Estimation of optimum rotational speed for rotational autofrettage of disks incorporating Bauschinger effect

Abstract

Rotational autofrettage is one of the new and potential methods for strengthening thick-walled hollow circular disks/cylinders against internal pressure, thermal gradient, and rotational speed in service. The method makes use of the centrifugal force resulting from the high speed rotation of the disk/cylinder to induce plastic deformation at its inner side. On subsequent unloading of the centrifugal force, beneficial residual stresses are set up in the disk/cylinder. In this article, the method of rotational autofrettage employed in the disks is optimized. The rotational autofrettage is treated for an elastic–perfectly plastic axisymmetric disk incorporating Bauschinger effect. The best rotational speed is estimated to accomplish the procedure of rotational autofrettage in the disk such that the maximum stress level induced in the disk is minimized upon loading in service. To minimize the hoop/equivalent stress in the rotationally autofrettaged disk during loading in service, a one-dimensional optimization procedure, internal halving method is used.