Smoothing experimental data in dynamic substructuring of built up systems 3 Application The decoupling technique is tested on an experimental benchmark, chosen in order to be quite simple, at least theoretically, easy to modify, and free from problems due to rotational degrees of freedom. Therefore, a benchmark that can be modelled as a lumped parameter system is selected. The model is shown in Fig. 3: the coupled system are a 4 DoFs system and the two subsystems, denoted by letters A and B, have 3 DoFs. m1 m4 m5 m2 m3 m6 B A k 1 k 2 k 3 k 5 k 6 k 4 Fig. 3 Lumped model benchmark 3.1 Experimental benchmark A first version of the benchmark is shown in Fig. 4. It consists of 2 rail guides bolted on an horizontal table and eight guide carriages. Mass m1 consists of two rigidly connected guide carriages lying on different rails, as mass m4. Each lumped stiffness consists of two springs in parallel. However, sliding of the carriages within the guides proves to be quite difficult due to several problems, as for instance the fact that the rail guides are not perfectly parallel. Therefore a second version of the benchmark is built without using the guides. In this case the motion occurs along a vertical direction, as shown in Fig. 5. However, without the guides, small displacements orthogonal to the vertical direction may occur, as well as small rotations. 97
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