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The influence of residual stress distributions on the stress intensity factors developed in thick-walled cylinders containing line cracks is quantified. A stress intensity factor caused by the residual stress field, Kres, is evaluated using the superposition principle. This can then be superposed on the stress intensity factor associated with the applied loading to give an effective stress intensity factor controlling crack growth.
Boundary integral equation and weight function methods are applied to determine Kres as a function of crack depth for internally and externally flawed as-received and autofrettaged cylinders with a diameter ratio of 2.07. Good agreement is obtained between the two approaches over the range of normalized crack depth 0 ≤ a/W ≤ 0.7 (a = crack length, W = specimen width). Actual measured residual stress distributions, as well as analytical residual stress fields for autofrettaged tubing obtained assuming elastic-perfectly plastic behavior and the von Mises and Tresca yield criteria, are investigated. The Kres caused by autofrettage residual hoop stresses is essentially negative for internal cracks and positive for external cracks. The Kres solutions for the experimentally measured and von Mises distributions compare very favorably. The results for the Tresca distribution are approximately twice as large and are considered to be too conservative.
autofrettage, residual stresses, linear-elastic fracture mechanics, stress intensity factor, superposition principle, weight functions
Structural engineer, Lloyd's Register, London,
Reader, Imperial College of Science and Technology, London,