• Journal of Mechanical Science and Technology
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• 제14권11호
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• pp.1216-1224
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• 2000

The collapse pressure of tubes is determined experimentally by Tschoepe and Maison for various materials with different geometries. The results are compared with those obtained by ASME Codes UG-31 and UG-28. A collage pressure is the pressure required for the incipient yielding stress of the tubes with and without ovality. This collapse pressure is compared with the experimental results by Tschoepe and Maison. The present investigation is towards finding the collapse pressure required to bring the entire wall of tubes into a state of plastic flow for the pipes, with ovality and without ovality. This collapse pressure is compared with the collapse pressure obtained through experiments in the present investigation. The experimental results are compared with the pressure obtained by FEM(finite element methods). The FEM results are then compared with results obtained through an approximate plastic analysis of the strain hardening material, SA312-TP304 stainless steel. The structural integrity evaluation is performed for the heat exchanger used in an actual nuclear power plant by using various methods described in this paper. The results obtained by the various analyses and the FEM are discussed. consequently, the paper is oriented towards an actual design purpose of d heat exchanger in an industrial environment, rather than for the purpose of an academic research project investigation.

• Nuclear Engineering and Technology
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• 제42권4호
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• pp.450-459
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• 2010

The present paper investigates the collapse pressure of cylinders with intermediate thickness subjected to external pressure based on detailed elastic-plastic finite element (FE) analyses. The effect of the initial ovality of the tube on the collapse pressure was explicitly considered in the FE analyses. Based on the present FE results, the analytical yield locus, considering the interaction between the plastic collapse and local instability due to initial ovality, was also proposed. The collapse pressure values based on the proposed yield locus agree well with the present FE results; thus, the validity of the proposed yield locus for the thickness range of interest was verified. Moreover, the partial safety factor concept based on the structural reliability theory was also applied to the proposed collapse pressure estimation model, and, thus, the priority of importance of respective parameter constituting for the collapse of cylinders under external pressure was estimated in this study. From the application of the partial safety factor concept, the yield strength was concluded to be the most sensitive, and the initial ovality of tube was not so effective in the proposed collapse pressure estimation model. The present deterministic and probabilistic results are expected to be utilized in the design and maintenance of cylinders subjected to external pressure with initial ovality, such as the once-through type steam generator.

• 한국해양공학회지
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• 제13권4호통권35호
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• pp.82-97
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• 1999

A deep sea vehicle must be designed to ensure its safety under ultra-high pressure circumstances. If a pressure housing of a deepsea vehicle is collapsed by ultra-high pressure, the deepsea vehicle may be lost. The objective of this paper is to introduce a design collapse pressure for the deep sea pressure vessel which is composed of one cylinder and two hemispheres. Especially the collapse pressure of hemispherical shell with a hole at top is analyzed by a variational approach (weighted residual method). And for the purpose of design, the salty factor of collapse pressure is presented which is analyzed by interpolation method.

• Structural Engineering and Mechanics
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• 제18권5호
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• pp.627-644
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• 2004

In this study, the endochronic theory was used to investigate the collapse of thick-walled tubes subjected to external pressure and axial tension. The experimental and theoretical findings of Madhavan et al. (1993) for thick-walled tubes of 304 stainless steel subjected to external pressure and axial tension were compared with the endochronic simulation. Collapse envelopes for various diameter-to-thickness tubes under two different pressure-tension loadings were involved. It has been shown that the experimental results were aptly described by the endochronic approach demonstrated from comparison with the theoretical prediction employed by Madhavan et al. (1993). Furthermore, by using the rate-sensitivity function of the intrinsic time measure proposed by Pan and Chern (1997) in the endochronic theory, our theoretical analysis was extended to investigate the viscoplastic collapse of thick-walled tubes subjected to external pressure and axial tension. It was found that the pressure-tension collapse envelopes are strongly influenced by the strain-rate during axial tension. Due to the hardening of the metal tube of 304 stainless steel under a faster strain-rate during uniaxial tension, the size of the tension-collapse envelope increases.

• 한국해양공학회지
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• 제33권3호
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• pp.272-279
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• 2019

In order to perform a pressure chamber experiment with a circular cylindrical pressure vessel, the dimensions of the cylinder need to be determined in the range of the maximum externally applied pressure of the chamber to create the collapse process. In this study, the collapse load values from published chamber test results, finite element analysis and the theory of thick cylinders were thoroughly compared in a aluminum cylinder. In order to investigate the effect of collapse load according to the ovality during manufacturing, nonlinear buckling analysis was performed and the collapse load according to ovality was compared. Based on the results, the dimensions of the steel cylinder were determined for the future chamber collapse test.

