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Research Papers: Design and Analysis

Design Optimization of Compound Cylinders Subjected to Autofrettage and Shrink-Fitting Processes

[+] Author and Article Information
Ossama R. Abdelsalam

Ph.D. candidate
e-mail: ossama_ramy@yahoo.com

Ramin Sedaghati

Professor
FASME
e-mail: ramin.sedaghati@concordia.ca
Mechanical and Industrial Department,
Concordia University,
Montreal, Quebec H3G 1M8, Canada

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the Journal of Pressure Vessel Technology. Manuscript received July 11, 2012; final manuscript received October 12, 2012; published online March 18, 2013. Assoc. Editor: Mordechai Perl.

J. Pressure Vessel Technol 135(2), 021209 (Mar 18, 2013) (11 pages) Paper No: PVT-12-1094; doi: 10.1115/1.4007960 History: Received July 11, 2012; Revised October 12, 2012

The autofrettage and shrink-fit processes are used to increase the load bearing capacity and fatigue life of the pressure vessels under thermomechanical loads. In this paper, a design optimization methodology has been proposed to identify optimal configurations of a two-layer cylinder subjected to different combinations of shrink-fit and autofrettage processes. The objective is to find the optimal thickness of each layer, autofrettage pressure and radial interference for each shrink-fit, and autofrettage combination in order to increase the fatigue life of the compound cylinder by maximizing the beneficial and minimizing the detrimental residual stresses induced by these processes. A finite element model has been developed in ansys environment to accurately evaluate the tangential stress profile through the thickness of the cylinder. The finite element model is then utilized in combination with design of experiment (DOE) and the response surface method (RSM) to develop a smooth response function which can be effectively used in the design optimization formulation. Finally, genetic algorithm (GA) combined with sequential quadratic programming (SQP) has been used to find global optimum configuration for each combination of autofrettage and shrink-fit processes. The residual stress distributions and the mechanical fatigue life based on the ASME code for high pressure vessels have been calculated for the optimal configurations and then compared. It is found that the combination of shrink-fitting of two base layers then performing double autofrettage (exterior autofrettage prior to interior autofrettage) on the whole assembly can provide higher fatigue life time for both inner and outer layers of the cylinder.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Geometrical and finite element model of two-layered cylinder

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Fig. 2

Actual and bilinear kinematic stress–strain behavior

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Fig. 17

Fatigue life for the different combinations in case of requirement (c) for the inner and outer layers of the cylinder

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Fig. 16

Fatigue life for the different combinations in case of requirement (b) for the inner and outer layers of the cylinder

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Fig. 15

Fatigue life for different combinations in case of requirement (a) for the inner and outer layers of the cylinder

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Fig. 14

Residual hoop stress distribution through the cylinder thickness for the seventh combination

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Fig. 13

Residual hoop stress distribution through the cylinder thickness for the sixth combination

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Fig. 12

Residual hoop stress distribution through the cylinder thickness for the fifth combination

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Fig. 11

Residual hoop stress distribution through the cylinder thickness for the fourth combination

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Fig. 10

Residual hoop stress distribution through the cylinder thickness for the third combination

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Fig. 9

Residual hoop stress distribution through the cylinder thickness for the second combination

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Fig. 8

Residual hoop stress distribution through the cylinder thickness for the first combination

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Fig. 7

Maximum residual hoop stresses for different combinations-requirement (c)

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Fig. 6

Maximum residual hoop stresses for different combinations-requirement (b)

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Fig. 5

Maximum residual hoop stresses for different combinations-requirement (a)

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Fig. 4

Radial distribution of residual hoop stress for two-layer shrink-fitted cylinder

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Fig. 3

Residual hoop stress for a single layer autofrettage cylinder using the bilinear kinematic and the real models

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