• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.197-200
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• 2006

The portion of thin plate is expected to increases as to the development of design and fabrication technology. The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates, and in addition internal and external constraints much more influence upon weld-induced deformation of thin plates. This paper deals with the application of the mechanical tensioning method to fillet weld of thin plates to reduce the weld-induced deformation. For this, fillet welding test have been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. From the present study, it has been found that the tenssoning method is effective on reduction of weld-induced deformation.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.6
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• pp.590-597
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• 2007

The portion of thin plate is expected to increases as to the development of design and fabrication technology. The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates, and in addition internal and external constraints much more influence upon weld-induced deformation of thin plates. This paper is aimed at applying the mechanical tensioning method to fillet weld of thin plates to reduce the weld-induced deformation. For this purpose, fillet welding tests have been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. From the present study, it has been found that the tensioning method is effective on reduction of weld-induced deformation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.298-302
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• 2011

티타늄 용접부는 수소취성과 잔류응력에 대한 영향을 최소화 하기 위해 용접 후 잔류응력 제거 열처리 작업을 수행하고 있다. 하지만, 현재 항공 분야에 널리 사용하고 있는 규격에 따라 열처리 온도가 다양하게 설정되어 있어 현장에 적용하기에는 어려움이 있다. 이에 규격 별로 대표하고 있는 열처리 조건을 선정하여 열처리 조건에 따른 용접부에 대한 잔류응력, 잔류수소량을 확인하였고, 용접부에 대한 강도와 충격 인성을 확인하였다.

• International Journal of Korean Welding Society
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• v.3 no.2
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• pp.29-39
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• 2003

The durability and reliability of thermal barrier coatings (TBCs) play an important role in the service reliability, availability and maintainability (RAM) of hot­section components in advanced turbine engines for aero and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary non­destructive evaluation (NDE) techniques for quality control and life­remain assessment of TBCs. This paper overviews the governing principles and applications of the luminescence and the impedance examined in the light of residual stress, phase constituents and resistance (or capacitance) in TBC constituents including the thermally grown oxide (TGO) scale. Results from NDE by PSLS and EIS are discussed and related to the microstructural development during high temperature thermal cycling, examined by using a variety of microscopic techniques including focused ion beam (FIB) in­situ lift­out (INLO), transmission and scanning transmission electron microscopy (TEM and STEM).

• Journal of Welding and Joining
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• v.23 no.3
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• pp.68-75
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• 2005

The fatigue life of welded joints is associated with crack initiation and propagation life. Theses cannot be easily separated, since the definition of crack initiation is vague due to the initiation of multiple cracks that are distributed randomly along the weld toes. In this paper a method involving a notch strain and fracture mechanical approach, which considers the characteristics of welded joints, e.g. welding residual stress and statistical characteristics of multiple cracks, is proposed, in an attempt to reasonably estimate these fatigue lives. The fatigue crack initiation life was evaluated statistically, e.g. the probability of failure occurrence in 2.3, 50 and $97.7\%$, in which the cyclic response of the local stress/strain hi the vicinity of the weld toes and notch factors derived by the irregular shape of the weld bead are taken into account. The fatigue crack propagation life was simulated by using Monte-Carlo method in consideration of the Ad-factor and the mechanical behavior of mutual interaction/coalescence between two adjacent cracks. The estimated total fatigue life, $(N_T)_{P50\%}$, as a sum of crack initiation and propagation life under the probability of failure occurrence in $50\%$ showed a good agreement with the experimental results. The developed technique for fatigue lift estimation enables to provide a quantitative proportion of crack initiation and propagation life in the total fatigue life due to the nominal stress range, ${\Delta}S$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.3
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• pp.19-25
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• 1984

In the welded structure, the most dengerous section is welded parts and almost fractures of welded structure occur from welded parts. Accordingly, in other to prevents of fracture, it is important seeking the fracture behavior of welded parts. In this study as basic investigation of fracture behavior of welded parts, it is investigated that local distribution of fracture toughness and effect of multipass electrode welding, also effect of release of residual stress were investigated, as the subjected. material, the used steel having fatigue history and unused steel were selected. As the result of this study, it is dear that the base metal of unused steel and heat affected zone and weld metal are different each other in fracture toughness, and it seems clear that the weld metal may will become source of fracture because of it having the most low fracture toughness. Especially, in the case of crack occur in the used steel, it will be the most brittle section in the structure because of it having low fracture toughness then weld metal. It affirmation that, if welded parts has not flaw, the multi pass electrode welding effective to improve of fracture toughness, also release of residual stress is none effective to improve of fracture toughness in this study.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.1 s.151
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• pp.32-39
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• 2007

A three-dimensional finite element model has been developed to simulate the MIG P/S welding process of two aluminum plates. The finite element calculations are performed using ANSYS finite element code, which takes into account the thermal and mechanical non-linear material properties. The results of finite element analysis compared with those of experiment to show its validity in view of distortions. Parametric studies are carried out on the validated model to assess the effects of various factors on the final residual distortion. Large deformations, temperature dependent material properties are included in the model. Finally, the formulas of fitting curves of angular distortion transverse shrinkage, and longitudinal shrinkage have been proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.125-136
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• 1984

In the weled structures, fatigue fracture mainly depends upon crack growth behavior. Specially anisotropy of crack growth orientation and welding direction become important factor of fracture in the welding jone. When fatigue stressed steel welded with nonfatigue stressed steel, at the low stress intensity factor range, residual stress become more important factor of growth behavior then properties of base metal but when the crack growth in the weld metal, toughness of weld metal become the most important factor. Especially nonhomgeniety of toughness for the weld metal make more scatter the relations of $da/dN-{\Delta}K$.

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.72-79
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• 2002

In this study, time-dependent distributions of temperature and stresses, in the box-column welded from ultra thick plates with center segregation, has been analyzed by the commercial finite element package SYSWELD+, for several types and angles of groove. The major points of investigation are the optimum type and angle of groove that minimize weld stress specially at the center segregation, as well as temperature distribution, residual stresses and changes in the mechanical properties. The results can be summarized as follows; 1) Generally the thermal cycle at the root of groove exhibits relatively rapid cooling pattern, however, most of the other part weldment have a slow cooling pattern in all groove types. 2) Most of the micro-structures of weldment are composed of ferrite and pearlite, meanwhile we could find martensite and bainite locally a the root of the groove. 3) Optimum groove type for high heat input welding of box-column corner is a double groove type, and the optimum angle for the groove is 30~$45^{\circ}$ that minimize deformation and weld stress at the center segregation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.261-269
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• 2003

Steel bridges, which have been damaged by load and corrosion, need repair or strengthening. In general, before the repair welding procedure, cutting procedure carry out. Therefore, the investigating of the behavior of stress generated by cutting is so important for safety of structure. Residual stress produced by gas cutting was analyzed using 2D and 3D thermal elasto plastic FEM. According to the results, the magnitude of temperature was analyzed by 2D FEM is smaller than that was analyzed using the 3D FEM program at the start and end edge of flange. And the magnitude and distribution of residual stress of perpendicular to the cutting line was analyzed by the 2D FEM program was similar to that was analyzed by the 3D FEM program. Therefore, it is possible to predict of cutting stress by 2D and 3D FEM.