• Journal of Welding and Joining
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• v.34 no.5
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• pp.6-12
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• 2016

This study was performed bead welding of pure titanium by using fiber laser. Since titanium is very sensitive to oxidation and nitriding during welding, it is important to compose the shielding equipment compared with different material. Thus side and coaxial shield nozzle, rail and chamber type shielding equipment are widely used to protect effectively the weld during welding. Experiments were performed by changing nozzle angle and distance using side and coaxial shield nozzle. The bead colors of gold, brown, blue, purple and yellowish white were obtained by changing variables of shield nozzle, and then its weldability was investigated. As experiment result, sound and not brominated beads were formed when side nozzle angle and distance were respectively $45^{\circ}$ and 10 mm.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.159-162
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• 2000

Wrinkles and shape distortions are generated during the forming of B-pillar(or center pillar) which is a component of the automobile side-frame. The stretch flanging modes at the joining part of the B-pillar and the roof-rail or the side-still give rise to forming problems when taior-welded blanks are applied to the side-frames. The authors simplified B-pillar lower part to T shaped section to investigate the forming behaviors. Three of die step locations and two of blank types were tested to show the effects of weld line locations and edge conditions on he forming of tailor welded blanks. The heights of body wrinkles and the strain distribution in the stretch flanged area were measured and compared.

• Journal of Welding and Joining
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• v.24 no.4
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• pp.15-21
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• 2006

The aim of present study is to investigate the effect of welding parameters and heat treatment conditions on the formability of the $CO_2$ laser welded silicon steel sheet. It was found that there is optimum range of the heat input ($0.6{\sim}0.7kJ/cm$) and gap distance ($0.125{\sim}0.150mm$) for the high tensile strength and the avoidance of the fracture in weld metal. Also, it was essential fur the improvement of formability to perform pre- and post-welding heat treatment which cause the uniform mixture of base metal and welding consumable.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.121-123
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• 2006

The aim of present study is to investigate the effect of welding parameters and heat treatment conditions on the formability of the laser welded silicon steel sheet. It was found that there is optimum range of the heat input ($0.6{\sim}0.7kJ/cm$) and gap distance ($0.125{\sim}0.150mm$) for the high tensile strength and the avoidance of the fracture in weld metal, Also, it was essential for the improvement of formability to perform pre- and post-welding heat treatment which cause the uniform mixture of base metal and welding consumable.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.679-682
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• 2002

Resistance spot welding using air gun has been used for joining the sheet metal in automotive manufacturing process. Although air gun has many advantages, it also has the limitation to control the pressure as a factor to improve weld quality. In this study, we apply servo gun using servo motor to resistance spot welding and find the relationship between welding pressure and welding quality. Trough the experiment to change welding pressure during the welding cycle, we can make it clear that the change of welding pressure is greatly influence on the welding quality. To get in a. using response surface methodology, drew out the optimal welding pressure profile for welding quality progresses. We made an optimal profile of welding pressure which improves welding quality using response surface methodology.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.53-56
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• 2007

Magnesium sheet used in electrical device due to mobility and EMF shielding characteristics. Magnesium case by press forming was advantageous compare with conventional die casting process, because of its thin gauge of wall and surface quality. But it need to makes the boss to fix inner part or assemble the case. CD stud welding was effective way for joining the boss to the thin gauge case of the electrical devices. In this study, we investigated the performances of the magnesium boss welder To measure the process parameters such as the force and the weld current, we design the monitoring system for CD stud welding. We test the characteristics of CD stud welding for AZ31 sheets at some variables. Finally we select the optimum welding range of magnesium sheets in CD stud welding process.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.141-147
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• 2008

Hot-dip galvannealed sheet (GA) with high strength of 590MPa grade in tensile strength, has developed for automotive applications. However, for a successful application, the microstructure and galvannealing behavior of galvannealed TRIP steel sheets must be strictly controlled. High silicon contents steel has problems with weld-ability, zinc coating and reduction of retained austenite volume fraction after galvannealing process. The main purpose of this study is to solve the problem as indicated above.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.73-79
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• 2009

In order to investigate the formability of friction stir welded(FSW) tailor welded blanks(TWB) with respect to the base material's directional combination, aluminum alloy AA6111-T4 sheets were welded with three different conjoining types: RD-RD, TD-RD and TD-TD. Here, RD and TD represent rolling and transverse directions, respectively. For experimental formability study, three tests with gradual complexity were performed: the simple tension test with various weld line directions for uni-axial elongation, the hemisphere dome stretching test for biaxial stretching and the cylindrical cup deep drawing test. As a result, all three forming tests showed that RD-RD type samples exhibited the best formability, while TD-TD type sheets showed the least formability performance.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.63-65
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• 2005

Because of simple principal and low cost, resistance spot welding has been used a lot for joining the sheet metal in automotive manufacturing process. Welding current, welding time, and force are the most important variables in resistance spot wording. Air guns have hem still used widely. The requirement of synchronizing between robot and weld-gun has become bigger as the field has been automated. The number of servo-gun in the field is trending upward because there're advantages as like to synchronize with robot and to control the stroke path and force by programming on servo-gun system. But no cleared force control method is suggested on servo-gun system until now. In this study, we proved the feedback current of the servo-motor can be used to an excellent force measuring sensor and the force is controlled by the feedback current. And we also detected force lowering during welding cycle on the servo-gun system and solved by compensated force control.

• Journal of Welding and Joining
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• v.29 no.2
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• pp.40-45
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• 2011

The purpose of this study is to establish the optimum line heating condition to straighten the excessive bending distortion of a thin plate welded structure. For it, the extensive FEA and experiments were performed to evaluate the effect of heat source, heating speed and position on the straightening of a thin plate welded structure. In accordance with the results obtained by FEA and experiments, the straightening effect of line heating was strongly depends on the variables used in this study. With the results, the optimum line heating condition was established by using the response surface method and verified through comparing it with the numerical analysis result.