Creep constraint analysis and constraint parameter solutions for axial semi-elliptical surface cracks in pressurized pipes

• Creep constraints for axially cracked pipes with different crack sizes are analyzed.
• Solutions of the creep constraint parameter for cracked pipes have been obtained.
• Constraint levels of cracks in pipes increase with increasing crack depth and length.
• Constraint levels of all cracks in pipes are lower than that of standard CT specimen.
• Constraint effect needs to be considered in creep life assessment of the pipes.

Creep crack-tip constraints for axially cracked pipes with different geometries and sizes of semi-elliptical surface cracks have been analyzed by three-dimensional finite element method and the constraint parameter solutions were obtained. It has been shown that the constraint levels of cracks in the pipes increase with increasing crack depths and lengths. The constraint levels and creep crack growth rates of all cracks in the pipes are lower than those of the standard compact tensile specimens. Without considering the creep constraint effects, the excessive conservatism may be produced in creep life assessments of the axially cracked pipes.