ANALYSIS OF RESIDUAL STRESSES IN PIPE SEAM WELDS AND A PROPOSED RESIDUAL STRESS PROFILE ESTIMATION METHOD

A recent comprehensive investigation into residual stress distributions in pipe and vessel longitudinal seam welds is presented in this paper, covering component wall thickness from 1/4 '' (6.35mm) to 10 '' (254mm), component radius to wall thickness ratio from 2 to 10, and linear welding heating input from low (50 J/mm) to high (6000 J/mm). Through the use of a residual stress decomposition technique, two key parameters that govern through-thickness residual stress distributions in terms of their membrane and bending content have been identified. One is component radius to wall thickness ratio (r/t) and the other is a characteristic heat input density ((Q) over cap) having a unit of J/mm(3). With these two parameters, a unified functional form for representing through-thickness residual stress profile behaviors in seam welds is proposed along with its solution procedure for applications in weld region. The simplicity of the proposed residual stress profile estimation scheme in functional form and demonstrated applicability for a wide range of r/t and (Q) over cap provides an effective framework for generating residual stress profile information for supporting defect assessment procedures in FFS codes and standards.