• Journal of Welding and Joining
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• v.20 no.4
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• pp.510-516
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• 2002

Recently the laser welding technology has been applied increasingly for the automotive bodies. But the lap joint laser welding for 3 dimensional automotive body is new while the butt joint laser welding is well known as the tailored blank technology. In this study, the process window was found for the full penetration welding of the lap joint of the 1mm-thick high strength steel sheets. The limit curves and characteristic curves were suggested to define the boundaries and the contour lines in a space of the welding speed and the gap size. The characteristics of the weld sectional geometry were used to determine the limit curves. They are bead width, penetration depth and sectional area. After the observed data was analysed carefully, it was noticed that there was a transition point at which the sectional shape was changed and the bead area jumped as the welding speed was increased. Also a new concept of 'input energy Per volume' was suggested to distinguish the difference at the transition Point. The difference of sectional areas at the transition point can be related to the dynamic keyhole phenomena.

• Bulletin of the Society of Naval Architects of Korea
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• v.14 no.3
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• pp.5-12
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• 1977

In shipyard production processes, lots of steel plates are assembled by welding. Some rectangular steel plates are buttwelded to build a large block in panel production lines. There are some advantages to take the tandem arc welding in butt joints of rectangular plates with respect to welding speed. Hence, the thermal stresses and the temperature distribution of the tandem arc welding are studied in this paper. The solutions in the case of the infinite plate with two instantaneous point heat sources have been obtained. And then the solutions have been extended to the case of two moving heat sources corresponding to the tandem arc welding with the aid of Duhamel's superposition integral. It was found that the temperature distribution was good agreement with the results of the experiments by Rosenthal and Park and the thermal stresses calculated were acceptable with respect to a physical phenomenon. These solutions are able to be applied to the problem such as a line heating.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.180.6-180
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• 2001

Welding/soldering automation is one of the most important manufacturing issues in order to lower the cost, increase the quality, and avoid labor problems. An off-line programming, OLP, is one of the powerful methods to solve this kind of diver sity problem, Unless an OLP system is ready for the path optimization in welding/soldering, a waste of time and cost is unavoidable due to an inefficient path in welding/soldering processes. Therefore, this study attempts to obtain path optimization using a genetic algorithm based on artificial intelligences. The problem of the welding path optimization is defined as conventional TSP (traveling salesman problem), but still paths have to go through welding lines. An improved genetic algorithm was suggested and the problem was formulated as a TSP problem considering ...

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.261-272
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• 2001

• Journal of Welding and Joining
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• v.25 no.2
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• pp.49-54
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• 2007

Since the wall thickness can be up to 6" or greater, welds must be made in many layers, each layer containing several passes. However, the welding time for the conventional welding processes such as SAW(Submerged Arc Welding) and FCAW(Flux Cored Arc Welding) can be required many hours. The aim of this paper is to develop a high speed welding system with multi-torch and laser vision sensor for increasing the production speed on the line and to remove the need for the operator so that the system can run automatically for the complete multi-torch multi-layer weld. It was shown that the developed laser vision sensor and analysis of arc blow for multi-torch were effective for multi-pass seam tracking and stable arc. A new automated multi-torch welding systems for thick wall applications has been proved in several production lines.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.307-313
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• 2012

This paper proposes a hand-eye laser range finder (LRF) based welding plane recognition method for autonomous robotic welding. The robot welding is the process of joining a metal piece and the welding plane along the welding path predefined by the shape of the metal piece. Thus, for successful robotic welding, the position and direction of the welding plane should be exactly detected. If the detected position and direction of the plane is not accurate, the autonomous robotic welding should fail. For precise recognition of the welding plane, a line on the plane is detected by the LRF. For obtaining the line on the plane, the Hough transform is applied to the obtained data from the LRF. Since the Hough transform is based on the voting method, the sensor noise can be reduced. Two lines on the plane are obtained before and after rotation of the robot joint, and then the direction of the plane is calculated by the cross product of two direction vectors of two lines. For verifying the feasibility of the proposed method, the simulation with the robot simulator, RoboticsLab developed by Simlab Co. Ltd., is carried out.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.612-619
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• 2002

