Reverse Yielding and Bauschinger Effect on Residual Stresses in Thick-walled Cylinders

M. Moradi, A. Ghorbanpour, H. Khademizadeh and A. Loghman

A thick- walled cylinder of isotropic, homogeneous, strain hardening material with closed ends, which is assumed obey Von-Mises yield criterion is considered in this study. Loading is also assumed to consist of a temperature gradient as well as an internal pressure. A generalized plane strain case in which the material obeys Von Mises criterion is studied. Von-Mises yield criterion is generalized as a function of several dimensionless variables such as thickness ratio, temperature gradient, inner pressure and radius. Critical conditions for a wide range of loading combinations and thickness ratios are investigated. After the critical condition is established, load is increased beyond the critical values, plastic stresses and progress of plastic zone are calculated using an incremental theory of plasticity. Results of residual stress distributions with an without the Bauschinger effect factor(BEF) are compared and the BEF on the predictions of reverse yielding is investigated. It is concluded that for specific cylinder (radii ratio β=2), subsequent residual stresses, for a 45% overstrained condition, are at the onset of reverse yielding when the BEF is taken into account; while residual stresses resulted from unloading the same cylinder at a fully plastic over strained condition exhibit otherwise in the case of BEF is ignored.

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