• Proceedings of the KWS Conference
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• 2002.10a
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• pp.816-825
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• 2002

During the manufacture of a ship, longitudinal deformation is produced by fillet welding on the BuiltUp beam used to improve the longitudinal strength of a ship. This deformation needs a correcting process separate from a manufacture process and decreases productivity and quality. This deformation is caused by welding moment, which is the value multiplied the shrinking force due to welding by the distance from the neutral axis on a cross section of Built-Up beam. This deformation can be offset by generating a moment which is the same magnitude with and is located in an opposite direction to the welding moment on web plate by induction heating. Accordingly, this study clarifies the creation mechanism of the longitudinal deformation on Built-Up beam with FEM analysis and presents the preventative method of this deformation by induction heating basing the mechanism and verifies its validity through analysis and experiments. The induction heating used here is performed by deciding its location and quantity with experiments and simple equations and by applying them to areal structure.

• Bulletin of the Society of Naval Architects of Korea
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• v.12 no.2
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• pp.35-42
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• 1975

This paper investigates the distribution of stress and its behavior at the Root Toe in fillet welding joint. Furthermore, the stress components and principal stresses in the fillet welds are calculated by the finite element method. The distribution of stresses obtained numerically by means of the finite element method is also compared with the experimental results of two dimensional photoelasticity. A Cover plate type and Center block type of fillet welds are used as models for the numerical calculations covering the variations of 2 W/M(thickness of main plate/thickness of cover plate)=1 through 2W/M=4. The results obtained in these studies are summarized as follows; 1) When W2/M values become small, the stress concentration factors of the Root are larger than of the Toe in a C-type. Its critical value is 2W/M=3.00. However, no critical value exists in a T-type. 2) For 2W/M Values being avove 3.5 in a C-type and above 4.0 in a T-type, $K_R$ and $K_{\tau}$ become 1. 3) According to the differences of 2W/M values, the differences in stress become increasing in the Root but become decreasing in the Toe. These differences, however, disappear as the free boundary surface is approached. 4) The stress concentration factors of both the Root and Toe obtained by means of the finite element method have somewhat lower values than obtained by the photoelasiticity. But their principal stress directions coincide in either method. 5) It proves beneficial to employ the finite element method for two-dimensional plane stress analysis in front fillet welding joint.

• 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.28 no.3
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• pp.86-91
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• 2010

Stainless steel sheets are widely used as the structural material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. For fatigue design of gas welded joints such as fillet and plug type joint, it is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of gas welded joints. And also, the influence of the geometrical parameters of gas welded joints on stress distribution and fatigue strength must be evaluated. the ${\Delta}P-N_f$ curves were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curves were rearranged in the ${\Delta}{\sigma}-N_f$ relation with the maximum stress at the edge of fillet welded joint.

• Journal of Welding and Joining
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• v.18 no.2
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• pp.196-196
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• 2000

Formation of the weld defect, such as a blowhole and a pit in lap-jointed fillet arc welds has been a serious problem in arc welding of Zn-coated steel sheet. In this study, the relationship among welding conditions, welding materials and defect formation was investigated in order to minimize these defects in the CO₂ welds. In addition, the arc stability of the commercial welding wires was evaluated for revealing their effects on defect formation. Main conclusions obtained are as follows:1) There was no difference between shear tensile strength of the sound welds and that of the welds with blowholes whose diameters are less than 0.5mm. However, the welds with blowholes whose diameters are equal or larger than 0.5mm and pits exhibited tensile strength 10~20% and 30~40% lower than that of the sound welds respectively.2) The optimum welding condition to effectively prevent or reduce the weld defects formation are as follows:- The welding variables of 220A-23V-100cm/min and 120A-190V-30cm/min were recommended for minimizing the weld defects.- The gap between the two sheets at the lap-joint should be controlled to more than 0.2mm- Solid wire was less susceptible to the formation of the weld defects than the flux-cored wire.- The low welding current condition produced less weld defects than the hihg welding current condition.3) One of the reason why the amount of the defect was reduced at the low welding current was the gas discharging by the active agitation of the molten pool, due to an increasing in the number of the short circuit. (Received September 27, 1999)

