This paper contains an example of the transmission simulator method for experimental dynamic substructuring using the Ampair 600Wind Turbine. The structure of interest is the hub-and-three-bladed assembly. A single blade and hub is used as a substructure to develop a model for the hub-and-three-bladed assembly. The single-blade-and-hub substructure was developed from elastic modes of a free-free test and rigid body modes analytically derived from measured mass properties. This substructure can be rotated and replicated using the hub as a transmission simulator. Substructuring calculations were then performed using the transmission simulator method to derive a model of the hub-and-three-bladed assembly. This paper concludes with a comparison for this combined model to truth data derived from a free-free modal test of the entire rotor.
Developing constitutive models of the physics in mechanical joints is currently stymied by inability to measure forces and displacements within the joint. The current state of the art estimates whole joint stiffness and energy loss per cycle from external measured force input and one or two acceleration responses. To validate constitutive models beyond this state requires a measurement of the distributed forces and displacements at the joint interface. Unfortunately, introducing measurement devices at the interface completely disrupts the desired physics. A feasibility study is presented for a non-intrusive method of solving for the interface dynamic forces from an inverse problem using full field measured responses. The responses come from the viewable surface of a beam. The noise levels associated with digital image correlation and continuous scanning laser Doppler velocimetry are evaluated from typical beam experiments. Two inverse problems are simulated. One utilizes the extended Sum of Weighted Accelerations Technique (SWAT). The second is a new approach dubbed the method of truncated orthogonal forces. These methods are much more robust if the contact patch geometry is well identified. Various approaches to identifying the contact patch are investigated, including ion marker tracking, Prussian blue and ultrasonic measurements. A typical experiment is conceived for a beam which has a lap joint at one end with a single bolt connecting it to another identical beam. In a virtual test using the beam finite element analysis, it appears that the SWAT inverse method requires evaluation of too many coefficients to adequately identify the force distribution to be viable. However, the method of truncated orthogonal forces appears viable with current digital image correlation (and probably other) imaging techniques.