Identification of a nonlinear joint in an elastic structure using optimum equivalent linear frequency response function

Abstract

As the main source of local nonlinearities, joints can lead to drastic changes in dynamic behavior of structures in a global scale. Finite element (FE) models often lack these nonlinearities and are incapable of representing nonlinear behavior. Therefore, the identification of nonlinear dynamic mechanical properties of the joint is necessary, in order to develop a faithful FE model of the structure. In the present work, dynamic parameters of a nonlinear joint are identified using an optimum equivalent linear frequency response function of the structure. A test rig, which includes a beam that can produce cubic stiffness spring characteristic as a nonlinear joint, is built, and nonlinear dynamic characteristics of the beam are identified. In addition to hardening behavior related to cubic stiffness, softening effects were also observed in some measured modes in which further investigation attributed that behavior to the presence of a bolt in the test rig.

Nonlinear aeroelastic stability analysis of hingeless helicopter rotor blades using FRF coupling and condition number

“…In fact, OELF replaces HB for experimental studies where the said matrices are not available. Experimental implementation of this technique for identifying nonlinearity and its type and model has been successfully applied by Sadati and Nobari [14]. The procedure of deriving of aerodynamic FRF of Greenberg theory is presented in reference [9].…”

Nonlinear Modeling and Identification of an Aluminum Honeycomb Panel with Multiple Bolts

“…where 1 and 2 are length and width of the thin layer element and is the thickness of the thin layer element. To facilitate numerical computation, it is suggested by [31] to select ∈ [10,100]. In this work, the thickness of the thin layer is chosen such that = 100.…”

“…An accurate model for joints is the key to the success of the dynamic analysis of assembled structures. Many researchers have focused on how to resolve such a problem using the theoretical or experimental methods [7][8][9][10]. For instance, Kuether and Allen presented two model substructuring techniques for describing the nonlinear dynamic behavior of an assembled structure [11].…”

Study of surface bonding imperfection effects on equivalent identified dynamic Young’s and shear moduli using a modal based joint identification method

“…Because of a joint's role in connecting structures with different impedances at connection points, the joining medium is usually subjected to high level of strains and hence joint's dynamic mechanical properties can significantly affect dynamical response of the structure [11][12][13]. This effect can be used in reverse order to identify the bonding medium (here adhesive) mechanical properties.…”