• Proceedings of the KWS Conference
• /
• 2001.05a
• /
• pp.186-188
• /
• 2001

• Proceedings of the Korean Society of Laser Processing Conference
• /
• 2004.10a
• /
• pp.35-39
• /
• 2004

• Proceedings of the KWS Conference
• /
• 2007.11a
• /
• pp.363-365
• /
• 2007

Titanium and its alloys have excellent corrosion resistance, high strength to weight ratios and high temperature creep properties, which make them using many various fields of application. Responding to these needs, welding processes for titanium are also being used including TIG, MIG, resistance welding, plasma arc welding, diffusion welding, electron beam welding and laser welding. In this study, It is possible to get sound beads without humping bead and spatter with the decrease of peak power according to increase of pulse width and change of welding speed for heat input control at pulsed Nd:YAG laser welding of titanium plates for Lap welding.

• Journal of Ocean Engineering and Technology
• /
• v.16 no.2
• /
• pp.53-59
• /
• 2002

This paper shows the experimental results controlling the height of surface and back bead in GMAW by analyzing the unexpected gaps between base metals produced in welding and by controlling welding velocity due to the variation of the gap between base metals in thin-plate welding. The back bead behavior and burn-through in I-type butt joint $CO_2$ welding of thin mild steel are analyzed in the views of short circuit time ratio and short circuit frequency. It is shown through experimental consideration that the short circuit time ratio method is more reasonable than the short circuit frequency method in analyzing the formulation of back bead under changing the gap between base metals. Based on the these results, welding manipulator is designed so as to satisfy the bead height control in real time by measuring the short circuit time ratio. To show the effectiveness of the developed bead formulation control system, the experiment is implemented under two welding conditions such as increasing gap from 0mm to 0.8mm and gradually increasing gap from 0mm to 1.2mm. The experimental results show that the bead formulation can be controlled uniformly in spite of the variation of the gap between base metals.

• Journal of Welding and Joining
• /
• v.16 no.1
• /
• pp.77-87
• /
• 1998

This paper deals with the effect of laser welding parameters on the weld formation. Thin steels for automotive application were prepared so as to be welded with high power carbon dioxide laser system. Major process parameters were position of focus and travel speed. The effect of shielding gas was also discussed by employing the high speed photometry. Test results showed that the optimal position of focus varied in accordance with the joint configuration; bead-on-plate, butt or lap welding. It was recommended that the position of focus for the lap welding be located at slightly inner part of the material to be welded. In this case, however, it was noticeable that the weld penetration ratio, d/t$_{0}$ dropped drastically at the critical region. Results also demonstrated that both the bead width and penetration reduced as the travel speed increased. The penetration ratio showed two distinct regions; stabilized zone at the lower range of the travel spped and sudden drop zone at the higher range of travel speed. Lower limit of the penetration for acceptable weld was proved to be about 90% of the parent metal thickness based on the physical properties of the weld. Mixed gas application for both the shielding of molten metal and laser induced plasma control was recommended as far as the penetration was concerned.d.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.10 s.241
• /
• pp.1111-1118
• /
• 2005

In this study, a unified numerical investigation has been performed on the evolution of weld pool and key-hole geometry during low-power and high-power density laser welding. Unsteady phase-change heat transfer and fluid flow with the surface tension are examined. The one-dimensional vaporization model is introduced to model the overheated surface temperature and recoil pressure during high-power density laser welding. It is shown that Marangoni convection in the weld pool is dominant at low-power density laser welding, and the keyhole with thin liquid layer and the hump are visible at high-power density laser welding. It is also shown that the transition from conduction welding to penetration welding fur iron plate exists when the laser power density is about $10^6W/Cm^2$.

• Journal of Welding and Joining
• /
• v.23 no.1
• /
• pp.55-60
• /
• 2005

A three-dimensional Gaussian heat source model is modified to include the effects of the gap and thickness-difference for the laser keyhole welding. The gap of the butt joint influences the welding efficiency such that the melting area decreases linearly with the gap. When the different plate thickness is used such as the tailored blank welding, melting areas of the thick and thin plates are predicted by introducing the thickness-difference factor. The calculated results using the modified heat source show reasonably good agreements with the experimental results.

• Journal of Welding and Joining
• /
• v.10 no.2
• /
• pp.32-42
• /
• 1992

A method of optimization of process parameters in Arc Welding has been discussed in this paper. The method of investigation is based on the numerical calculation of weld bead by a finite element method and non-linear optimization technique is applied to estimated the optimization process parameters from the numerical calculation. The common package program(ANSYS 4.4A) was used to obtain the process parameters for a thin plate arc welding (TIG, CO$_{2}$). The results on some test are satisfactory and the used method of this paper is a useful guide to the optimum welding condition.

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

• International Journal of Korean Welding Society
• /
• v.5 no.1
• /
• pp.35-43
• /
• 2005

This paper deals with the optimum condition for spot heating to correct the thin buckled panel caused by welding. Heat input models for each flame torch tip (500, 800, 2000) with standoff were establish using FEA to evaluate the temperature distribution of the heated plate and verified by experiment. With the heat input models developed for each torch tip, the effect of heating variables including ramp ratio(R) and standoff on the radial shrinkage and angular distortion was identified using FEA. Based on the results, the proper conditions of spot heating with air cooling were established. The amount and distribution of the radial shrinkage by spot heating were formulated as the function of heating variables and in-plane rigidity of the plate.