• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.3
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• pp.254-261
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• 2020

Welding is the most convenient method for fabricating steel materials to build ships and of shore structures. However, welding using high heat processes inevitably produces welding displacements on welded structures. To mitigate these, heavy industries introduce various welding techniques such as back-step welding and skip-step welding. These techniques effect on the change of the distribution of high heat on welded structures, leading to a reduction of welding displacements. In the present study, various cases using different and newly introduced welding techniques are numerically simulated to ascertain the most efficient technique to minimize welding displacements. A numerical simulation using a finite element method based on the inherent strain, interface element and multi-point constraint function is introduced herein. Based on several simulation results, the optimal welding technique for minimizing welding displacements to build a general ship grillage structure is finally proposed.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.75-79
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• 2003

The welding distortion of a hull structure in the shipbuilding industry is inevitable at each assembly stage. This geometric inaccuracy caused by the welding distortion tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method which can explicitly account for the influence of various factors on the welding distortion. The validity of the prediction method must be also clarified through experiments. For the purpose of reducing the weld-induced bending deflection, this paper proposes the plastic counter-deforming method (PCDM) using the line heating as the optimum distortion control method. The validity of this method has been substantiated by a number of numerical simulations and actual measurements.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.20-27
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• 2016

This study deals with the proper conditions of the trail rolling method (TRM) for the prevention of the buckling welding distortion at the AA5083 GMA butt weldment. For it, the effect of the working conditions of TRM including the rolling depth and the rolling distance between the welding torch and the roller on the longitudinal welding shrinkage force of the weldment was evaluated by using 3 dimensional thermo-mechanical FE analyses. The longitudinal welding shrinkage force inducing the buckling welding distortion at the GMA butt weldment was mitigated with an increase in the rolling depth and the rolling distance between the welding torch and the roller. Based on the results, the proper conditions of trail rolling method were established to reduce the longitudinal welding shrinkage force of the GMA butt weldment to below the critical value corresponding to the bucking distortion.

• Journal of Welding and Joining
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• v.21 no.5
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• pp.561-567
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• 2003

For construction of I-beam steel structures, a fillet welding is one of the main manufacturing process. However, this welding process cause some problems associated with welding residual stress and welding deformation that are harmful to the safety of structures. Accordingly, this study clarified the creation mechanism of the welding deformation on I-beam steel structure from the experimental results given by the FEM method. To prevent or minimize the longitudinal bending deformation, first of all, a field supervision is necessary to observe the optimal groove design. Secondly, the welding order for cooling weld zone is needed.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.35-39
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• 2003

Laser welding has good characteristics such as high density energy, high speed and short heating time, as compared with conventional arc welding. The joint of laser welding also has good mechanical characteristics in general. However, relevant research is not sufficient to understand laser welding in the view point of mechanics until a recent date. In this paper, numerical simulation has been conducted to analyze distribution of welding residual stresses. Welding residual stresses of specimen have been measured by using sectioning method to compare the results between simulation and experiment.

• Journal of Welding and Joining
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• v.22 no.1
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• pp.58-64
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• 2004

The control of the weld bead shape is important in laser welding of the small parts. The effects of laser welding parameters on the weld bead shape in the pulsed Nd:YAG laser welding of STS 304L material were investigated. Shielding gas type, flow rate, pumping voltage, pulse frequency, pulse width, focal position and overlap distance were selected as laser welding parameters. Experiments were designed and conducted using the Taguchi method which was a statistical experimental method. The weld bead width, penetration, area and aspect ratio were measured and analysed as the weld bead shape properties and the welding parameters were optimized to maximize the weld aspect ratio. Weld aspect ratio were greatly affected by the pulse width, pumping voltage and pulse frequency, and somewhat by the overlap distance, and little by the shielding gas type, flow rate and focal position. A confirmation experiment were conducted using the optimized welding parameters.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.27-30
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• 2008

It was investigated that two rods of aluminium can be welded by hot extru-welding method with extru-welding dies, and that the extru-welding on the welding surface were analyzed by computer simulation according to the steped shapes of welding dies. It was known by computer simulation that welding pressure on the welding section of rods welded using extru-welding dies and that the welding pressure on the welding section of rods using extru-welding dies is lowerer than the welding pressure of rods using stepped welding dies. And it was known by experiments that two rods of aluminium can be welded on the end sections by hot extru-welding method using fan-shaped stepped welding dies without relative rotational movement of contacted aluminium rods needed for the purpose of friction heating and pressure.

• Transactions of Materials Processing
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• v.17 no.4
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• pp.284-291
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• 2008

It was investigated that two rods of aluminum can be welded by hot extru-pressure welding method with stepped welding dies, and that the welding pressure and metal flow on the welding surface were analyzed by computer simulation according to the stepped shapes of welding dies. It was known by computer simulation that welding pressure on the welding section of rods welded using stepped welding dies could be higher than the welding pressure of aluminum rods without using stepped welding die. And it was known by experiments that two rods of aluminum can be welded on the end sections by hot extru-pressure welding method using stepped welding dies without relative rotational movement of contacted aluminum rods in the case of friction welding of rods.

• Journal of Ship and Ocean Technology
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• v.8 no.3
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• pp.40-49
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• 2004

Welding deformations injure the beauty of appearance of a structure, decrease its buckling strength and prevent increase of productivity. Welding deformations of real structures are complicated and the accurate prediction of welding deformations has been a difficult problem. This study proposes a method to predict the welding deformations of large structures accurately and practically based on the simplified thermal elasto-plastic analysis method. The proposed method combines the inherent strain theory with the numerical or theoretical analysis method and the experimental results. The weld joint is assumed to be divided into 3 regions such as inherent strain region, material softening region and base metal region. Characteristic material properties are used in structural modeling and analysis for reasonable simplification. Calculated results by this method show good agreement with the experimental results. It was proven that this method gives an accurate and efficient solution for the problem of welding deformation calculation of large structures.

• Journal of Welding and Joining
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• v.10 no.2
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• pp.19-31
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• 1992

A numerical study was performed to investigate the flow field and the heat transfer characteristics occurring in high power density welding which is important in many fields of engineering applications. A two dimensional quasi-steady state of keyhole welding model is simulated by using the finite volume methods. It is shown that the shape of isothermal line is elliptic and the temperature gradient is very steep compared with other welding method and the welding speed has on welding width and observed beam power.