FATIGUE AND CORROSION FATIGUE LIFE ASSESSMENT WITH APPLICATION TO AUTOFRETTAGED PARTS

摘要

This study investigates an effect of autofrertage on the fatigue and corrosion fatigue life of high pressure parts made from low carbon structural steel. To estimate the beneficial effect of autofrertage application, an extensive experimental program and advanced theoretical modelling are conducted and analyzed in this study. Accurate calculation of compressive residual stresses is achieved by application of a cyclic plasticity model which can precisely simulate a cyclic plasticity response of material. In terms of a fatigue life prediction methodology, a non-local stress based approach with a modified critical distance theory is used for prediction of the crack initiation stage providing conservative fatigue assessment. Because of the fact that the crack propagation stage can take a considerable part of the total life for autofrettaged parts, more accurate fatigue life calculation is performed by the use of a fracture mechanics approach. The total fatigue life time of autofrettaged parts is then calculated as a sum of the crack initiation and propagation stages.