Creep continuum damage analysis for a pressurized thick wall circumferentially welded CrMoV steel pipe at 640

The failure assessment for thick wall CrMoV steel pipes circumferentially welded at 640°C was studied using the Finite Element (FE) method under close-ended, open-ended and axial compression conditions, respectively. The life and position of failure, redistribution of stress on the welds and damage variations were obtained using damage modeling. Since there is a distinct mismatch of mechanical properties in parent material, weld material and heat affect zone, variations of damage with time, stress redistribution and failure life in each zone are different. The FEM results show that the weakness of the welds is the heat-affected zone (HAZ) where the hoop stresses increase sharply in the tertiary stage of creep. The maximum of damage of the welds lies on the inner surface of in the weld zone when failure occurs. The information is useful for assessing the performance of practical service welds in power plants pipe work.