The Bauschinger Effect's Impact on the 3-D Combined SIFs for Radially Cracked Fully or Partially Autofrettaged Thick-Walled Cylinders
M. Perl; C. Levy; and V. Rallabhandy

Source CMES: Computer Modeling in Engineering & Sciences, Vol. 11, No. 1, pp. 37-48, 2006
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Keywords Bauschinger Effect, Autofrettage, Pressure Vessel.
Abstract The Bauschinger Effect (BE) impact on$K_{IN }$-- the combined, Mode I, 3-D Stress Intensity Factor (SIF) distributions for arrays of radial, internal, surface cracks emanating from the bore of a fully or partially autofrettaged thick-walled cylinder is investigated. A in-depth comparison between the combined SIFs for a ``realistic'' - Bauschinger Effect Dependent Autofrettage (BEDA) and those for an ``ideal'' - Bauschinger Effect Independent Autofrettage (BEIA) is performed. The 3-D finite element (FE) analysis is performed employing the submodeling technique and singular elements along the crack front. Both autofrettage residual stress fields, BEDA and BEIA, are simulated using an equivalent temperature field and more than 1200 different crack configurations are analyzed. SIFs for numerous crack arrays, \textbf {n}, a wide range of crack depth to wall thickness ratios, \textbf {a/t}, various ellipticities, \textbf {a/c}, several values of the yield-stress to pressure ratio, \textbf {$\psi$}, and different levels of autofrettage, \textbf {$\varepsilon$}, are evaluated. Autofrettage efficiency, \textbf {$\eta$}, for all BEDA cases is determined, and is compared with that of BEIA. The largest combined SIF$K_{Nmax}$ is found to vary with angular location along the crack front and number of cracks and therefore needs to be evaluated for each particular case. The Bauschinger Effect is found to have a dramatic detrimental impact on the fatigue life of the thick-walled cylinder. For a partially autofrettaged thick-walled cylinder,$\varepsilon<$="" 100{\%},="" it="" is="" found="" that="" the="" lower="" the="" level="" of="" autofrettage,="" the="" smaller="" the="" bauschinger="" effect="" is.="" increasing=""$\varepsilon=""$="" beyond="" 60{\%}="" is="" found="" to="" be="" counterproductive="" and="" is="" not="">
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