• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.977-985
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• 2004

An evaluation of fatigue life of welded components is complicated due to various geometrically complex welding details and stress raisers in vicinity of weld beads, ego under cuts, overlaps and blow holes. These factors have a considerable influence on the fatigue strength of welded joints, as well as the welding residual stress which is relaxed depending on the distribution of local stress at the front of the stress raisers. To reasonably evaluate fatigue life, the effect of geometries and welding residual stress should be taken into account. The several methods based on the notch strain approach have been proposed in order to accomplish this. These methods, however, result in differences between analytical and experimental results due to discrepancies in estimated amount of relaxed welding residual stress present. In this paper, an approach that involves the use of a modified notch strain approach considering geometrical effects and a residual stress relaxation model based on experimental results was proposed. The fatigue life for five types of representative welding details, ego cruciform, cover plate, longitudinal stiffener, gusset and side attachment joint, are evaluated using this method.

• Journal of Welding and Joining
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• v.25 no.4
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• pp.20-27
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• 2007

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.175-182
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• 2003

The fatigue life of welded joints is sensitive to welding residual stress and complexity of their geometric shapes. To predict the fatigue life more reasonably. the effects of welding residual stress and its relaxation on their fatigue strengths should be considered quantitatively, which are often regarded to be equivalent to the effects of mean stresses by external loads. The hot-spot stress concept should be also adopted which can reduce the dependence of fatigue strengths for various welding details. Considering the factors mentioned above, a fatigue life prediction model using the modified Goodman's diagram was proposed. In this model, an equivalent stress was introduced which is composed of the mean stress based on the hot-spot stress concept and the relaxed welding residual stress. From the verification of the proposed model to real welding details, it is proved that this model can be applied to predict reasonably their fatigue lives.

• Journal of Welding and Joining
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• v.34 no.4
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• pp.62-66
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• 2016

The trend of the fabrication technology of high strength, high toughness aluminum alloys by the severe plastic deformation(SPD) process and the welding technology of lightweight alloys in the automobile has been studied. The lightweight aluminum alloys can reduce vehicle weight, while stringently demanding the high quality and efficient welding techniques, to produce the best weldments. Among the production technologies, welding plays an important role in the fabrication of lightweight vehicle structure. This paper covers the scientometric analysis of the severe plastic deformations of lightweight alloys and the welding technology in the automobile which are based on the published research works in the 'HPT, ECAP and rolling', and 'welding technology of the automobile' obtained from Web of Science, and deals with the details of the background data of the HPT, ECAP, and rolling of lightweight alloys, and welding technology of the automobile technology.

• Steel and Composite Structures
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• v.10 no.3
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• pp.261-279
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• 2010

Generally, a box tube, which is used for an existing square CFT structure, is made by welding four plates. The manufacturing efficiency of this steel tube is poor, and it also needs special welding technology to weld its internal diaphragm and the through diaphragm. Therefore, an interior-anchor-type square steel tube was developed using the method of cold-forming thin plates to prevent welding of the stress concentration position, and to maximize the section efficiency. And, considering of the flow of beam flange load, the efficiency of erection and the weldability of the diaphragm to thin walled steel column, the external diaphragm connection was selected as the suitable type for the welded built-up square CFT column to beam connection. And, an analytical study and tests were conducted to evaluate the structural performance of the suggested connection details and to verify the suggested equations for the connection details. Through this study, the composite effect of the internal anchor to concrete, the resistance and stress distribution of the connections before and after the existing column is welded to the beam, the effective location of welding in connection were analyzed.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.05a
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• pp.408.1-408.1
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• 2003

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.192-197
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• 2005

A welding bead height is closely related to the efficiency of welding work, and the height of 3mm is used in the conventional practice of butt welding. in the present paper, the modification of bead height from 3mm to 6mm is considered to increase the efficiency and work productivity of butt welding on bottom plate (of BONGA FPSO actually built in SHI shipyard). Therefore, fatigue analysis has been carried out using simplified method based on the DNV Rules. It is found that the minimum fatigue life is about 594 years and the butt welding details with 6mm bead height has sufficient strength and resistance against fatigue.

• International Journal of Korean Welding Society
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• v.1 no.1
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• pp.51-57
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• 2001

Effect of the joint details on the stress distribution over a slot structure has been studied in order to improve its fatigue life using a finite element analysis. The joint details of interest are the radius and height of scallop at the stiffener as well as the mis-alignment between the stiffener and longitudinal member. For a slot structure currently used, the stiffener heel is subjected to the maximum stress for a given external load, where is a potential fatigue crack initiation site. The stresses at the stiffener heel and toe decrease both by increasing the scallop radius and more significantly by increasing the mis-alignment while no notable effect of the scallop height on it is appreciated. A proper combination of these factors makes it possible to reduce the stresses at the stiffener heel and In, theoretically, more than 50%. This is attributed to the modification of the stress distribution over the slot structure including the transition of the maximum stressed region from the stiffener heel to the slot surface of the transverse web. Such then results in a g[eat improvement of the fatigue life of the slot structure.

• Journal of Ocean Engineering and Technology
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• v.24 no.4
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• pp.53-58
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• 2010

Offshore floater such as FPSO, drillship is composed of topside and hull side, and the interface structure is called topside module support. In this study, practical considerations were investigated for the design of topside module supports, from the concept design stage to the final stage of structural determination, in view of design efficiency and construction productivity. The effects of welding design factors of topside module support, such as welding throat thickness, sectional welding area, and welding man-hours, were compared and analyzed closely with respect to productivity. The current status and problems regarding the application of deep or full penetration welding are discussed, and a direct-calculation method is suggested as a possible solution to these problems.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.125-129
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• 2002

Authors had developed the model for the fatigue life assessment of welded details considering residual stress and its relaxation. The model consists of three ingredients; a hot-spot stress approach, a residual stress relaxation, and an equivalent stress. The equivalent stress is induced by stress ranges and the ratios between the applied mean stresses and the ultimate stress of material. Once being tuned with two specific fatigue tests by using load carrying cruciform joint, this model can be applied to many kinds of welded details which structural stress concentration factors are different from each other. This paper reports the application of the proposed model for various welded details including cover plate, longitudinal stiffener, gusset and side attachment. From the investigation of predicted results by using the proposed model it was shown that the ambiguous fatigue characteristics of the various details influenced widely by the welding residual stress are clarified, and also the model could be applied to assess fatigue life of general welded structures.