• 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.

• 한국정밀공학회지
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• 제8권1호
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• pp.41-49
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• 1991

A knowledge of the resdual stress distribution at circumferential weldments can normally increase the accuracy of a fracture assessment in pipe line. In this paper, we present the measurements about the residual stress distributions at three kinds of circumferential butt welded pipes using the holl drilling strain gage method. By this experiment, we have obtined the following characteristics. At the inner surface of the pipe region near the center line of welding is under high tensile residual stress. However, as the distance from the center line of welding increases, the tensile component decreases and finally becomes compressive residual stress at region far away from the center line of welding. The longitudinal residual stress at the outer surface is compressive regardless of the diameter of pipe and the circumferential stress is changed from compressive to tensile as pipe diameter increases. The results also demonstrate that the residual stress is mainly caused by self-restraint bending force in the pipe welding.

• 대한기계학회논문집
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• 제15권2호
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• pp.693-702
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• 1991

The existence of residual stress in the circumferential butt welded pipes is one of the most important problems concerning stress corrosion cracking in service. In this paper, the residual stress distributions in three kinds of circumferential butt welded pipes were measured by the hole drilling strain gage method and calculation using finite element method is performed and its results are compared with the experiments. At the inner surface of the pipe region near the center line of welding is under high tensile residual stress. However, as the distance from the center line of welding increases, the tensile component decreases and finally becomes compressive residual stress at region far away from the center line of welding. The longitudinal residual stress at the outer surface is compressive regardless of the diameter of pipe and the circumferential stress is changed rom compressive to tensile as pipe diameter increases. The results also demonstrate that the residual stress is mainly caused by self restraint bending force in the pipe welding.

• 한국자기학회지
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• 제13권2호
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• pp.76-81
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• 2003

매설된 송유관이나 가스관의 외부면과 내부면에 생성된 원형 결함(double circular pit) 부근에서 누설되는 자속 신호에 미치는 결함깊이와 인장응력(tensile stress)의 영향을 3차원 유한요소법을 이용하여 계산하였다. 배관의 축 및 방사상 방향의 누설자속 (Magnetic Flux Leakage: MFL) 신호는 배관 외$.$내부 면의 이중 결함깊이와 인장응력에 의해 영향을 받으며, 결함의 깊이가 깊어질수록 인장응력이 커질수록 MFL 신호는 증가하였다. 그러나 원주 방향의 MFL 신호는 결함깊이와 인장응력에 거의 영향을 받지 않았다.

• 대한기계학회논문집A
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• 제24권10호
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• pp.2513-2519
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• 2000

Free vibration characteristics of an initially stressed CD/DVD disk, which is designed for increasing critical speeds of current optical disks, are analyzed using the Rayleigh-Ritz technique based on variational formulations. Natural frequencies of the new disk depend on membrane stresses caused by disk rotation as well as residual stresses imposed during the cooling process of the injection molding. Critical speeds are calculated for the various initial patterns of radial and circumferential stresses. Initially imposed tensile stresses increase the natural frequencies of all the vibration modes except zero nodal diameter mode, whose natural frequency is independent of circumferential stress. A new disk with initial tensile stress of 0.5MPa is shown to have its critical speed about 30 % higher than the current optical disk.

• Geomechanics and Engineering
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• 제39권1호
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• pp.43-54
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• 2024

Cross-flaws are frequently encountered in practical rock engineering projects near horseshoe-shaped cavities, and their presence can significantly impact the failure mode of these cavities. This study utilizes a combination of laboratory experiments and numerical simulations to investigate the influence of cross-flaws on the failure mode of a horseshoe-shaped cavity. During the experimental tests, we varied the length of secondary flaw and the angle of the cross-flaws in the specimens, followed by subjecting them to biaxial compression. Our experimental results show that when the angle α between the primary and the secondary flaws is small (0° and 45°), only one crack is initiated at the vault of the cavity, resulting in a shear failure mode. Conversely, when the angle α is large (90° and 135°), two cracks are more likely to initiate at the vault of the cavity, leading to the failure mode of falling blocks in the surrounding rock. Furthermore, the circumferential stress at the cavity vault from numerical simulations results is consistent with this observed phenomenon. When the angle α is small, only one circumferential tensile stress concentration is observed at the cavity vault, resulting in the initiation of a single crack. In contrast, when the angle α is large, two stress concentrations appear at the vault of the cavity, leading to the initiation of two cracks from these locations.