• Journal of Welding and Joining
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• v.18 no.2
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• pp.69-76
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• 2000

Formation of the weld defect, such as a blowhole and a pit in lap-jointed fillet arc welds has been a serious problem in arc welding Zn-coated steel sheet. In this study, the relationship among welding conditions, welding materials and defect formation was investigated in order to minimize these defects in the CO₂welds. In addition, the arc stability of the commercial welding wires was evaluated for revealing their effects on defect formation. Main conclusions obtained are as follows: 1) There was no difference between shear tensile strength of the sound welds and that of the welds with blowholes whose diameters are less than 0.5mm. However, the welds with blowholes whose diameters are equal or large than 0.5mm and pits exhibited tensile strength 10∼ 20% and 30∼40% lower than that of the sound welds respectively. 2) The optimum welding condition to effectively prevent or reduce the weld defects formation are as follows: -The welding variables of 220A-23V-100cm/min and 120A-19V-30cm/min were recommended for minimizing the weld defects. -The gap between the two sheets at the lap-joint should be controlled to more than 0.2mm. -Solid wire was less susceptible to the formation of the weld defects than the flux-cored wire. -The low welding current condition produced less weld defects than the high welding current condition. 3) One of the reason why the amount of the defect was reduced at the low welding current was the gas discharging by the active agitation of the molten pool, due to an increasing in the number of the short circuit.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.19-25
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• 2013

The joining methods of steel structures of gas facilities, bridges, ships etc. by welding are composed mostly of T-type or cruciform fillet welding and full penetration or partial penetration according to the uses and the shape of the structures. In this study, it was examined the characteristics of fatigue crack according to penetration depth in relation to material thickness in the cruciform fillet welded joints. From the results, it was investigated the safe design stresses within the range of infinite life. When the LOP length is long the range of infinite life is small with root failure and when the LOP length is short the range of infinite life is large with teo failure. For the specimen of material thickness, 20mm welded by 3 pass compared with 10mm, 15mm welded by 2 pass, the fatigue strength and the range of infinite life was more improved by increasing of notch toughness from formation of micro-ferrite acicular structure.

• Journal of Welding and Joining
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• v.31 no.2
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• pp.63-68
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• 2013

Magnesium alloys have gained increased attention in recent years as the structural materials, because of their attractive properties such as good specific strength, excellent sound damping capability. However, to expand their applications, a reliable joining process is absolutely necessary. In this study, a CW fiber laser was used to investigate the lap weldability of sand casting and wrought magnesium alloys. The effect of defocused distance on lap weldability was examined, and it was found that spatters always generated at the around focused distance because of the high power density of the laser beam. Thus, defocused distance was required to obtain sound welds. In addition, the application of fillet welding was evaluated for minimizing the affect of sand casting magnesium alloy that have relatively poor weldability. As a result of this study, we could confirm good weldability without weld defects.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.320-323
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• 2002

This paper presents a new generation of system for pressure vessel and shipbuilding. Typical pressure vessel and ship building weld joint preparations are either traditional V, butt, fillet grooves or have narrow or semi narrow gap profiles. The fillet and U groove are prevalently used in heavy industries and shipbuilding to melt and join the parts. 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 processes such as SAW(Submerged Arc Welding) and FCAW(Flux Cored Arc Welding) can be many hours. Although SAW and FCAW are normally a mechanized process, pressure vessel and ship structures welding up to now have usually been controlled by a full time operator. The operator has typically been responsible for positioning each individual weld run, for setting weld process parameters, for maintaining flux and wire levels, for removing slag and so on. The aim of the system is to develop a high speed welding system with multitorch 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. To achieve this, a laser vision sensor, a rotating torch and an image processing algorithm have been made. Also, the multitorch welding system can be applicable for the fine grained steel because of the high welding speed and lower heat input compare to a conventional welding process.

• Proceedings of the KWS Conference
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• 1998.10a
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• pp.274-277
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• 1998