Endurance limit of autofrettaged Diesel-engine injection tubes with defects

The endurance limit of cold drawn tubes under cyclic internal pressure has been investigated experimentally and numerically. Multiple specimen configurations regarding material state, defect depth and autofrettage pressures have been covered. The endurance limit can be increased considerably by autofrettage.Basic items of the proposed simulation method are the application of a plasticity model which is able to accurately describe all relevant deformation characteristics and a finite element based crack propagation calculation. Crack opening pressures and effective ranges of the stress intensity factor are calculated. The corresponding threshold condition yields the endurance limits. They are in good agreement with the experimental values.