• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.84-89
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• 2007

This research was done on the basis of assumption that there is a relationship between welding parameters and geometry of the back-bead being a gap in arc welding. Multiple regression analysis was used as method for predicting the geometry of the back-bead. The analysis data and the verification data were used for the formation of multiple regression analysis. The method was used to perform the prediction of the back-bead.

• Proceedings of the KWS Conference
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• 1995.10a
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• pp.79-83
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• 1995

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.35-35
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• 2008

• Journal of Welding and Joining
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• v.27 no.1
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• pp.71-78
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• 2009

In the circumferential welding of pipe, welding phenomenon changes with the position of pipe. Especially in the overhead position, back bead of vertical-up position would be sunk. To investigate the size of back bead and keyhole with the change of the flow rate of pilot and shield gas at each position, bead-on plate welds were conducted on 6mm thickness SS400 with inclined-up position. When the rest of welding conditions remained constant, the width of back bead was increased as the flow rate of pilot gas was increased. And back bead tended to convex as the flow rate of shield gas was increased.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.134-135
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• 2004

해양구조물의 설치 환경 및 제품의 사용환경이 악화됨에 따라서 높은 내식성을 보이는 수퍼 이상 스테인리스강(이하: SDSS)의 사용이 많아지고 있다. 해양 구조물에 사용되는 SDSS는 대부분이 파이프자재로서 내부에서의 접근이 불가능하여 용접은 GTAW로 초층을 용접하여 이면 비드를 형성시키는 One side 용접법이 채택되고 있다. (중략)

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.17-19
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• 2007

The fatigue experiments of friction stir welded Al-6061-T6 alloy with and with out back bead were performed to investigate the variation in fatigue strength and life of the Joint. It was found that there were always existed flaws at the roots of friction stir welds for the normal welding parameters and clamping conditions. In order to overcome this root flaws, friction stir welds with optimum back bead has been developed. The test results with root flaws and with back bead were compared. The fatigue life of weld with root flaws was 5-10 times shorter than that of the friction stir weld with back bead.

• Journal of Welding and Joining
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• v.29 no.6
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• pp.77-81
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• 2011

In most industry, manual GTAW welding is preferred for formation of stable back bead in root weld of butt joint. However, manual GTAW welding has low productivity as compared with GMAW, also it has unstable bead quality which depend on skilled workers. So it is necessary to develop process of root pass welding by using automation GMAW that have stable back bead formation and high productivity. In this paper, the design of U-groove with 3mm root face was applied to extend the tolerance of misalignment in condition of standard root gap 1.5mm. Consequently, for the formation of stable back bead in root pass of butt welding, in case of the narrow root gap(0.5mm) the large arc force was applied by increasing the current and voltage. In case of the large root gap(2.5mm), the small arc force was applied by decreasing the current and voltage. Considering the various root gap, the required deposited metal was controlled by welding speed only.

• Journal of Welding and Joining
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• v.28 no.5
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• pp.86-92
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• 2010

In GMAW processes, bead geometry is a criterion to estimate welding quality. Bead geometry is affected by welding current, arc voltage, welding speed, shielding gas and so on. Thus the welding condition has to be selected carefully. In this paper, an experimental method for the selection of optimal welding condition was proposed in the root pass welding which was done along the GMA V-grooved butt weld joint. This method uses the response surface analysis in which the width and height of back bead were chosen as the quality variables of the weld. The overall desirability function, which is the combined desirability function for the two quality variables, was used as the objective function for getting the optimal welding condition. Through the experiments, the target values of the back bead width and the height were chosen as 4mm and 1mm respectively for the V-grooved butt weld joint. From a series of welding test, it was revealed that a uniform weld bead can be obtained by adopting the optimal welding condition which was determined according to the method proposed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.1
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• pp.60-68
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• 2007

It has been conducted by laser vision sensor for weldability estimation of front-bead after doing high speed butt laser welding of any condition. It has been developed a real time GUI(Graphic User Interface) system for weldability application in the basis of texts and field qualify levels. In the reference of bead imperfections, defects absolute position and defects intensity index of front-bead in the basis of formability reference, it has been produced a weldability estimation and defects intensity index of back-bead by back propagation neural network. In the result of by comparing measuring data by laser vision sensor of back-bead and data by back propagation neural network of one, it has been shown the similar results. Finally, under knowledge of welding condition in production line, it has been conducted a weldability estimation of back-bead only in knowledge of informations of front-bead data without using laser vision sensor or welding inspection experts and furthermore it can be used data for final inspection results of back-bead.

• Journal of Korean Society of Steel Construction
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• v.16 no.4 s.71
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• pp.479-492
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• 2004

When U-ribs of steel deck plates are connected at the field, overhead welding should be done with backing strips. Misalignments may occur and lead to eccentric moments as well as high stress concentrations at welded joints. In this study, stress analyses and fatigue tests were carried out. Stress analyses for U-ribs' welded joints with backing strips were performed with different misalignments, root shapes, root gaps, and backing strip sizes. From the stress analyses, the stress concentration factors increased with increasing misalignments and root gaps. With the fixed misalignments and root gaps, the stress concentration factors obtained in the case of the semi-circle root shape were lower than those in the case of the right-angle root shape. It was verified that backing strip sizes have little influence on stress concentration factors. The fatigue tests for U-ribs' welded joints with backing strips indicated that increased misalignments shorten fatigue life drastically and cracks usually initiate at the root of the base metal and are propagated to the weld bead surface. Based on the results of the stress analyses, root-shape control methods were developed to mitigate stress concentration by changing welding condition control, radius curvature, and flank angle.