Design of an autofrettaged high-pressure vessel, considering the Bauschinger effect

Abstract

High-pressure processing is a method by which food products are subjected to a high level of hydrostatic pressure for a certain period of time. To achieve this process, it is necessary to correctly design high-pressure vessels capable of supporting at least 100 000 loading—unloading high-pressure cycles. The autofrettage technique is commonly used to produce compressive tangential residual stresses near the bore, which improve the fatigue life of the pressure vessel. This article shows the design of an autofrettaged thick-walled vessel that works at an internal pressure of 500 MPa, with an internal diameter of 300 mm and a length of 4500 mm. A finite element (FE) analysis was performed to obtain the residual stresses after the autofrettage at an internal pressure of 925 MPa. The material of the vessel was a 15–15 PH stainless steel hardened by precipitation, which shows a strong Bauschinger effect. For FE simulations, the material has been modelled considering an elastic—perfectly plastic behaviour for the loading phase and a Ramberg—Osgood behaviour for the unloading phase, with its coefficients depending on the previous equivalent plastic strain reached during the loading process. The simulation procedure is explained in detail and the results allow it to be applied for other autofrettage designs that need the Bauschinger effect of the material to be considered.