Reverse autofrettage involves the application of pressure to the OD of a tube which in turn produces bore yielding and a residual stress profile equal in magnitude but opposite in sign to conventional autofrettage.
The analyses within this paper identify two potential new manufacturing procedures involving reverse autofrettage. The procedures are predicted to reduce external tensile hoop stress in an autofrettaged gun tube. This reduction should increase lifetime of tubes that are prone to OD fatigue or corrosion-related failure from manufacturing defects or notches.
The first procedure involves traditional autofrettage of an inner tube and reverse autofrettage of a larger outer tube. The outer tube is then compounded with the inner tube by thermal shrink-fitting or some equivalent process. The second procedure employs a monobloc tube which is subjected to reverse autofrettage followed by conventional internal autofrettage. Both procedures significantly reduce OD residual hoop stress but in the case of the monobloc tube there is an associated loss of compressive residual bore hoop stress.
