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RESEARCH PAPERS

Optimum Autofrettage and Shrink-Fit Combination in Multi-Layer Cylinders

[+] Author and Article Information
Hamid Jahed1

Mechanical Engineering Department,  Iran University of Science and Technology, Tehran, Iran 16844hjahedmo@uwaterloo.ca

Behrooz Farshi

Mechanical Engineering Department,  Iran University of Science and Technology, Tehran, Iran 16844farshi@iust.ac.ir

Morvarid Karimi

Mechanical Engineering Department,  Iran University of Science and Technology, Tehran, Iran 16844

1

Presently, Associate Professor, Mechanical Engineering Department, University of Waterloo, 200 University Ave W., Waterloo, Ontario N2L 3G1, Canada.

J. Pressure Vessel Technol 128(2), 196-200 (Dec 08, 2005) (5 pages) doi:10.1115/1.2172957 History: Received November 27, 2005; Revised December 08, 2005

The interest in the use of layered cylinders that combine autofrettage and shrink fit in order to extend fatigue lifetimes is increasing. As the number of layers increases, the sequential order of assembly and the size of each layer become more important. To achieve the most benefical result, a design optimization method is required. In this investigation, the optimum design of a three-layered vessel for maximum fatigue life expectancy under the combined effects of autofrettage and shrink fit has been considered. To obtain optimum size of each layer and to optimize the initial stress distribution, the numerical optimization procedure known as the Simplex search method is employed here. The thickness of each layer, shrink-fit pressures, and autofrettage percentages are treated as design variables. Under stress constraints, the operational sequences for assembly of a layered vessel have been formulated in order to lead to optimum results, defined as maximum life expectancy. The fatigue life consideration is based on ASME code provisions and standards for high pressure vessel technology, which define the allowable final crack depth for multilayer vessels. The proposed procedure has been carried out on a number of examples. The results show that, with proper combination of operations significant life enhancement can be achieved using the optimization procedure.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Simplex method for a 2D problem

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Figure 2

Three-layer vessel considered in this study

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Figure 3

Engineering stress strain plots of A723‐1130MPa, after, Ref. 14

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Figure 4

Unloading reloading behavior of A723‐1130MPa, after, Ref. 14

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Figure 5

Residual hoop stresses in case 1

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Figure 6

Total stresses upon application of the service load in case 1

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Figure 7

Residual hoop stresses in case 2

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Figure 8

Total stresses upon application of the service load in case 2

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Figure 9

Residual hoop stresses in case 3

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Figure 10

Total stresses upon application of the service load in case 3

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