• 한국공작기계학회논문집
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• 제17권3호
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• pp.115-121
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• 2008

A knowloedge of the residual stress distribution at circumferential welds can increase the prediction accuracy of a fracture assessment in pipe lines. In this study, in order to predict the residual stress distribution in the circumferential butt-welded pipes were measured, using the hole-drilling strain gauge method. Their practical applications were performed in to two kinds of pipes. As the results, the following characteristics were found. On the inner surface of pipes, the circumferential and axial residual stresses were both tensile near the center line of welding and both of them changed from tensile to compressive as the distance from the center line increased. On the outer surface, however, the circumferential residual stress was shown to be tensile wile the axial residual stress was compressive near the center line of welding, and later they were revered at the region far away from the centerline.

• Journal of Welding and Joining
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• 제15권2호
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• pp.81-88
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• 1997

The residual stresses produced by a circumferential weld between axisymmetric cylinders are one of the most important problems concerning buckling strength, fatigue strength, stress corrosion cracking in shell structures, and arc quite different from those due to a butt weld between flat plates. This paper presents experimental studies on weld cylinder models of various heat inputs and thin cylinder diameters by blind hole drilling method. As a result, it is certified that weld residual stress (axial stress and hoop stress) is larger, as heat input and shell cylinder diameter are larger, and that experimental results show good agreement with the result of preceding researchers.

• Journal of Welding and Joining
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• 제15권5호
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• pp.115-123
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• 1997

The buckling strength, fatigue strength, stress corrosion cracking are considerably effected on one of initial imperfections, the residual stresses produced by a circumferential weld between axisymmetric cylinders. Therefore, we study the residual stresses, plastic strain and temperature distribution with using thermal elasto-plastic analysis which are generated by a circumferential weld between axisymmetric cylinders. It is investigated that welding residual stresses have an effect on the strength of cylinder for inner and outer shell under external pressure.

• 한국압력기기공학회 논문집
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• 제16권1호
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• pp.100-109
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• 2020

Pipelines subjected to ground movement would be easily exposed to large-scale deformation. Since such deformations may cause the pipeline failure, it is important to ensure the safety of pipelines in various operation conditions. However, crack in weld metal have been considered as one of the main causes that can deteriorate the structural integrity of the pipeline. For this reason, the structural integrity of the pipe containing the crack in the weld should be obtained. In order to assess cracked pipe, J-integral and crack-tip opening displacement(CTOD) have been applied widely as the elastic-plastic fracture mechanics parameters representing crack driving force. In this study, engineering solutions to calculate the J-integral and CTOD of pipes with a circumferential outer surface crack in the weld are proposed. For this purpose, 3-dimensional elastic-plastic finite element(FE) analyses have been performed considering the effect of overmatch and width of weld. The shape of the weld was simplified to I-groove, and axial displacement was employed as for loading condition. Based on FE results, the effects of crack size, material properties and width of weldment on J-integral and CTOD were investigated. Additionally, the J-integral and CTOD for I-groove were compared with those for V-groove to examine the effects of the weld shape, and a proportionality coefficient of J-integral and CTOD was calculated from the results of this paper.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.67-72
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• 2008

The objective of this study is to design a laboratory specimen for simulating residual stress of circumferential butt welding of pipe. Specimen type and method for residual stress generation were proposed based on the review of prior studies and parametric finite element simulation. To prove the proposed specimen type and loading method, the residual stress was generated using the designed specimen by applying proposed method and was measured. The measured residual stress using X-ray diffraction reasonably agreed with the results of finite element simulation considered in the specimen design. Comparison of residual strains measured at several locations of specimen and given by finite element simulation also showed good agreement. Therefore, it is indicated that the designed specimen can reasonably simulate the residual stress of circumferential butt welding of pipe.

