

To achieve high productivity of assembly hull blocks, it is important to predict welding deformations accurately and to apply these data to the production planning. In the deformation analysis of hull block, simplified methods (elastic analysis) such as inherent method, equivalent loading method and local & global approach are usually used instead of thermal-elastic-plastic analysis because of calculating time and cost. To be much more practical, these simplified methods should consider gravity effect of plate and contact condition between the plate and the positioning jig. In this research, using finite element method, practical predicting method for the welding deformation of the curved hull blocks with considering welding sequence, gravity effect and contact condition is proposed.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.17-19
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• 2005

To achieve high productivity of assembly hull blocks, it is important to predict welding deformations accurately and to apply these data to the production planning. In the deformation analysis of hull block, simplified methods (elastic analysis) such as inherent method, equivalent loading method and local & global approach are usually used instead of thermal-elastic-plastic analysis because of calculating time and cost. To be much more practical, these simplified methods should consider gravity effect of plate and contact condition between the plate and the positioning jig. In this research, using finite element method, practical predicting method for the welding deformation of the curved hull blocks with considering welding sequence, gravity effect and contact condition is proposed.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.172-174
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• 2006

Nowadays, a Spot Welding system has been widely used in all kinds of industries and the common control method of the systeme is a simple current control using SCR. But, that kind of system is less effective than a current control method using inverter. So, it is constantly proposed that an improvement of hard ware and control method of spot welding system in compliance with technological advancement in power electronics. This paper deals with spot welding system using inverter. Especially, it deals with hard ware structure, features and output characteristics.

• Journal of Welding and Joining
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• v.35 no.1
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• pp.49-54
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• 2017

In this study, the volumetric heat source in electron beam welding (EBW) is modeled through finite element method taking advantage of ABAQUS software package. Since this welding method is being applied in plates with different thicknesses and also considering that residual stresses reduce the strength of these weldments, the effect of thickness in the distribution and magnitude of residual stresses after welding is studied. Regarding the vast application of Inconel 706 super-alloy in aerospace industries, this material was selected in the current research. In order to validate the finite element model, the obtained results were compared to those of other researchers in this area, and good agreement was observed. The simulation results revealed that increase in the plate thickness leads to increase in the residual stresses. In addition heat treatment in the base metal (before welding) increases the residual stresses significantly.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.349-354
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• 2002

Stud penetrate welding is an important item of composite floor in modern steel structure, especially in high-rise buildings. But it is difficult to get satisfied welding quality due to all kinds of factors. In this paper, the author put forward a new welding procedure named method of energy control through analysis and comparison of the wave curves of stud welding based on large amount of experiments and tests in laboratory and construction areas. The use of this welding procedure in some large engineering in recent years proved that this method is effective and practicable

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.1-10
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• 2008

Residual stress caused in the weldments with high restraint force are often during welding observed in the weldments of large size nozzles or radial tanks. The reason is that quantitative analysis about thermal stresses during welding is lack for this weldments. To verify Finite Elements Method(FEM) theory, the temperature was measured with thermocouple in a real time in this paper. Also analysis of the thermal stress for welding condition is performed by ABAQUS program package on various welding condition in 304 stainless steel butt welding.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.10
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• pp.571-578
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• 1999

Current waveform control of pulse MAG welding power source is studied so that welding of thin plates may obtain high speed and improved performance. In this paper, waveform control method is proposed, digital controller using DSP is able to control the current waveform precisely. High speed welding of thin plates using pulse MAG welding method is made possible. Performance test for 1.2mm thin plates is carried out, output waveform and welding performance is analyzed.