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Research Papers: Design and Analysis

Theoretical Analysis of Hydraulically Expanded Tube-to-Tubesheet Joints With Linear Strain Hardening Material Behavior

[+] Author and Article Information
Nor Eddine Laghzale

Department of Mechanical Engineering, Ecole de Technologie Superieure, 1100 Rue Notre-Dame Ouest, Montreal, QC, H3C 1K3, Canadalagnore@yahoo.com

Abdel-Hakim Bouzid

Department of Mechanical Engineering, Ecole de Technologie Superieure, 1100 Rue Notre-Dame Ouest, Montreal, QC, H3C 1K3, Canadahakim.bouzid@etsmtl.ca

J. Pressure Vessel Technol 131(6), 061202 (Oct 08, 2009) (8 pages) doi:10.1115/1.4000197 History: Received June 01, 2008; Revised May 02, 2009; Published October 08, 2009

The mechanism of failure of tube-to-tubesheet joints is related to the level of stresses produced in the tube expansion and transition zones during the expansion process. Maintaining a lower bound limit of the initial residual contact pressure over the lifetime of the expanded joint is a key solution to a leak free joint. An accurate model that estimates these stresses can be a useful tool to the design engineer to select the proper material geometry combination in conjunction with the required expansion pressure. Most existing design calculations are based on an elastic perfectly plastic behavior of the expansion joint materials. The proposed model is based on a strain hardening with a bilinear material behavior of the tube and the tubesheet. The interaction of these two components is simulated during the whole process of the application of the expansion pressure. The effects of the gap and the material strain hardening are to be emphasized. The model results are validated and confronted against the more accurate numerical finite element analysis models. Additional comparisons have been made to existing methods.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Expansion pressure sequence

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Figure 2

Plane strain FE models

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Figure 3

Radial stress variation during expansion: case of expansion without tubesheet plastic deformation

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Figure 4

Tangential stress variation during expansion: case of expansion without tubesheet plastic deformation

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Figure 5

Equivalent stress variation during expansion: case of expansion without tubesheet plastic deformation

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Figure 6

Radial stress variation during expansion: case of expansion with tubesheet plastic deformation

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Figure 7

Tangential stress variation during expansion: case of expansion with tubesheet plastic deformation

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Figure 8

Equivalent stress variation during expansion: case of expansion with tubesheet plastic deformation

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Figure 9

Residual contact pressure variation with initial clearance

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Figure 10

Residual contact pressure variation with tube tangent modulus without plastic deformation of tubesheet (Pe max=270 MPa and Syt=Sys=248 MPa)

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Figure 11

Required expansion pressure to achieve a residual contact pressure of 20 MPa

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Figure 12

Residual contact pressure variation with tube and tubesheet

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Figure 13

Residual contact pressure variation with tube and tubesheet tangent modulus (Pe max=273 MPa, Syt=248 MPa, and Sys=180 MPa)

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Figure 14

Percentage of thickness reduction during the expansion process of case 2

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