Abstract
For high pressure reactor vessels such as for polyethylene production, autofrettage is used extensively to have the fatigue life elongated. In this study, to evaluate the material degradation based on the autofrettaged strain, the repeated internal pressure fatigue tests were conducted using the actual reactors, where the effect of autofrettage on the fatigue crack growth rate was investigated.
(1) Fatigue crack growth rate of the autofrettaged cylinder is smaller than that of the non-autofrettaged one, especially near the bore surface.
(2) Autofrettaged stain near the bore surface does not affect the material degradation, which means that the delay of fatigue crack growth rate is mainly caused by the highly compressive residual stress at the bore surface.
(3) The stress intensity factor expression of an autofrettaged thick cylinder was developed successfully which is based on the use of the effective stress intensity factor, Keff, considering the highly compressive residual stress.
