Simplified estimates of the creep crack growth parameter C(t) under primary/secondary stresses using the enhanced reference stress method

This paper describes simplified methods to estimate the fracture mechanics parameter, C(t), related to creep crack growth rates in non-steady state creep conditions produced by primary or secondary stresses. The methods proposed incorporate effects from initial plasticity and redistribution during a short period after a loading dwell starts, in addition to the estimate of the steady state creep crack growth parameter C∗ by the enhanced reference stress method. The methods have been validated by performing finite element elastic–plastic creep analyses of a circumferentially cracked cylinder subjected to load-controlled tension or thermal loads.