• Proceedings of the KWS Conference
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• 2002.05a
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• pp.258-259
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• 2002

• Journal of Welding and Joining
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• v.32 no.5
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• pp.44-49
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• 2014

The effect of weldbond hybrid joining process on the mechanical behavior of single lap and L-tensile joints was investigated for the newly developed 1.2GPa grade ultra high strength TRIP(transformation induced plasticity) steel. In the case of single lap shear behavior, the weldbond joint of 1.2GPa TRIP steel showed lower maximum tensile load and elongation than that of the adhesive bonding only. It was considered to be due to the reduction of real adhesion area, which was caused by the degradation of adhesive near the spot weld, and the brittle fracture behavior of the spot weld joint. In the case of L-tensile behavior, however, the maximum tensile load of the weldbond joint of 1.2GPa TRIP steel was dramatically increased and the fracture mode was change to the base metal fracture which is desirable for the spot weld joint. These synergic effect of the weldbond hybrid joining process in 1.2GPa TRIP steel was considered to be due to the stress dissipation around the spot weld joint by the presence of adhesive which resulted in the change of crack propagation path.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.7
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• pp.667-672
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• 2016

This study presents results of an experimental investigation of the laser-arc, hybrid, butt welding process of SS400 structural steel. Welding parameters including laser power, welding current and speed were varied in order to obtain one-pass, full-penetration welds without defects. The conditions that resulted in optimal beads were identified. After welding, hardness measurements and microstructure observations were carried out in order to study weld properties. The mechanical properties of both the base material and welded specimen were compared based on the results of tensile strength measurements. The yield and tensile strengths were found to be similar.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.227-229
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• 2003

Low heat input welding methods have been investigated in order to minimize the HAZ softening of the 600MPa grade fine grained steel weldment. The welding processes of interest were a high speed FCA welding with a multi-torch welding system, laser welding with filler feeding and hybrid laser welding. No HAZ softening was found for all the weldments formed with low heat input less than 10kJ/cm. Tensile strength of the weldments was high enough to satisfy the required value. Impact toughness of the weldments was also good even at -20$^{\circ}C$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.78-81
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• 2005

The aluminum Subframe for automobile was developed using hybrid process, i.e. extruforming and press forming. To achieve a $30\%$ weight reduction compared with convensional steel subframe keeping satisfactory performance, the design of cross-section of extrusion part was initiated, then forming simulation was performed and the final design was determined. In addition, we tried to estibilish proper aluminum welding conditions for good penetration depth and few pore defact, finally the prototype of aluminum subframe was assembled using MIG welding method.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.206-208
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• 2004

Korea holds the first rank in the world for shipbuilding industry, we should develop the welding technology which is fundamental technique in order to keep the first rank. In this study, therefore, welding characteristics of shipbuilding steel using arc and laser were compered experimentally to apply laser-arc hybrid welding system in the heavy industry including shipbuilding as next generation welding process.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.240-242
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• 2005

• Journal of Welding and Joining
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• v.28 no.3
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• pp.42-48
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• 2010

Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) were welded by a combination of a diode laser and a CNC machining center. Laser beam delivered through the transparent PC and was absorbed in an opaque ABS. Polymers were melted and joined by absorbed and conducted heat. Experiments were carried out by varying working distance from 44mm to 50mm for the focus spot diameter control, laser input power from 10W to 25W, and scanning speed from 100 to 400mm/min. The weld bead and cross-section were analyzed for weld quality, and tensile results were presented through the joint force measurement. With focus distance at 48mm, laser power with 20W, and welding speed at 300mm/min, experimental results showed the best welding quality which bead size was measured to be 3.75mm. The shear strength at the given condition was $22.8N/mm^2$. Considering tensile strength of ABS is $43N/mm^2$, shear strength was sufficient to hold two materials. A single process was possible in a CNC machining system, surface processing, hole machining and welding. As a result, the process cycle time was reduced to 25%. Compared to a typical process, specimens were fabricated in a single process, with high precision.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1379-1386
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• 2005

For efficient welding it is necessary to maintain stability of the welding process and control the shape of the welding bead. The welding quality can be controlled by monitoring important parameters, such as, the Arc Voltage, Welding Current and Welding Speed during the welding process. Welding systems use either a vision sensor or an Arc sensor, both of which are unable to control these parameters directly. Therefore, it is difficult to obtain necessary bead geometry without automatically controlling the welding parameters through the sensors. In this paper we propose a novel approach using fuzzy logic and neural networks for improving welding qualify and maintaining the desired weld bead shape. Through experiments we demonstrate that the proposed system can be used for real welding processes. The results demonstrate that the system can efficiently estimate the weld bead shape and remove the welding detects.

• Journal of Welding and Joining
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• v.22 no.6
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• pp.30-35
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• 2004

Laser welding is obviously an attractive method to join small, thin parts such as small stainless steel tubes, but it is very sensitive to the joint clearance and tolerance, and this makes laser welding difficult to obtain consistent welding qualities over time. Recently, Plasma Augmented Laser Welding(PALW) is being developed to solve these problems. In this study, plasma arc welding(PAW) was introduced to join conventional V-grooved butt joint of thin stainless steel strips using single laser heat source in manufacturing small stainless steel tubes. The effect of the welding speed enhancement is investigated by the experiments. Effects of welding directions, distance between the heat sources and intensity of arc heat source on the optimal welding speed was investigated. Through this research, it was confirmed that PALW process has higher welding speed and robustness than laser welding process.