An efficient mode based approach for the dynamic analysis of jointed and locally damped structures: Joint interface modes

The mechanical behavior of complex elastic structures with substructures is significantly influenced by the local and nonlinear constitutive behavior of the involved joints [1]. Well-established computational techniques, which are mostly based on the direct finite element method (FEM) or on classical modal reduction procedures, show an inefficient balance between computational time and accuracy. Based on Joint Interface Modes (JIMs), which have been recently proposed by our group [2], it is possible to perform mode based dynamic computations of jointed elastic structures utilizing local and nonlinear contact and friction models. This approach is characterized by almost the same accuracy as the full FEM, without loosing the efficiency of modal computation. It is a well known effect that local damping couples the degrees of freedom (DOFs) in a mode based computation [3]. Typically, this effect is neglected in engineering praxis in order to preserve the computational efficiency of the modal approach. The present paper is devoted to demonstrate that the use of JIMs allows the consideration of the mode coupling due to damping. Our work is organized as follows: In the first section two numerical studies are performed in order to demonstrate the range of possible errors due to the common neglect of the coupling effect of local damping in a mode based analysis of jointed structures. In a second section the concept of 'Joint Interface Modes' is briefly reviewed and in the last section a numerical example utilizing JIMs is presented. Beside an excellent balance of accuracy and computational effort, it can be seen that the JIMs formulation enables full mode coupling due to local energy dissipation.