Two-parameter fracture characterization of a welded pipe in the presence of residual stresses

In this paper two-parameter fracture characterization of elastic and elastic-plastic stress/strain field around a crack front is presented for a welded pipe component containing a circumferential through-thickness crack. A macro function programmed in PYTHON is used to compute the constraint parameters (T-stress, Tz and Q factors) of the specimen in the open source finite element package Code_Aster. Data obtained from literature was employed to support three-dimensional finite element models developed in this research to study the impact of high magnitude repair-weld residual stresses. Complete distributions of the T-stress, Tz and Q-factors were obtained along a 3D crack front in the presence of residual stresses. The effects of stresses (residual and operational) on the constraint parameters are studied. It is shown that a two-parameter methodology provides effective characterization of three dimensional elastic-plastic crack tips constraint.