Numerical investigation of creep crack initiation in P92 steel pipes with embedded spherical defects under internal pressure at 650 °C

•We propose a new parameter-the average equivalent stress.•The assessment function for creep crack initiation position is obtained.•The assessment function for creep crack incubation time is obtained.

Creep crack initiation position and incubation time of P92 steel pipes with embedded spherical defects at 650 °C were investigated with finite element method. The function for the relationship between creep crack initiation position and the geometric parameters was obtained by fitting methods. The average equivalent stress was proposed to characterize the stress variation throughout the creep process and the mathematical relationships between it and the geometric parameters, internal pressures, creep crack incubation time were established through nonlinear regression. Finally, the proposed assessment function for creep crack incubation time was deduced from the above functions.