• Journal of the Society of Naval Architects of Korea
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• v.48 no.1
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• pp.56-61
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• 2011

In this study, a series of fatigue tests was conducted to evaluate fatigue strength for the root gap difference with high strength steel with butt welded joints. A finite element analysis using effective notch stress method was also performed to compare effective notch factors each other with butt welded specimens made by copper backing. The results of fatigue tests were classified according to the root gap difference. Fatigue life of butt welded specimens is presented for determining the root gap of high strength steel with butt welded joints in terms of fatigue strength. Then effective notch stress was applied to interpret fatigue strength of butt welded specimen model which is reflected actual measured dimensions. As a result, fatigue strength of high strength steel with butt welded specimens is increased by root gap gets longer in length.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.101-113
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• 1998

In this study, we research the influence of butt-welded joints in high tension bolted joints on the static and fatigue strength. As a results, if it's located inside or outside of the friction surface, the fatigue strength decrease, and the decrease of fatigue strength is greater in cases that the butt-welded joints exist outside of the friction surface. But the influence of butt-welded joint on the fatigue strength satisfies category B of the Specifications.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1058-1062
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• 1996

The assessments of weld defects by fracture mechanics are performed for design of welded Joints. In general, butt, T-type, and L-type welded joint are useful for welding structure. When linear weld defects are in welded joint, stress intensity factors for each joints are calculated by finite element method. Analysis results are shown for the fracture modes and characteristics of joint types. And they are founded for the weaken order of welded joints being T-type, butt, L-type.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.497-508
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• 1998

The objective of this study is to examine fatigue behavior of as-welded butt-welded joints with incomplete penetration from fatigue tests. The test results are the following. In static tests, tensile strength and yield strength of butt-welded joints are constant regardless of incomplete penetration. And in fatigue tests, fatigue strength of fully penetrated butt-welded joints satisfies fatigue limits, prescribed in Korean Specifications and JSSC, respectively. The results show that as the magnitude of incomplete penetration increases, fatigue strength decreases. In fractured surfaces, full and incomplete penetration specimen show different shapes, it is because that stress concentration factor vary with structural geometry in bead toe and root tip, and certify in FEM analysis. This study suggests that defects such as incomplete penetration from welding must be avoided in order to attain the sufficient life of steel structures.

• Journal of Welding and Joining
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• v.22 no.4
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• pp.59-64
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• 2004

The purpose of this study is to investigate the influence of weld bead profiles on stress concentration factors of double V groove butt-welded joints. The influence of three parameters such as toe radii, flank angles and bead heights on the stress concentration factors is studied by finite element analysis. It is shown that the three parameters have similar effects on the stress concentration factors. Finally a formula to estimate the stress concentration factors considering the three parameters and others is proposed and estimated results are compared with the results obtained by finite element analysis.

• Structural Engineering and Mechanics
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• v.60 no.1
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• pp.51-69
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• 2016

A large number of welded steel moment-resisting framed (SMRF) structures failed due to brittle fracture induced by ductile fracture at beam-to-column connections during 1994 Northridge earthquake and 1995 Kobe (Hyogoken-Nanbu) earthquake. Extensive research efforts have been devoted to clarifying the mechanism of the observed failures and corresponding countermeasures to ensure more ductile design of welded SMRF structures, while limited research on the failure analysis of the ductile cracking was conducted due to lack of computational capacity and proper theoretical models. As the first step to solve this complicated problem, this paper aims to establish a straightforward procedure to simulate ductile cracking of welded joints under monotonic tension. There are two difficulties in achieving the aim of this study, including measurement of true stress-true strain data and ductile fracture parameters of different subzones in a welded joint, such as weld deposit, heat affected zone and the boundary between the two. Butt joints are employed in this study for their simple configuration. Both experimental and numerical studies on two types of butt joints are conducted. The validity of the proposed procedure is proved by comparison between the experimental and numerical results.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.141-147
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• 2014

This study aims to investigate the influence of bevel angles on the fatigue life of V-groove butt-welded joints with back-plates made by SM490A steel material, generally used for excavators, because changes in the geometry, material and surface properties of welded regions affect the fatigue life of welded structures. Butt type test specimens were prepared by the $CO_2$ welding of rolled steel plates (SM50A steel) with a thickness of 13.5 mm at a welding speed of 30 cm/min and these Butt type test specimens had two different groove angles, which are $40^{\circ}$ (A type) and $30^{\circ}$ (B type). In order to investigate differences in fatigue life between two types, 4-point bending fatigue tests were conducted with a stress ratio of R=0.1 under the cyclic loading environment at a frequency of 5 Hz at room temperature. The fatigue life of A type specimens was approximately 7% higher than that of B type specimens. The stress concentration factors calculated by finite element analysis were 2.16 for A type and 2.25 for B type, whose difference was caused by the influence of the back-plates of butt-welded structures. The current results could provide important guidelines to determine the V-groove angle of butt-welded joints with a satisfactory fatigue life, although under severe operating conditions.

• International journal of steel structures
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• v.18 no.5
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• pp.1631-1638
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• 2018

In the periodic repainting of steel bridges, often the steel surface has to be prepared by using power tools to remove surface contaminants, such as deteriorated paint film and rust, and to increase the adhesive strengths of the paint films to be applied newly. Surface preparation by bristle roll-brush grinding, which is a type of power tool, may additionally introduce compressive residual stress and increase the fatigue resistance of welded joints owing to the impact of rotating bristle tips. In this study, fatigue tests were conducted for longitudinally out-of-plane gusset fillet welded joints and transversely butt-welded joints to evaluate the effect of bristle roll-brush grinding prior to repainting on the fatigue resistance of the welded joints. The test results showed that bristle roll-brush grinding introduced compressive residual stress and significantly increased fatigue limits by over 50%.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.339-350
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• 1999

In this study, blowholes, a kind of solid defects, were intentionally introduced in transverse butt-welded joints which are widely used for the connection of main members in steel structures to evaluate the fatigue characteristics of these joints with blowholes according to the difference of the size and shape of blowholes, and a series of tests were performed. Static test results proved that the static strength of these joints with blowholes was not affected by their size and shape. From the fatigue test results on these joints with blowholes, the size and shape of blowholes inside the weld metals were strongly affected in fatigue strength, and we suggested the relationship between fatigue strength and their size and shape quantitatively. Also, Using the relationship of fatigue crack growth rate and stress intensity factor range, the fatigue life of transverse butt-welded joints with blowholes can be estimated properly.

• Journal of Welding and Joining
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• v.21 no.1
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• pp.72-79
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• 2003

Fatigue behaviour of partially penetrated butt-welded joints in high strength steel plates, in which crack-like structural defect, i.e. lack of penetration(LOP), is inevitably introduced during welding processes, was investigated. Fatigue lives of two types of welded joints, namely X-grooved and K-grooved joints, were experimentally determined first. Observed fatigue crack propagation behaviours of the partially penetrated butt-welds were interpreted through considering 3-dimensional semi-elliptical crack shape in front of the LOP. Based on such interpretation, a fracture mechanical method to estimate stress intensity factors at the crack tip was proposed. Since the fatigue lift of the partially penetrated butt-welds was strongly influenced by the ratio of size of the LOP to thickness, D/t, the D/t was used as a main parameter to calculate the fatigue lift by using the proposed method. Comparison of the fatigue lift obtained experimentally and analytically agreed well with each other. Hence it is suggested that the method used in this work to predict fatigue lift of the partially penetrated butt-welds can be applied to real cases with improved lift-prediction capability.