Model Updating of Complex Assembly Structures Based on Substructures-Joint Parameters

To study the dynamic behavior of complex assembled structures consisting of several substructures and real joints connecting them, an updated finite element model of the associated structure is required. This paper presents a new technique to create an accurate updated finite element model of such structures. Given the fact that modal testing of real joints (such as bolt with some washers) are almost impossible; in this research the updated model of the assembled structures is constructed by utilizing parametric finite element model of the joint in conjunction with modal testing of the assembly structure and its substructures. In this paper, eigen-sensitivity method (used for characterizing cost function) and genetic algorithm (used for minimization scheme) are employed to update the assembled structure as well as substructures. A laboratory-scale unsymmetrical cross-beam is employed as the case study. The actual dynamic properties of the joint (including stiffness, mass and damping matrix) of this structure were estimated. The accuracy of the estimated parameters of the model was examined by comparison of the FRFs of the real assembled structure with the ones of the updated model. By achieving full compliance between these FRFs, the accuracy and efficiency of the proposed method, in a wide frequency range, is demonstrated.