Fatigue Strength Evaluation of Welded Joint in Pressure Vessel by Probabilistic Fracture Mechanics

Abstract

This paper describes the fatigue life estimation of the welded joint having an unpenetrated portion in the pressure vessel by use of the fracture mechanics. The internal pressure fatigue tests of the pressure vessel were carried out at room temperature and the stress intensity factor of welded joint was analyzed by the finite element method regarding the unpenetrated portion as a crack. The simple method for the probabilistic life prediction of the fatigue crack growth is presented by applying the first-order sensitibity analysis in the deterministic fracture mechanics approach. In the calculating procedure of life estimation, the size of the unpenetrated portion and the fatigue crack gowth rate obtained from the da/dN tests are regarded as the uncertain factors. Comparing the analytical results with the tests results, the validity of the present method is confirmed.