Unified constraint parameter solutions for axial and circumferential surface cracks in pressurized pipes under creep condition

Unified creep constraint parameter Ac for axial and circumferential surface cracks in pressurized pipes have been calculated and investigated by three-dimensional finite element method. It has been shown that the parameter Ac can effectively characterize in-plane and out-of-plane creep constraints in pressurized pipes. The overall constraint levels of pipe cracks increase with increasing crack depth, length, pipe wall thickness and radius-thickness ratio. The parameter Ac solutions have been obtained for different pipe geometries and crack sizes. In creep life assessments of pressurized pipes, the overall constraint effect can be incorporated by the unified constraint parameter Ac. For shallower and shorter surface cracks in pipes, more benefits can be gained by incorporating constraint effect.