• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.707-712
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• 2015

During the welding process, welding distortion is caused by the non-uniformity of the temperature distribution in the weldment. Welding distortion is redistributed because the residual stress and rigidity change according to the removal of the welded structure. In shipbuilding in particular, this phenomenon may be observed during the cutting process of lugs that are attached to blocks for transfer. The redistribution of welding distortion also causes problems, such as damage to the cutting tool. The aim of this study is to experimentally analyze the redistribution of welding distortion because of the partial removal of the welded structure. In the experiments conducted in this study, fillet welding and cutting were performed, and longitudinal bending and angular distortion in the welded structures were then investigated and analyzed.

• Journal of Welding and Joining
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• v.14 no.2
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• pp.36-45
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• 1996

Fatigue strength of the spot welded lap joint is considerably influenced by corrosive environments. Particularly, the chloride and the sulfide are most injurious to strength of the spot welded lap joint. Therefore, there is a need to evaluate its effect to corrosion fatigue strength for safe life design of spot welded structures. In order to evaluate their corrosion fatigue strength, corrosion fatigue tests on the spot welded lap joints of the uncoated and the coated high strength steel sheets were conducted in air and in 10% NaCl solution. Corrosion fatigue strength of the uncoated specimens were entirely lower than the coated one in NaCl solution, but those of the coated specimens in NaCl solution were lower than in air. And stress distribution in single spon welded lap joint subjected to tension-shear load was investigated by the finite element method. Using these results, we tried to evaluate corrosion fatgue strength of the various spot welded lap joints with maximum stress $\sigma_{max}$ at edge on loading side of the spot welded lap joint. We could find that corrosion fatigue strength could be quantitatively and systematically rearranged by $\sigma_{max}$.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.1
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• pp.10-18
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• 1996

This study verified the relationship between fracture mechanics parameters and X-ray parameters for normalized SS41 steel with homogeneous crystal structure and M.E.F. dual phase steel(martensite encapsulated islands of ferrite). The fatigue crack propagation test were carried out and X-ray diffraction technique was applied to fatigue fractured surface. The change in X-ray parameters(residual stress, half-value breadth) according to the depth of fatigue fractured surface were investigated. The depth of maximum plastic zone, $w_y$, were determined on the basis of the distribution of the half-value breadth for normalized SS41 steel and that of the residual stress for M.E.F. dual phase steel. $K_{max}$ could be estimated by the measurement of $w_y$.

• Journal of Welding and Joining
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• v.22 no.2
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• pp.51-58
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• 2004

Residual stresses, which can be produced during the welding process, play an important role in an industrial field. Welding residual stresses are exerting negative effect on the fatigue behavior and integrity of structure. In this study, as a result of the thermal elasto-plastic finite element analysis for the welds of a nuclear component, the residual stress distributions are estimated for as-welded condition. Also, finite element techniques are developed to simulate the relaxation of the residual stresses according to the various mechanical stress relieving(MSR) loads such as hydrostatic pressure loading, tensile pipe-end loading, and mechanical stress improvement process(MSIP) loading. Finally, the results of residual stress redistributions for various loading conditions are compared and reviewed qualitatively and quantitatively to find an optimum loading condition.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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• pp.165-169
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• 1996

In this study residual stress in weldment was considered about the effect on the fatigue propagation and about the effect of redistribution of residual stress. Then, fatigue tests were conducted by the center notched specimens machined with welded plate. The residual stress and its redistribution after the crack growth were measured by the magnetizing stress indicator and hole-drilling method. Fatigue crack propagation was estimated by the specimens having residual stress redistributed after the cracks growth and having the effects of crack closure. Crack growth rates were predicted and compared with experimental results. It had been found that the predicted crack propagation rates have a good agreement with experimental results when the redistribution of residual stress was considerd.

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.57-66
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• 2013

In this study, pullout tests were carried out to evaluate pullout characteristics of waste fishing net (WFN), which added into bottom ash for recycling both bottom ash and WFN. Three different mesh size of WFN (WFN20:$20mm{\times}20mm$, WFN30:$30mm{\times}30mm$, WFN40:$40mm{\times}40mm$) and geogrid were added as a reinforcement. Pullout characteristics of waste fishing net were compared with those of the geogrid. Pullout test results showed that pullout strength and stiffness of WFN20 are a little less than those of geogrid. However, the pullout friction angle of WFN20 is similar to that of geogrid due to bearing resistance induced from transverse rib because thickness of WFN20 is greater than geogrid. Pullout test results also indicated that distribution of residual strain along reinforcement after test depends on overburden stress. Residual strain at the tip of reinforcement increased with an increase in overburden stress due to concentration of pullout force on the tip of reinforcement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.47-54
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• 2013

This study investigates the crack growth behavior due to primary water stress corrosion cracking (PWSCC) in the dissimilar metal butt weld of a reactor piping using Alloy 82/182. First, detailed finite element stress analyses were performed to predict the stress distribution of the dissimilar metal butt weld in which the hydrostatic and the normal operating loads as well as the weld residual stresses were considered to evaluate the stress redistribution due to mechanical loadings. Based on the stress distributions along the wall thickness of the dissimilar metal butt weld, the crack growth behavior of the postulated axial and circumferential cracks were predicted, from which the crack growth diagram due to PWSCC was proposed. The present results can be applied to predict the crack growth rate in the dissimilar metal butt weld of reactor piping due to PWSCC.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.1-7
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• 2003

The objective of this paper was to investigate the welding characteristics according to the restraint condition. the pass number, and the shield gas quantity with titanium commonly using in power stations, aircrafts, ships, and so forth. The residual stress distribution was measured under restraint and nonrestraint welding conditions. The tensile strength and elongation of the 4 pass welded specimen were shown higher about 10% and 30% than those of the 7 pass welded specimen at the same welding conditions respectably. Also, the more shield gas quantity and the shorter natural cooling time, the higher tensile strength and the lower elongation.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.8-13
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• 2004

The purpose of this paper is to investigate the welding residual stress distribution according to the constraint or non-constraint welding condition with titanium commonly using power station, aircraft, and ship. The measuring method of the residual stress was applied stress release rating method with strain gages and a potable strain meter. The x direction residual stress generally showed the tensile residual stress in case of res03int welding. On the other hand, the x direction residual stress under non-restraint welding were changed tensile stress into compressive stress on 15mm away from welding bead center. Also, the y direction residual stress generally showed the tensile residual stress in case of non-restraint welding and the y direction residual stress under restraint welding were changed tensile stress into compressive stress about 60mm away from welding bead center.

• Journal of Welding and Joining
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• v.33 no.1
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• pp.72-79
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• 2015

Evaluation of fracture toughness of welded structures has a significant influence on the structural design. However the residual stresses is redistributed while the welded structures is cut for preparing specimens. This study investigated an effect of the welding residual stress redistribution on the impact absorption energy of Charpy specimen. SA516Gr70 steel plate by at the flux cored arc welding (FCAW) and gas tungsten arc welding(GTAW) was cutting. Specimens for Charpy impact testing were taken from the welded plate. Two material removal mechanisms (wire cutting and water jet) were used to make the specimens. Welding residual stress and redistribution residual stress were measured using the XRD (X-Ray Diffraction) method. The amount of redistribution of residual stress depends on the different material removal mechanism. Redistribution of residual stress of reduced the impact absorption energy by 15%.