Mechanical joint parameter estimation using frequency response functions and component mode synthesis

Abstract

This paper treats the problem of finite element model updating of structures consisting of substructures connected through mechanical joints whose stiffness and damping properties are unknown. The model is updated by estimating the mechanical joint parameters via the curve fit of measured frequency response functions using a non-linear least-squares method. A damped component mode synthesis formulation is used to calculate the theoretical frequency response functions of the assembled structure given the joint stiffness and damping parameter values. It is shown that a good approximation of the sensitivity matrix may be obtained by finite differences at a smaller computational cost than the closed form expression. Identifiability criteria and estimation errors are addressed. A numerical example consisting of two free-free beams connected through axial springs and dampers illustrates the proposed method.