• Journal of the Korean Wood Science and Technology
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• 제36권2호
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• pp.20-28
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• 2008

This study was carried out to provide the so-called circumferential slicing method for investigating radial distributions of the tangential strains and of moisture contents within the log cross section (LC) of Kalopanax pictus during indoor drying it. While the heartwood showed an almost uniform moisture content distribution in the range of about 50~55% in case of the green wood, it has gradually decreased toward the outer side, showing about 19% of moisture content difference from the innermost slice. Although the moisture gradient along the radial direction has gradually become gentle as drying progresses, the sapwood of the outer side represented the moisture contents below the fiber saturation point after 24 hours of drying while the heartwood in the inner part showed the moisture contents higher than the fiber saturation point. The pith side was laid under the tensile stress after 24 hours of drying, and then gradually decreasing toward the bark side, and showed the distribution being switched again to the tensile stress on the bark side. As the drying has progressed, this trend got more intensified, and finally showed the U-shaped distribution model after 48 hours of drying. The circumferential slice test is considered to be suitable in quantitatively determining the tangential strains and moisture content within a LC.

• Structural Engineering and Mechanics
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• 제47권1호
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• pp.131-147
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• 2013

In this paper, constraint-based fracture mechanics analyses of hollow cylinders with internal circumferential crack under tensile loading are conducted. Finite element analyses of the cracked cylinders are carried out to determine the fracture parameters including elastic T-stresses, and fully-plastic J-integrals. Linear elastic finite element analysis is conducted to obtain the T-stresses, and elastic-plastic analysis is conducted to obtain the fully plastic J-integrals. A wide range of cylinder geometries are studied, with cylinder radius ratios of $r_i/r_o$ = 0.2 to 0.8 and crack depth ratio a/t = 0.2 to 0.8. Fully plastic J-integrals are obtained for Ramberg-Osgood power law hardening material of n = 3, 5 and 10. These fracture parameters are then used to construct conventional and constraint-based failure assessment diagrams (FADs) to determine the maximum load carrying capacity of cracked cylinders. It is demonstrated that these tensile loaded cylinders with circumferential cracks are under low constraint conditions, and the load carrying capacity are higher when the low constraint effects are properly accounted for, using constraint-based FADs, comparing to the predictions from the conventional FADs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.529-534
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• 1998

To find out an adequate failure criterion in two-dimensional linear elastic crack problems, finite element programs, SED, which determine stress intensity factors $K_I, K_{II}$, crack angle and peak load by the minimum strain energy density failure criterion were developed. In this program, the conventional quadratic isoparametric elements were used in all regions except the crack tip zone where triangular singular elements with 6 nodes were used. The results of SED were compared with the results of those which followed by the maximum circumferential tensile stress criteria and those by the maximum energy release rate criteria and those by Jenq and Shah`s experiments of the same geometry and material properties. The maximum energy release rate criteria were better close to those of the Jenq and Shah`s experiments than the maximum circumferential tensile stress criteria and the minimum strain energy density criteria.

• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.101-108
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• 2021

To date, a number of stress intensity factor (SIF) solutions have been proposed for the cylindrical structure with circumferential through-wall cracks. However, each solution has a different format as well as applicable range. It is also known that there is a significant difference in predicted SIF values depending on the shape of the structure and the size of the crack. In this study, the applicability of various SIF solutions was analyzed by comparing the finite element analysis results for the case where a tensile load is applied to the cylindrical structure with circumferential through-wall crack. It is found that the calculated SIF gradually decreases and converges to a certain value with increasing length-to-radius ratio. Therefore, an appropriate length-to-radius ratio should be set in consideration of the dimensions of the actual cylindrical structure. For piping with sufficiently long cylinder, the ASME solution is found to be the most appropriate, and for a short cylinder, the API solution should be applied. On the other hand, the WEC solution requires careful attention to its application.