A Complex Power Approach to Identify Joints in Experimental Dynamic Substructuring

The dynamic response of coupled structures is influenced by the mechanical joints connecting the individual substructures. The friction induced by the interfaces causes non-linear and dampinglike effects, which need to be taken into account when applying Experimental Dynamic Substructuring techniques. The traditional techniques impose compatibility of displacements at the interface between the substructures, enabling a rigid connection. This MSc. thesis proposes a compliant interface model in the framework of substructuring, in order to account for the influence of jointed connections. The proposed compliant interface model characterises non-linearities and damping effects of the interface connection as a function of the interface force and motion directly, rather than modelling it as a separate phenomenon. In fact, by making the interface force a function of a frequency dependent stiffness and damping term, all kind of interface behaviour can be modelled. As such the model fits into the Lagrange-Multiplier Frequency Based Substructuring method. In addition, the concept of complex power is adopted which allows to identify the dissipation levels being a function of the damping present in the structure. Also, it enables to isolate the contribution of the interface from the overall dissipation and characterises the effect of damping as such. The theory is illustrated with a test-case on a dedicated test structure. Interface stiffness parameters were identified based on a judgement of the resonance frequencies and mode shapes. Moreover, a successful attempt was made to identify interface damping parameters based on power dissipation of the structure.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin