Residual Stress Evaluation and Its Effects on the Fatigue Life of an Autofrettaged Tube

Abstract

The theoretical residual stresses in the autofrettaged tube were calculated, considering Bauschinger effect caused by the reverse yielding while removing autofrettage pressure. Actual residual stresses were measured by using X-ray diffraction analysis, and compared with the theoretical calculations. From the tension-compression tests, however, the tube steel showed a significant Bauschinger effect, depending on the plastic strain prior to unloading. Fatigue crack growth life of the tube was evaluated by integrating the crack growth rate equation. Stress intensity factor of an inside crack at the tube due to pressure and residual stresses was determined from finite element analysis and superposition principle. Compared to the unautofrettaged tube, the extended fatigue life of the autofrettaged thick-walled tube was obtained depending on the autofrettage level and the Bauschinger effect.