A Simplified Method for Predicting the Creep Crack Growth in P91 Welds at 650 °C

Abstract

This article uses a numerical method for predicting the creep crack growth in compact tension (CT) specimens, including those containing welds. A series of incremental steady-state finite-element (FE) analyses were performed, using Norton's law to represent the creep behaviour, in order to simulate the progressive creep crack growth process. Validation of the FE predictions was achieved by comparing the creep crack growth test results obtained for parent material (PM) and cross-weld CT specimens removed from a P91 weld; the tests were carried out at 650 °C. Experimental results show that the creep crack growth rates for cross-weld specimens are higher than those for PM specimens by a factor of ˜4, for the same value of C*. Good agreement was obtained between the FE predictions and the experimental results for both the PM and cross-weld CT specimens. The FE results obtained using this approach are also in good agreement with those obtained from continuum damage analyses. The advantage of the proposed approach is that it requires much fewer material constants for use in the numerical predictions, compared with the damage mechanics approach.