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Research Papers: Design and Analysis

# Plastic Collapse Assessment Procedure for Vessel With Local Thin Area Simultaneously Subjected to Internal Pressure and External Bending Moment

[+] Author and Article Information
Shinji Konosu

Ibaraki University, Nakanarusawa Hitachi, Ibaraki 312-8511, Japan

Norihiko Mukaimachi

JGC Corporation, Yokohama 220-6001, Japan

J. Pressure Vessel Technol 130(1), 011207 (Jan 23, 2008) (10 pages) doi:10.1115/1.2827491 History: Received September 08, 2006; Revised January 16, 2007; Published January 23, 2008

## Abstract

Assessment of the local thin area should be undertaken for both tension and compression bending. In this paper, simplified reference stresses for a flaw in a cylinder are proposed. By using these results, a newly developed $p-M$ (internal pressure ratio and external bending moment ratio) diagram which can evaluate the collapse condition for pressure equipment such as vessels, piping, and storage tanks with a local thin area simultaneously subjected to internal pressure $p$ and external bending moment $M$ due to earthquake, etc., is proposed. The $p-M$ line is verified by comparison with the finite element analysis results and the numerous results of experiment for a cylinder with a volumetric flaw obtained through the reference literatures. It was clarified that the differences in collapse limit between the $p-M$ line and DNV guideline under both internal pressure and compression moment became evident where the outer diameter/wall thickness of a cylinder is large and the yield ratio of the material is small.

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## Figures

Figure 1

Surface flaw subjected to axial stress and moment with rotation restraint

Figure 2

External circumferential surface flaw

Figure 3

Comparison between exact reference stresses and approximation reference stresses for external circumferential flaw in a cylinder

Figure 4

Analysis region, load, and boundary condition of the cracklike flaw

Figure 5

FEM mesh of the cracklike flaw in the longitudinal direction

Figure 6

FEM mesh of the cracklike flaw in the circumferential direction

Figure 7

Analysis region, load, and boundary condition of the volumetric flaw

Figure 8

FEM mesh of the volumetric flaw

Figure 9

Figure 10

Figure 11

Load-displacement curve and collapse load due to moment under the design pressure of 1.128MPa

Figure 12

Safety margins in newly developed p-M diagram for cylinders with an external surface flaw when σf is assumed to be σysmin for carbon steels

Figure 13

Influence of Do∕t for cylinders on buckling modification factor, ηc

Figure 14

Comparison between p-M line and DNV guideline under both internal pressure and compression moment

## Errata

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