In-plane and out-of-plane unified constraint-dependent creep crack growth rate of 316H steel

• The unified creep constraint parameter Ac is analyzed along 3-D crack fronts.
• The unified constraint-dependent CCG rate equation of 316H steel has been obtained.
• The predicted CCG rate by the equation agrees well with the experimental data.
• The equation may be used in CCG life assessment incorporating any constraints.

The unified characterization parameter Ac of in-plane and out-of-plane creep constraints along three-dimensional crack front in different specimen geometries has been analyzed. Based on the parameter Ac and the experimental creep crack growth rate data of different specimen geometries in the literature, the in-plane and out-of-plane unified constraint-dependent creep crack growth rate equation of 316H steel has been obtained. The predicted creep crack growth rate by using the equation for each specimen agrees well with the experimental data. Based on the two-parameter C∗ − Ac concept, the equation may be used in creep crack growth life assessments incorporating in-plane and out-of-plane constraint effects.