• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.315-325
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• 2017

The design dimension may not be satisfactory at the final stage due to the welding during the assembly stage, leading to cutting or adding the components in large structure constructions. The productivity is depend on accuracy of the welding quality especially at assembly stage. Therefore, it is of utmost importance to decide the component dimension during each assembly stage considering the above situations during the designing stage by exactly predicting welding deformation before the welding is done. Further, if the system that predicts whether welding deformation is equipped, it is possible to take measures to reduce deformation through FE analysis, helping in saving time for correcting work by arresting the parts which are prone to having welding deformation. For the FE analysis to predict the deformation of a large steel structure, calculation time, modeling, constraints in each assembly stage and critical welding length have to be considered. In case of fillet welding deformation, around 300 mm is sufficient as a critical welding length of the specimen as proposed by the existing researches. However, the critical length in case of butt welding is around 1000 mm, which is far longer than that suggested in the existing researches. For the external constraint, which occurs as the geometry of structure is changed according to the assembly stage, constraint factor is drawn from the elastic FE analysis and test results, and the magnitude of equivalent force according to constraint is decided. The comparison study for the elastic FE analysis result and measurement for the large steel structure based on the above results reveals that the analysis results are in the range of 80-118% against measurement values, both matching each other well. Further, the deformation of fillet welding in the main plate among the total block occupies 66-89%, making welding deformation in the main plate far larger than the welding deformation in the longitudinal and transverse girders.

• Journal of Welding and Joining
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• v.5 no.3
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• pp.19-27
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• 1987

This paper presents the weldability for cold pressure but welding method in junction of dissimilar metals each other. Although the weldability between the same aluminium metal plate welding has been studied, the study of itthe rod of aluminium and coper has not fully been investigated. The purpose is to suggest the optimal conditions on the rod of those under above method. To obtain the optimal conditions, associated experiments were performed in a various welding parameters. Consequently, it was proved that the mechanical properties such as tensile strength, hardness and bending strength could be obtained excellent particularly under the welding conditions; pressure is $(32~39) {\times} 10^3/kg/cm^2$, time is beyond 70 seconds, stage is higher than fifth stage.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.113-119
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• 2002

To prevent problems caused by welding deformation, preparation in the design stage is necessary. Countermeasures in the design stage is also the most cost-effective method. In this study, to give designers information on the welding deformation, a system to visualize the welding deformation is developed. The model to visualize the deformation is the stiffened plate common in steel structures. To increase computational efficiency, theoretical solutions to calculate the deformation of plate and stiffener are used instead of numerical analysis. Also, to secure accuracy, experiments to estimate bending moment causing welding deformations are performed. A computer program written with Visual C++ is developed for interactive data input, calculation of welding deformation and display of deformed shape. Designers can change the design in the early stage after checking the deformed shape by this system.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.1
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• pp.57-62
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• 2017

These days, shipbuilding companies are making an effort to adopt the IT technology in order to improve the production efficiency. One such effort is to utilize a planning and scheduling system to predict the production cost in advance. In this system, assessing the welding material quantity is an important factor. Unfortunately, obtaining the welding material quantity in the early design stage is extremely difficult because the detailed production information, which is essential in deriving the cost associated with welding, is normally available at a later stage. This paper aims at developing a computerized program that produces an index to estimate the welding material quantity in the early design stage. By using only three-dimensional geometric information, the program analyzes the production process and estimates the welding material quantity at any design or production stage when no production information is available. The results can be used for the planning and scheduling system.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.46.6-46
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• 2001

A servo gun welding system having a AC servo motor and a PC control system is presented for the improvement of quality control in the spot welding. The spot welding process is composed of the press stage, the weld stage, and the hold stage. The changes of gun press forces according to three stages in the spot welding process are controlled and measured through the load cell in order to know the influence on the welding quality. The relation between the measured force changes according to three stages and welding qualities is also implemented on the multilayer perceptrons, one of supervised learning method of neural network, which are powerful for realization of complex mapping characteristics. The estimated results and ...

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.2
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• pp.219-226
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• 2017

These days, the great part of design processes in the field of ship or offshore manufacturing are planned and implemented using the CAD system customized for shipbuilding companies. It means that all information for design and production could be extracted and reused at the other useful fields which need cost considerable time and efforts. The typical example is the field of welding material quantity evaluation which is demanded during the construction of ship or offshore structures. The proper evaluation of welding material to be used and the usage of them at the stage of schedule planning are mostly important to achieve the seamless process of production and costing in advance. This study is related to the calculation of welding length and needed welding material quantity at the stage of design completion utilizing the customized CAD system. The calculated welding material quantity would be classified according to welding posture, assembly stage, block, bevel and welding type so as to improve the accuracy of total cost evaluation. Moreover it is possible to predict the working time for welding operation and could be used efficiently for the cost management using the results of this research.

• Journal of Welding and Joining
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• v.24 no.5
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• pp.62-66
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• 2006

Panel line is an important process occupying the largest work amount in shipbuilding. In this research product simulation has been carried out to establish the optimal production scheduling. For this purpose a web-based panel line simulator was developed using an object modeling technology and C# language. The balance of work-load and increase in the productivity by the improvement of production facilities and process are the key factors for a good scheduling. In this study SPRT(Shortest Remaining Process Time) rule was applied for the work-load balancing and a good result achieved. To increase the productivity in the stiffener welding stage which is a bottleneck; process, more welding heads and higher welding speed were tested using the developed simulator. The simulation results showed that either more welding head or higher welding speed decreased the total work time. Use of both, however, deteriorated the productivity because of the bottleneck in the following stage. This result points out that the improvement of production facilities and/or process should be evaluated with their influences on the leading and following processing stage.

• 대한공업교육학회지
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• v.33 no.1
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• pp.282-296
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• 2008

Present automobile robot welding use $CO_2$ inert gas as a shielding fluid. The inert gas is spreading out and consumable. This present welding mechanism interfered with the welding nozzle. After welding several places have welding defects. Therefore, to reduce the $CO_2$ inert gas and to avoid interference with the material and to increase production modified nozzle which composed of cap and tip are needed. Suggested modified nozzle assembly composed of two stages i.e. $1^{st}$ and $2^{nd}$ stage. At the second stage it has 8 holes which is 3mm of diameter around the circumference. On the base of experimental results the inert $CO_2$ gas discharge reduced to 47% and welding defects decreased also. Modified two stage welding cap can be applied to the present robot welding machine and save the prime cost.

• 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.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.418-424
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• 2002

Korean Fusion Reactor(KSTAR) system consists of a vacuum vessel, in-vessel components, cryostat, thermal shield, super-conducting magnets and magnet supporting structures. These systems are in the final stage of engineering design with the involvement of industrial manufacturers. The overall configuration and the detailed dimensions of the KSTAR structure have been determined and the first stage of manufacturing is progressing now. In this study, the fabrication and assembly sequence were evaluated in viewpoint of high strengthening joints and very high accuracy. Especially for this purpose, the special cleaning process and welding process were proposed for high strengthening austenitic stainless steel which shall be used at cryogenic temperature. The draft procedure qualification data for welding process are presented with precise welding data including special narrow groove design. For the cooling line attachment on the surface of inside wall of magnet structure case, Induction brazing technology is introduced with some special jigging system and some consumables.