Model Reduction and Dynamic Substructuring in Nonlinear Structures

One of the important challenges of industries that have large and complex products (e.g. wind turbines) is to build the most possible accurate full models of those large structures which could not be modeled or measured as a whole. In order to do so, a couple of theoretical and experimental aspects will be investigated in Substructuring approach which will be explained shortly

  • Interface dynamics of Substructures which includes a proper design of an intermediate connector (called transmission simulator) so that the extracted modes of the substrucrures project the real modes of them when coupled to the rest of the structure. In case there are some dominant nonlinearities (usually damping) in the interface that have major effects on the dynamics of the assembly, they also have to be identified and taken into account. For the case of reduction of the interface, the most important modes in the assembly have to be extracted. While the theory of substructuring with linear reduced model is well defined, substructuring with nonlinear reduced order models and interface reduction still need to be under consideration.
  • Hybrid coupling between Finite Element components and measured components, since it is an increasing requirement of industry. Such an approach allows a great flexibility in the constructions of models especially when some parts are too complex to be modeled or when some parts only exist as computer model and not yet as prototypes. No theory different from the current formulation is necessary, but specific issues need to be tackled. For instance how to couple components through interfaces that are, on the computational substructure side, having a full discretization with several hundreds of degree of freedom, and on the side of the experimental part, only a small number of measured points.
  • Test design which includes defining proper excitations and measurement point on different substructures to get all important data required in substructuring. Also important here is a proper use of highly precise and affordable acquisition systems (laservibrometer, 3D accelerometers, shaker, hammer, photogrammetry system,…) for different substructures to obtain accurate dynamic measurements with the least possible noise.

During the project, novel theories and methods will be applied empirically on the international benchmark consisting of a 600W Ampair wind Turbine, which is a first step to applying experimental substructuring on multi-megawatt turbines in the future.