Creep fracture parameter C solutions for axial internal and external surface cracks in pressurized cylinders

•The C* solutions for internal and external axial surface cracks in pressurized cylinders are investigated.•Creep influence function for calculating C* along the crack fronts is obtained and fitted into formulas.•The correlation equations between C* and creep hardening exponent n are firstly developed.•Effects of crack sizes and cylinder geometries on the C* distributions along the crack fronts are analyzed. Accurate calculations of creep fracture mechanics parameter C* is very important for life prediction and assessment of high-temperature cracked components. The current two engineering estimation approaches (EPRI and reference stress approaches) for C* can seriously overestimate or sometimes underestimate C* of cracked components, thus it is desirable to develop accurate C* solutions. In this work, based on extensive three-dimensional (3D) finite element analyses, the C* solutions for axial internal and external surface cracks with a wide range of sizes in pressurized cylinders with different geometry sizes are investigated and developed. The creep influence function Hc for calculating C* along the crack fronts has been obtained and fitted into equations, and the accuracy of the equations has been verified. The correlation equations between C* and creep hardening exponent n are firstly developed which can be conveniently used to estimate C* for materials with different n values. The effects of crack sizes and cylinder geometries on the C* distributions along the crack fronts also are analyzed.