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Research Papers: Design and Analysis

Unified Solution of Burst Pressure for Defect-Free Thin Walled Elbows

[+] Author and Article Information
Y. Li

Department of Structural Engineering,
School of Civil Engineering,
Chang'an University,
197# Mailbox,
Xi'an, Shaanxi 710061, China
e-mail: liyanlwbdlp@126.com

J. H. Zhao

Department of Structural Engineering,
School of Civil Engineering,
Chang'an University,
197# Mailbox,
Xi'an, Shaanxi 710061, China
e-mail: zhaojh@chd.edu.cn

Q. Zhu

Department of Structural Engineering,
School of Civil Engineering,
Chang'an University,
197# Mailbox,
Xi'an, Shaanxi 710061, China
e-mail: Apple198731@126.com

X. Y. Cao

Department of Structural Engineering,
School of Civil Engineering,
Chang'an University,
197# Mailbox,
Xi'an, Shaanxi 710061, China
e-mail: caoxueye@126.com

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received January 9, 2014; final manuscript received July 18, 2014; published online October 15, 2014. Assoc. Editor: Spyros A. Karamanos.

J. Pressure Vessel Technol 137(2), 021203 (Oct 15, 2014) (7 pages) Paper No: PVT-14-1002; doi: 10.1115/1.4028068 History: Received January 09, 2014; Revised July 18, 2014

In order to study the mechanical properties of defect-free thin walled elbows (TWE), and evaluate impacts of the intermediate principal stress effect, tension/compression ratio, and strain-hardening of materials into logical consideration, this research, in the framework of finite deformation theory, derived the computational formula of burst pressure for defect-free TWE according to unified strength theory (UST). In addition, influences of various factors on burst pressure were analyzed, which include strength disparity (SD) effect of materials, intermediate principal stress, curvature influence coefficient, strain-hardening exponent, yield to tensile (Y/T) and thickness/radius ratio. The results show that the greater the tension/compression ratio is, the higher the burst pressure is. The influence of the SD effect of materials is more obvious with the increase of elbow curvature and intermediate principal stress. The intermediate principal stress effect can bring the self-bearing capacities and strength potential of materials into a full play, which can achieve certain economic benefits for projects. Moreover, the burst pressure of defect-free TWE increases with the growth of yield ratio and thickness/radius ratio, while decreases with the rise of curvature influence coefficient and strain-hardening exponent. It is also concluded that the Tresca-based and Mohr–Coulomb-based solutions of TWE are the lower bounds of the burst pressure, the twin shear stress (TSS)-based solution is the upper bound of the burst pressure, and the solutions based on the other yield criteria are between the above two. The unified solution in this paper is suitable for all kinds of isotropous materials which have the SD effect and intermediate principal stress effect. As the deduced formula has unified various burst pressure expressions proposed on the basis of different yield criteria for elbows of any curvature (including straight pipelines), and has established the quantitative relationships among them, its applicability is broader. Therefore, the unified solution is of great significance in security design and integrity assessment of defect-free TWE.

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Copyright © 2015 by ASME
Topics: Pressure , Stress , Pipes
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References

Figures

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Fig. 1

Yield loci on the π plane for UST (0 < α < 1)

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Fig. 2

Geometric dimension and mechanical model of TWSS

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Fig. 3

Relationship curves between pburst and b at different α

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Fig. 4

Relationship curves between pburst and α at different b

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Fig. 5

Relationship curves between pburst and β at different α

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Fig. 6

Relationship curves between pburst and β at different b

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Fig. 7

Relationship curves between pburst and n at different b

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Fig. 8

Relationship curves between pburst and Y/T at different b

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Fig. 9

Relationship curves between pburst and t0/r0 at different b

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