Fatigue behaviour of an autofrettaged high-pressure vessel for the food industry

The autofrettage technique is commonly used to produce compressive tangential residual stresses near the bore of high-pressure vessels. These compression stresses improve the fatigue life of the vessel during the loading-unloading high-pressure cycles. The present paper presents the fatigue design of an autofrettaged thick-walled vessel for the food industry, working at an internal pressure of 500 MPa. A finite element analysis has been performed in order to obtain the residual stresses after the autofrettage at an internal pressure of 925 MPa. The material of the vessel was a 15-5PH 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. Finally, the fatigue life of the vessel was obtained using the residual stresses obtained in the previous simulations stage. (C) 2006 Elsevier Ltd. All rights reserved.