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Research Papers: Design and Analysis

Feasibility Study of Thermal Autofrettage of Thick-Walled Cylinders

[+] Author and Article Information
S. M. Kamal

Department of Mechanical Engineering,
Indian Institute of Technology Guwahati,
Guwahati 781039, India

U. S. Dixit

Department of Mechanical Engineering,
Indian Institute of Technology Guwahati,
Guwahati 781039, India
e-mail: uday@iitg.ac.in

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received October 20, 2014; final manuscript received March 7, 2015; published online June 9, 2015. Assoc. Editor: Mordechai Perl.

J. Pressure Vessel Technol 137(6), 061207 (Dec 01, 2015) (18 pages) Paper No: PVT-14-1168; doi: 10.1115/1.4030025 History: Received October 20, 2014; Revised March 07, 2015; Online June 09, 2015

Thick-walled cylinders such as gun barrels, high pressure containers, and rocket shells are designed to withstand high pressure. The cylinder material may crack if the induced pressure exceeds the material yield strength. Therefore, the thick-walled cylinders are autofrettaged in order to withstand very high pressure in service condition. The most commonly practiced autofrettage processes are hydraulic autofrettage and swage autofrettage. Hydraulic autofrettage involves very high internal pressure at the bore of the cylinder, and in swage autofrettage an oversized mandrel is pushed through the cylinder bore to cause the plastic deformation of the inner wall of the cylinder leaving the outer wall at the elastic state. This results in compressive residual stresses at and around the inner wall of the cylinder, which reduces the maximum stress in the cylinder during next stage of loading by pressurization. Both the processes are well established, but still there are certain disadvantages associated with the processes. The present work proposes a novel method of autofrettage for increasing the pressure carrying capacity of thick-walled cylinders. The method involves only radial temperature gradient in the cylinder for achieving autofrettage. The proposed process is analyzed theoretically for thick-walled cylinders with free ends. The numerical simulations of the process for typical cases and preliminary experiments show encouraging results for the feasibility of the proposed autofrettage process.

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References

Figures

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Fig. 1

Experimental setup for thermal autofrettage: (a) photograph and (b) schematic diagram

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Fig. 2

The elastic and plastic zones in the cylinder: (a) first stage and (b) second stage

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Fig. 4

Residual stresses in the aluminum cylinder

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Fig. 6

Elastic–plastic stress distribution in SS304 cylinder

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Fig. 7

Residual stresses in SS304 cylinder

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Fig. 3

Elastic–plastic stress distribution in aluminum cylinder

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Fig. 5

Stress distribution in the aluminum cylinder with and without autofrettage

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Fig. 8

Stress distribution in SS304 cylinder with and without autofrettage

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Fig. 9

Residual stresses in aluminum cylinder for both thermal and hydraulic autofrettage

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Fig. 10

Residual stresses in SS304 cylinder for both thermal and hydraulic autofrettage

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Fig. 11

Comparison of analytical stress distributions with 3D FEM: (a) without strain hardening and (b) with strain hardening for aluminum cylinder

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Fig. 12

Comparison of analytical stress distributions with 3D FEM: (a) without strain hardening and (b) with strain hardening for SS304 cylinder

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