In recent years considerable progress has been made in research work addressing the behaviour of defects at elevated temperature. Developments have been made both in structural assessment techniques and in methods for analysing representative materials data. On the basis of these developments a procedure has been produced within the CEGB for the assessment of defects in plant operating in the creep range under loadings for which creep rather than creep-fatigue is the dominant failure mechanism. This paper describes the CEGB procedure. Calculations are required for three events: the time for overall structural failure by continuum damage mechanisms; the time for incubation prior to crack extension; and the time for subsequent growth to a maximum tolerable defect size. Methods are presented for calculating these times and for obtaining the materials data required to perform the calculations.

Cegb assessment procedure for defects in plant operating in the creep range

Failure assessment diagrams for high temperature defect assessment

The influence of plasticity in creep crack growth in steels

Using a Strain Based Failure Assessment Diagram for Creep-Brittle Materials

The creep crack propagation behavior of a Cr−Mo−V rotor steel has been investigated at 538°C using time-dependent fracture mechanics concepts. The creep crack propagation lives and the creep deflection rates of double-edge-notched (DEN) specimens were estimated using previous data from compact-type specimens. The predicted crack growth lives and deflection rates compared favorably with the experimental data. When plotted as a function of the C

 t
 parameter, the experimentally determined creep crack propagation rates of DEN specimens were found to be in agreement with those of compact and center-crack-tension specimens. These results provide further experimental verification for the validity of the C

 t
 parameter for characterizing creep crack growth behavior. Some discrepancies between the predicted and the observed behavior are attributed to primary creep deformation behavior which was not considered in estimating the value of C

 t
 .

Crack propagation behavior under creep conditions

Creep crack growth tests have been performed on compact tension specimens of 2 1/4CrlMo, C—Mn, and AISI 316 weld metals at 565°C, at 360 and 390°C, and at 600°C, respectively. The data have...

D J Gooch

Papers

C∗ correlations for creep crack growth in weld metals