A Mechanics Based Parametric Description of Residual Stress Profiles for Fracture and Fatigue Assessment

It has been shown in a series of recent publications that any arbitrary residual stress distribution can be decomposited into through-wall “self-equlibrating” and “bending”. In this paper, a mechanics based parametric description of through-wall residual stress profiles is provided for fracture and fatigue assessment of girth welds. This parametric equation contains two fundamental parameters: (1) relative heat input and (2) pipe thickness to radius ratio. For a given welding procedure and heat input, the through-thickness resdual stress distributions as well as magnitude are shown to exhibit a continuous transition from bending to self-equilibrating as r/t ratio increases. As a result, a single parametric equation can be established for describing through-wall residual stress distributions for a full range of pipe diameters and thicknesses as well as weld configurations. A series of detailed finite element simulations were also performed to validate the predictions by the parametric equiations proposed.