The dynamic behavior of Al-Mg alloys plasma was very unstable and this instability was closely related to the unstable motion of keyhole during laser irradiation. The keyhole fluctuated both in size and shape and its fluctuation period was about 440 ${\mu}{\textrm}{m}$. This instability has been estimated to be caused by the evaporation phenomena of metals with different boiling point and latent heats of vaporization. Therefore, the authors have conducted the spectroscopic diagnostics of plasma induced in the pulsed YAG laser welding of Al-Mg alloys in air and argon atmospheres. In the air environment, the identified spectra were atomic lines of Al, Mg, Cr, Mn, Cu, Fe and Zn, and singly ionized Mg line, as well as strong molecular spectrum of AlO, MgO and AIH. It was confirmed that the resonant lines of Al and Mg were strongly self-absorbed, in particular in the vicinity of pool surface. The self-absorption of atomic Mg line was more eminent in alloys containing higher Mg. These facts showed that the laser-induced plasma was relatively a low temperature and high density metallic vapor. The intensities of molecular spectra of AlO and MgO were different each other depending on the power density of laser beam. Under the low power density irradiation condition, the MgO band spectra were predominant in intensity, while the AlO spectra became much stronger in higher power density. In argon atmosphere the band spectra of MgO and AlO completely vanished, but AlH molecular spectra was detected clearly. The hydrogen source was presumably the hydrogen solved in the base Metal, absorbed water on the surface oxide layer or H$_2$ and $H_2O$ in the shielding gas. The temporal change in spectral line intensities was quite similar to the fluctuation of keyhole. The time average plasma temperature at 1 mm high above the surface of A5083 alloy was determined by the Boltzmann plot method of atomic Cr lines of different excitation energy. The obtained electron temperature was 3, 280$\pm$150 K which was about 500 K higher than the boiling point of pure aluminum. The electron number density was determined by measuring the relative intensities of the spectra1lines of atomic and singly ionized Magnesium, and the obtained value was 1.85 x 1019 1/㎥.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.78-81
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• 2000

In this study the plasic flow before welding stage in the cahamber is analyzed by FEM and experiments during the porthole extrusion process. The analysis is concerned with plastic flow in the port and welding chamber of rectangular hollow section extrusion through the porthole die with mandrell. Numerical simulation by finite element code to investigate the plastic flow is discussed for both tapered inlet and straight inlet chamber. To visualize the flow in extrusion process split dies and punches are designed and manufactred by wire EDM. Experiments are carried out by using the plasticine as a model material at room temperature. The theoretical predictions are reasonable agreements with experimental results in the welding lines and the deformed profiles.

• Bulletin of the Society of Naval Architects of Korea
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• v.10 no.2
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• pp.3-8
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• 1973

In a recent year, welding is known as a most powerful process in production of pipe. For the conventional purpose, pipe is welded in axial direction to minimize the welding cost. And for the high pressure pipe, welding is done in helical direction to increase a allowable hoop stress. An analytical welding temperature distributions in a metal tube are obtained as a two dimensional case in quasi-stationary state. Numerical values which have been obtained by the analytical investigation shows a good agreement with the isocromatic lines which have been appeared at oxidized zone along the welds. Therefore it is thought that the analytical result can be used in estimating the heat effect upon the material such as a residual stress and strain, metallurgical change and etc..

• Journal of Korean Institute of Industrial Engineers
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• v.18 no.2
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• pp.83-97
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• 1992

A new approach, to seam tracking for robotic are welding is proposed. In this approach, the weld model is a snapshot image and the acquired image is analyzed and compared to the welding database which contains CAD data, weld positions, weld parameters, etc. This paper presents a fast and robust algorithm for the Hough Transform. This modified Hough Transform(MHT) algorithm uses the least-squares regression analysis method in order to approximate the edge lines more precisely, and leads to a significant reduction in both computation and storage. In comparison with the conventional seam tracking methods, this new approach has the advantages of low cost, continuous welding, and various type welding.