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Stress intensity, stress concentration and fatigue crack growth along evacuators of pressurized, autofrettaged tubes

Book ·
OSTI ID:124726
 [1];  [2]
  1. Univ. of Northumbria, Newcastle (United Kingdom)
  2. Army Armament Research, Development and Engineering Center, Watervliet, NY (United States)
The geometry analyzed consists of a thick-walled cylinder having a small diameter evacuator hole penetrating radially through the wall. The loading involves pressure acting on the ID of the tube and all or part of this pressure acting on the evacuator hole. In addition the tube may be fully or partially autofrettaged. Total hoop stress concentrations are determined for a range of radial locations along the evacuator, as are stress intensity factors along a crack emanating from the evacuator hole. Fatigue crack growth rates, and hence crack profiles, are predicted at each of the radial locations. These predictions indicate that the critical location for the crack in a non-autofrettaged tube is at the ID whereas in a fully autofrettaged tube it is located approximately half way through the wall thickness. Taking account of the influence of stress ratio, minimum value of direct stress/maximum value of direct stress has a significantly influence on crack shape in autofrettaged tubes, but a limited effect upon lifetime. The effect upon fatigue lifetime of axial residual stresses due to the autofrettage process is described and it is demonstrated that an insignificant reduction in lifetime results from the presence of such stresses. Finally the predicted profiles are compared with experimental observations of fatigue cracked evacuators and a limited comparison of predicted and actual lifetimes is presented. Agreement is considered good.
OSTI ID:
124726
Report Number(s):
CONF-950740--; ISBN 0-7918-1332-0
Country of Publication:
United States
Language:
English