Abstract
Fatigue strength for root failure in fillet weld joints is conventionally estimated with nominal stress in weld throat. This idea is applicable only when the nominal throat stress is clearly obtained. This paper presents a new fatigue strength evaluation method for root failure, based on displacement at unfused zone around weld root. An advantage of the use of the displacement, instead of stresses, is low sensitivity to finite element mesh in FEA. We propose a method to use the displacement at the spot 1mm away from the root on unfused zone surface, obtained by FEA with 1mm size elements, as a parameter for fatigue strength evaluation. The results of analytical and experimental verification on load-carrying cruciform joints, butt joints and out-of-plane gusset joints demonstrate that the displacement based method can evaluate the fatigue strength of root failure with the accuracy equivalent to that of throat stress method.