• 한국안전학회지
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• 제24권1호
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• pp.7-13
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• 2009

The objective of this study is to design a laboratory specimen for simulating residual stress of circumferential butt welding between pipes. Specimen type and method to generate residual stress were proposed based on the review of prior studies and parametric finite element analysis. To prove the proposed specimen type and loading method, the residual stress was generated using the designed specimen by applying proposed method and was measured. The measured residual stress using X-ray diffraction reasonably agreed with the results of finite element analysis considered in the specimen design. Comparison of residual strains measured at several locations on the specimen and given by finite element simulation also showed good agreement. Therefore, it is indicated that the designed specimen in this study can reasonably simulate the axial residual stress of a circumferential butt welding of pipe.

• 한국생산제조학회지
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• 제19권1호
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• pp.26-32
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• 2010

SM45C steel rods using generally for machine components were selected and welded by butt-GMA welding method for this study. And then they were studied about characteristics of fatigue behavior and fracture surfaces by rotary bending test. Fatigue strength in weld zone present highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. The region of infinite life by Haigh diagram present highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. Fatigue cracks in unnotched specimens of base metal and weld zone introduce simultaneously from extensive out-side of circumferential cross-section and propagate to the other side indicating beach markings and dimples according to consolidation of fatigue cracks. Fatigue cracks in all of notched specimens introduce simultaneously in out-side of circumferential cross-section by high stresses and propagate to center of it indicating beach markings.

• 대한기계학회논문집A
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• 제37권11호
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• pp.1379-1386
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• 2013

본 논문에서는 용접부 중앙에 원주방향 관통균열이 있는 V-그루브 맞대기 용접 배관의 한계하중 해석을 수행하였다. V-그루브 맞대기 용접 배관이 그루브 각 $45^{\circ}$, $90^{\circ}$를 갖는 형상에 대한 한계하중 식을 제시하기 위해 용접 형상의 변화에 따른 용접부 너비를 정의하였고 강도불일치 비, 용접부 너비, 균열 길이 및 배관 반경 비에 대한 체계적인 변수 해석을 수행 하였다. 모재와 용접재는 탄성 완전소성재료로 가정하였으며 상불일치와 하불일치 조건에서의 인장 하중과 굽힘 하중에 대한 강도불일치 한계하중이 강도불일치 비($M_F$)와 형상변수(${\psi}$)를 통해 정량화 됨을 유한요소 해석을 통해 확인하였다.

• 한국안전학회지
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• 제16권3호
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• pp.26-30
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• 2001

Creep crack growth lift of high temperature pressure equipments was assessed for various crack locations and for various material properties. Surface cracks at the inner and outer surface of the vessel in the axial and circumferential directions were considered. The crack was located in the weld metal, in the parent metal or at the weld interface. Results shored that the crack at the weld interface was the most dangerous one. The crack located outside is weaker than that located inside. Safety factors of the case in which improper material properties were used the to unavailability of the correct material properties were discussed.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2949-2957
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• 2020

Fatigue crack growth model has been developed for dissimilar metal weld joints of a piping component under cyclic loading, where in the crack is located at the center of the weld in the circumferential direction. The fracture parameter, Stress Intensity Factor (SIF) has been computed by using principle of superposition as K_H + K_M. K_H is evaluated by assuming that, the complete specimen is made of the material containing the notch location. In second stage, the stress field ahead of the crack tip, accounting for the strength mismatch, the applied load and geometry has been characterized to evaluate SIF (K_M). For each incremental crack depth, stress field ahead of the crack tip has been quantified by using J-integral (elastic), mismatch ratio, plastic interaction factor and stress parallel to the crack surface. The associated constants for evaluation of K_M have been computed by using the quantified stress field with respect to the distance from the crack tip. Net SIF (K_H + K_M) computed, has been used for the crack growth analysis and remaining life prediction by Paris crack growth model. To validate the model, SIF and remaining life has been predicted for a pipe made up of (i) SA312 Type 304LN austenitic stainless steel and SA508 Gr. 3 Cl. 1. Low alloy carbon steel (ii) welded SA312 Type 304LN austenitic stainless-steel pipe. From the studies, it is observed that the model could predict the remaining life of DMWJ piping components with a maximum difference of 15% compared to experimental observations.