DIFFERENT SOLUTIONS FOR STRESS AND STRAIN FIELDS IN AUTOFRETTAGED THICK-WALLED CYLINDERS

In the first part of the paper we will present an analytical solution to the plastic stress and strain distribution induced by a single over -pressure cycle in a cylindrical vessel. The solution is valid for mat erials which, during the loading phase, can be described by a linear h ardening law as well as by the modified Ramberg-Osgood law. We will cl arify the conditions for which the stress field expressions can be sim plified, thus facilitating a parametric analysis of their increase wit h respect to the values one would obtain when considering an ideal ela stic-perfectly plastic behaviour of the material. In the second part o f the paper, residual stress fields will be numerically evaluated, tak ing into account, during the unloading phase, both the variability of the stress flow and the Bauschinger effect factor as a function of pre -strains. (C) 1997 Elsevier Science Ltd.