Identification of Nonlinear Joint Characteristic in Dynamic Substructuring

Assembled structures often include local nonlinear behavior depending on the interface properties which can strongly change the overall dynamics. A typical example is a high local damping due to friction in bolted joints. A further example are bushing elements, like those which are widely-used in the automotive industry and which often show complicated characteristics like nonlinear stiffness and frequency dependency. In this contribution, measured and simulated FRFs of different systems are considered in order to identify nonlinear joint characteristics. The computation of the FRFs is established by the Harmonic Balance Method using a substructure formulation. A detection of the influence of the local damping properties is done by the Hilbert Transformation. For the computation of FRFs of systems with progressive stiffness, the Harmonic Balance Method is extended by a Continuation Method in order to be able to capture multiple solutions and is applied to a numerical example system. As an application an assembly consisting of two beam-like substructures coupled by a bolted joint is used in order to identify the friction characteristic of a real system. The results are used for further investigations of coupled axle parts of a wheel brake.