Optimized representation for overlapped welded components using shell FE along with the structural stress method

The structural stress method is widely applied to fatigue analysis of welded components. The literature contains several modeling techniques capable of representing such structures. However, these techniques can only approximate the stiffness of the structure. The scope of the present work is to propose an optimization-based modeling technique to represent overlapped welded components (lap joints). This technique employs optimal parameters in order to reproduce the stiffness of the real structure without any significant errors. The design variable is defined as the thickness of the shell finite element representing the weld fillet. Linear programming is employed to solve the optimization problem. The objective function is defined as the residual error of the first natural frequencies obtained by a shell finite element model compared with the ones obtained by a solid model. This kind of modeling technique could be directly applied to large/complex problems, where global/local analysis are performed for structural integrity verification and fatigue life simulation. Once, this optimized modeling technique is used, global/local analysis are no longer needed and a single shell FE model can be applied for all the structural analysis. After proposing an optimization-based modeling technique, its result with respect to the structural stress are compared with the ones obtained with other methodologies presented in the literature and the standards. Results concerning errors when representing the structure total mass and first natural frequencies are presented.