In this work, the feasibility to perform substructuring technique with experimental data is demonstrated. This investigation examines two structures with different additional mass‑loads, i.e. transmission simulators (TSs). The two structures are a single blade and the hub together with two blades from an Ampair 600 wind turbine. Simulation data from finite element models of the TSs are numerically decoupled from each of the two structures. The resulting two structures are coupled to each other. The calculations are made exclusively in the frequency domain. A comparison between the predicted behavior from this assembled structure and measurements on the full hub with all three blades is carried out. The result is discouraging for the implemented method. It shows major problems, even though the measurements were performed in a laboratory environment.

In dynamic substructuring, a complex structure is divided into multiple substructures that can be analysed individually and these individual component responses are coupled together to obtain the global response of the whole structure. Dynamic substructuring can be performed on substructure models that are identified either experimentally or analytically. For dynamic substructuring to be successful, it is very essential to have the precise information of the connection points or the interfaces between the substructures. The method has been extensively used with analytical models in most of the available standard finite element software packages where the information about all degrees of freedom is known. However, it is difficult to get the information about all connection degrees of freedom from the measurements and experimental substructuring is thus limited in its use compared to analytical substructuring. In order to overcome these difficulties, the Transmission Simulator method commonly also known as Modal Constraints for Fixture and Subsystem method can be used. In this method, an additional fixture called Transmission Simulator which is available both physically and analytically, is attached to the substructures at the interfaces and their respective responses are measured. The substructures could be analytical as well as experimental. The coupling is done by constraining the transmission simulator on the substructures to have the same motion and the effect of the transmission simulator is later removed from the coupled structure by subtracting the analytical transmission simulator model. This method has been successfully implemented for Component Mode Synthesis and Frequency Based Substructuring for structures with multiple connection points at a single location. In this thesis work, frequency response function based experimental–analytical dynamic substructuring using the transmission simulator is performed on a rear subframe and rear differential unit assembly of a Volvo XC90 car where the differential unit is connected to the subframe at three locations. The aim of this work is to verify the Transmission Simulator Method for multiple location connection points using the frequency response functions and build confidence on the methodology in order to be used for future work at Volvo Car Corporation.

Dynamic Substructuring is a powerful tool for simplification of the analysis of complex structures and it has been well established along the years in analytical calculations by means of the Craig-Bampton technique. Recently, a new branch of substructuring, the Experimental Dynamic Substrucuring, appeared as a promising field of research for the engineering community. This area presents several intrinsic difficulties, evincing a need to develop the traditional substructuring methods towards obtaining better results using the experimental approach. In this scenery, the Transmission Simulator technique emerges as an instrument for potential improvement of the achieved results. This work represents a study on the use of the Transmission Simulator technique in the analysis of an Ampair A600 wind turbine blade subjected to loads at the interface to the hub, and it is a part of the benchmarking studies of SEM (Society of Experimental Mechanics). The work consisted of collecting experimental data via vibration tests of a single blade connected to different sizes of transmission simulators. After that, a mathematical representation of the blade was obtained via subtraction of the effect of the transmission simulators via substructuring technique. The computed model was subsequently coupled to a model of the remainder of the wind turbine (the hub plus two blades), and the results were compared to data acquired in tests of the whole assembly. The final findings did not reflect the theory prospects and further investigation is necessary to evaluate the effectiveness of the used methodology.