Bauschinger Effect Design Procedures for Compound Tubes Containing an Autofrettaged Layer

Abstract

Autofrettage is used to introduce advantageous residual stresses into pressure vessels. The Bauschinger effect can produce less compressive residual hoop stresses near the bore than are predicted by “ideal” autofrettage solutions. A design procedure was recently proposed which models material removal from the bore or outside diameter of a single, plain autofrettaged tube in the presence of Bauschinger effect. This paper extends the procedure to model the addition of pressure or of material (via shrink-fit) to the tube, providing associated residual stress profiles following various amounts of further yielding due to a net external pressure. Simple criteria are developed for determining, and avoiding, further yielding in the autofrettaged tube when it is used as part of a compound assembly involving shrink-fitting; these criteria are based upon net pressure differential between the bore and outside diameter of the autofrettaged tube. An alternative criterion, based upon bore hoop stress, is shown to be erroneous.