• 한국기계가공학회지
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• 제15권6호
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• pp.24-34
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• 2016

To attach a fuel tank to an excavator, two sets of mounting plates on which three bosses are attached are welded onto the tank. In this study, the welding process of a fuel tank for an excavator was modeled using a finite element numerical method. The tank was modeled as a simple plate to which the mounting plate or bosses were attached by fillet welding. Thermal and thermo-elasto-plastic analyses of the welding process were carried out to predict the temperature distribution and material distortion during welding, respectively. Three different welding sequences for the tank were also modelled to compare the deformation that occurred due to each welding sequence. The results of the analysis predicted that changing the welding sequence around the mounting plate could not position the boss within the allowable dimensional range. The results also revealed the sequence in which the maximum distortion of the bosses welded onto the tank was 30% less than the maximum distortion due to the other sequences.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.700-705
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• 2002

The welding distortion of a hull structure in the shipbuilding industry is inevitable at each assembly stage. The geometric inaccuracy caused by the 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. In order to minimize the weld-induced angular distortion in thick weldments, this paper proposes the optimum groove design for various plate thicknesses as the distortion control method. The validity of this method has been substantiated by a number of numerical simulations and experiments.

• Journal of Welding and Joining
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• 제31권3호
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• pp.54-59
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• 2013

Several methodologies analyzing welding distortions of large shell structures like ship blocks have been developed and utilized in shipyards for a long times ago. In general, one of objects of thermal distortion analysis is to find welding sequence making least-deformation without any suppliance, and it can be solved easily and rapidly by EP strain-boundary method. But after assembly construction, there are usually more than 10 weldments in each process, and the number of sequence will follow the Factorial calculation. In this research, a method has been suggested to decide the best welding sequence by minimum analysis. Using this method, welding deformation could be reduced just analyzing some cases as many as the number of weldments. Experiments and Analysis of all cases were also done, and their best results are good agreements with predictation by suggested methodology.

• Journal of Welding and Joining
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• 제6권3호
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• pp.21-26
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• 1988

The behavior of angular distortion in butt joint wleding of thin plate structure is investigated with an experimental model and partially with a computational model. The experimental model studying the effects of specimene size and degree of restraint on the angular distorion offers a good method for analyzing the behavior of the distrotion. In addition, the distrotion during welding was demonstrated by both experimental measurement and numericla prediciton. The facts evealed in this study are as follows : 1) distrotion angles were changed with variations of specimene wldth. 2) With the restraint, angular distrotion was reduced to 20% to that of free joint. 3) After the restraint being removed, the effect of restraint was also remained. 4) Same heat input per unit thickness caused same amount of distortion. 5) The mode of angular distortion was expected to be changed with expected to be changed with time, i.e. convex movement during heating and concave one during cooling.

• Journal of Welding and Joining
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• 제25권1호
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• pp.37-41
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• 2007

The purpose of this study is to establish the predictive method of angular distortion of the double-sided multi-pass butt weldment achieve it, the behavior of angular distortion in the butt weldment were investigated using comprehensive finite element analyses and experiments. The angular distortion in the multi-pass butt weldment strongly depends on the welding heat input(Q) and the effective bending rigidity of the weld throat. The effective bending rigidity of the first welding pass on the backing side was defined as the function of dimensionless parameter(k) and a bending rigidity of bead-on-plate weldment. Based on the results, the predictive equation for angular distortion of multi-pass butt weldment was proposed and verified by experiments.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.20-22
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• 2007

Welding-induced buckling distortion at the free edge of thin-plated panels has been studied. Welding distortion at free edges causes the additional man hours to straighten for the easy adjusting works of the following assembly stage. Therefore, it is necessary to develop a free-edge distortion control method. It is the purpose in the study to evaluate the effectiveness of buckling distortion prevention of the current design practice and design modification.

• 대한조선학회논문집
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• 제44권6호
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• pp.598-604
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• 2007

The purpose of this study is to establish the predictive method of welding distortion and residual stress for the channel I butt SA (submerged arc) weldment using FEA. In order to do it, the heat input model for the weldment was defined as the combined heat source with the surface heat flux of gaussian distribution and volumetric heat source uniformly distributed within weld groove by comparing the shapes of molten pool and temperature distribution obtained by FEA with those of experiments. The arc efficiency of SA welding for two-dimensional FE analysis was evaluated as 0.85. The welding distortion and residual stress of the weldment obtained by FEA and heat input model proposed have a good agreement with those obtained by experiment. Based on the results, it was suggested that the proper heat input model should be required to evaluate the welding distortion for weldment.

• Interaction and multiscale mechanics
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• 제5권2호
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• pp.145-155
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• 2012

The thin-plate structure and the box-beam structure are two typical welded structures in railway vehicles. Because of their structure complexity, bigger size and multi-seams, welding residual distortion which occur in welding process bring unfavorable effect on the quality of welding products manufacturing and service. As a result, welding distortion forecasting and control become an important and urgent research topic in railway vehicles. In this paper, three different numerical methods are presented corresponding to three typical types of welded structures of railway vehicles and welding deformation are simulated. Consistence of numerical results and experimental data proves the correctness of models and feasibility of simulation methods.

• International Journal of Korean Welding Society
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• 제5권1호
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• pp.29-34
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• 2005

Finite element analysis (FEA) and experimental studies on an elastic bending method have been performed in order to control the angular distortion at the fillet weldment for curved panel. Process parameters for the elastic bending method such as clamping span and release time were analyzed with reference to welding condition and geometric effect of the curved panel, which can minimize or prevent the angular distortion by producing a proper skin stress to the fillet weldment. The amounts of the angular distortion decrease almost in a linear manner with an increase in the skin stress. The skin stress required for non-angular distortion at the fillet weldment is strongly dependent on the plate thickness, not the heat intensity applied. The clamping span for obtaining uniform skin stress was defined as functions of the plate thickness and length of the free edge. Clamp should be removed after the fillet weldment is cooled down to room temperature for non-angular distortion. Effectiveness of the elastic bending method established was verified by its application to an actual curved panel.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.23-25
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• 2005

This paper presents a numerical analysis method for predicting welding-induced deformation and buckling in ship block with thin plates. The numerical method is particularized on evaluating buckling distortion induced by welding. There are two steps in the numerical analysis model. One is to solve the eigenvalue problem of welded structure by elastic buckling analysis, and the other is to solve the welding-induced buckling distortion of welded structure by post-mechanical analysis. Equivalent force method was used for considering the shrinkage force by welding in the analysis model.