• Earthquakes and Structures
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• 제3권3_4호
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• pp.473-494
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• 2012

The capacity of pipelines to resist collapse under external pressure and bending moment is a major aspect of deepwater pipeline design. Existing design codes present interaction equations that quantify pipeline capacities under such loadings, although reasonably accurate, are based on empirical data fitting of the bending strain, and assumed simplistic interaction with external pressure collapse. The rational model for collapse of deepwater pipelines, which are relatively thick with a diameter-to-thickness ratio less than 40, provides a unique theoretical basis since it is derived from first principles such as force equilibrium and compatibility equations. This paper presents the rational model methodology and compares predicted results and recently published full scale experimental data on the subject. Predictive capabilities of the rational model are shown to be excellent. The methodology is extended for the problem of pipeline collapse under point load, longitudinal bending and external pressure. Due to its rational derivation and excellent prediction capabilities, it is recommended that design codes adopt the rational model methodology.

• 대한조선학회논문집
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• 제56권2호
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• pp.175-186
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• 2019

Number of studies on the buckling of thin cylindrical pressure vessels, such as submarine pressure hull and pipe with a large ratio of diameter/thickness, have been carried out in the naval and ocean engineering. However, research about thick cylinder pressure vessel has not been active except for the specific application in nuclear area. There are not many papers for the estimation of buckling and ultimate load capacity of thick cylinders for the deep sea usage. Thus, it is important to understand the theoretical bases of the buckling and collapse process and the derivation process of such loads for the proper design and structural analysis. The objective of this study is to survey the collapse behavior, to analyse and clarify the derivation procedure and to estimate the ultimate collapse load for thick cylinder by analyzing relevant books and papers. It is found that the yielding begins at the internal surface of the thick cylinder and plasticity develops from the internal surface to the external surface to generate collapse. Also the initial imperfection of cylinder develops flattening and consequently accelerates buckling and finally ultimate collapse. By comparing the collapse loads of aluminum thick cylinder by applying equations herein, it is shown that the equations analyzed are appropriate to obtain collapse load for thick cylinder.

• 한국가스학회지
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• 제14권4호
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• pp.45-50
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• 2010

해저배관의 안전성 검토를 위하여 수압에 의한 소성붕괴 저항성을 평가하였다. 본 연구에서는 해저배관에 부가되는 주하중을 수압으로 설정하여 배관의 직경대 두께비와 ovality 변화가 배관의 소성붕괴 변화에 미치는 영향을 유한요소해석을 통하여 평가하였다. 내압은 외압에 의한 소성붕괴 저항성을 향상시켜 소성붕괴 발생 깊이를 증가시켰으며, 동일 ovality에서 local ovality를 갖는 배관은 global ovality 보다 더 깊은 붕괴 깊이를 나타내었으며, 소성붕괴 발생 깊이는 직경대 두께비의 증가 또는 ovality 증가에 따라 감소하였다.

• 한국가스학회지
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• 제15권6호
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• pp.14-19
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• 2011

원주 방향의 두께가 불균일한 해저배관에 대한 건전성을 검토하기 위하여 수압에 의한 소성붕괴 저항성을 평가하였다. 본 연구에서는 해저배관에 부가되는 주하중을 수압으로 설정하여 4, 8, 12 및 16%의 두께편차율을 갖는 API 5L X65와 API 5L X80 배관의 소성붕괴압력 변화에 미치는 영향을 유한요소해석을 통하여 평가하였다. 두께 편차율이 증가하면 소성붕괴압력이 감소하며 두께편차율이 동일하면 직경대 두께비가 증가함에 따라 소성붕괴 압력은 감소한다.

• Geomechanics and Engineering
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• 제7권5호
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• pp.553-567
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• 2014

Borehole instability during drilling process occurs frequently when drilling through shale formation. When a borehole is drilled in shale formation, the low permeability leads to an undrained loading condition. The pore pressure in the compressed area near the borehole may be higher than the initial pore pressure. However, the excess pore pressure caused by stress concentration was not considered in traditional borehole stability models. In this study, the calculation model of excess pore pressure induced by drilling was obtained with the introduction of Henkel's excess pore pressure theory. Combined with Mohr-Coulumb strength criterion, the calculation model of collapse pressure of shale in undrained condition is obtained. Furthermore, the variation of excess pore pressure and effective stress on the borehole wall is analyzed, and the influence of Skempton's pore pressure parameter on collapse pressure is also analyzed. The excess pore pressure decreases with the increasing of drilling fluid density; the excess pore pressure and collapse pressure both increase with the increasing of Skempton's pore pressure parameter. The study results provide a reference for determining drilling fluid density when drilling in shale formation.