A finite element post-processor for fatigue assessment of welded structures based on the Master S-N curve method

The Master S-N curve method enables the use of computationally efficient coarse FE models without overlooking accuracy in fatigue life estimates of welded structures. However, the use of the method in daily design practice of engineering offices faces the barrier of a largely available finite element post-processor. This paper intends to fill the gap on how to implement a finite element structural stress post-processor for the Master S-N curve method in FEM software. Previous overlooked aspects of the Master S-N curve method in literature such as how to deal with solid and quadratic elements and how to smooth stress singularities with the Generalized virtual node method or using a rounded weld end are fully explained. Three demonstration examples of welded connections are illustrated and validated: (a) a uniaxial longitudinal welded attachment using linear/quadratic solid elements, (b) a flat plate subjected to high bending stresses and using a simplified representation of the weld end with quadratic shell elements, and (c) a welded tube subjected to multiaxial loading using shell and solid elements. The proposed algorithms show the full capabilities of the developed Structural Stress Post-processor for fatigue analysis of welded structures under constant amplitude loading and multiaxial stress states.