An Implicit Fillet-Weld Element Formulation for Mesh-Insensitive Fatigue Evaluation of Complex Structures

Abstract

In fatigue evaluation of welded structures, explicit weld representations in finite element (FE) models are needed for reliably capturing stress or strain concentration behaviors at critical weld locations, for example, weld toe or weld root, in using widely accepted traction structural stress or extrapolation hot-spot stress methods. The laborious efforts needed for generating weld geometry have been a major challenge for fatigue evaluation of complex structures containing many welds. In this paper, we present a user-defined fillet-weld element formulation and its numerical implementation for computing traction mesh-insensitive structural stresses. The fillet-weld element is formulated by connecting several linear four-nodes Mindlin shell elements around weld region as a user-defined element. The resulting elements can be directly used with major commercial FE codes through an available user subroutine interface. A number of well-documented fillet-welded components are then used for validating the accuracy and robustness of the developed fillet-weld elements.