FEA shell element model for enhanced structural stress analysis of seam welds

摘要

The innovative approach consists of a new finite shell element model for the weld strength assessment, even for weld root fatigue of fillet welds. For fatigue, the enhanced structural stress is calculated using nodal forces and moments. The shell element model has been verified by comparing the stiffness and stress result with a refined solid element model. Weld root fatigue test results validate the model when the crack initiation direction is in the continuation of the nonfused root faces. In some cases, the Fricke structural stress method is not applicable, and evolvements are proposed. First, an analytic formula gives the critical weld throat section where the structural stress is maximum. The second proposal is related to the joints where both the weld itself and the attached flange plate are loaded at the root side. The stress distribution is bi-axial, and the two structural stress components are combined. Additional tests allow a structural stress design curve proposal for weld root fatigue with aluminium. In CAD tool, the FEA model preparation steps are described. First, a solid body feature of the weld is built. The industrial application of the model is demonstrated with a car-carrier trailer and a railway freight wagon.