Assessment of creep behaviour of a narrow gap weld

Finite element creep analyses have been performed using Norton's secondary creep law and continuum damage equations for a thick-walled narrow gap pipe weld. The creep stress and failure life were obtained using combinations of material properties which allowed different strengths for the parent material, heat-affected zone and weld metal for 1/2Cr1/2Mo1/4V:2 1/4Cr1Mo welds. The stationary-state failure prediction was performed based on a steady-state rupture stress. The failure times obtained from continuum damage modelling were used for assessing the results and the accuracy of the steady-state approach. The results show that the creep stress and failure life of the narrow gap weldments of both materials data options were similar to those of the V-shaped weldments over a range of narrow gap weld widths from 8 to 12 mm. The conservatism of the steady-state analysis method is illustrated, from the life estimates. The data also allow estimation of a possible effect of the presence of a weld in a plain pressurised pipe. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.