Prediction of creep crack initiation time based on constraint parameters in specimens with different geometries

Based on two creep constraint parameters (R* and A(c)), the constraint-dependent creep crack initiation (CCI) time equations of a Cr-Mo-V steel at 566 degrees C have been established over a wide range of C* region. The equations are independent on the choice of the reference specimen. Based on the two-parameter (C*-R* and C*-A(c)) and the constraint-dependent CCI time equations, the CCI time for the specimens with different geometries and dimensions (with a wide range of constraint levels) has been predicted over a wide range of C* region. The predicted CCI time agrees well with experimental data available and CCI time of finite element simulations based on the creep ductility exhaustion model. The specimen geometry with high constraint strengthens the effect of out-of-plane constraint on the CCI time. The two constraint parameters R* and A(c) can give similar CCI time prediction results. The two-parameter approaches with considering constraint effect may be applied in the CCI life assessment of high-temperature components (such as pressure pipes and vessels) under static loads in operating plants.

Automated summary

The study established creep crack initiation time equations for a Cr-Mo-V steel at 566 degrees C under different constraints, and predicted crack initiation times for specimens with different geometries and dimensions under various constraint levels. The predictions aligned well with experimental data and finite element simulations, suggesting the applicability of the methods for high-temperature components under static loads.