4 Transmission Simulators & decoupling

Frequency Based Substructuring allows to directly couple separate component models. Combining models (in free-free condition) usually does not represent complex interface dynamics of the assembled system AB.

Some parts of the interface dynamics (friction/contact etc.) are challenging to model numerically. Therefore, we try to capture them experimentally in the component model using a Transmission Simulator (TS) that recreates the boundary conditions of the real assembly. An additional advantage of substitute coupling is to measure and/or excite the rotational and flexible modes at the interface of a subsystem that would otherwise not be accessible. A TS adds dynamical effects which are not part of the substructure (e.g., additional mass/stiffness). If they are relevant, they can be decoupled using Frequency Based Substructuring. An example of a TS design is depicted below:

Practical benefits of using Transmission Simulators:

• Consideration of unmodelled interface effects: interfaces may have minor yet non-negligible interface effects. To achieve a close characterization of these effects, the interface surfaces of the TS should have similar properties as the substituted component.
• Modal conditioning: if the structure is supplied with a TS with comparable mass and stiffness, one measures the structure in a much closer condition to the targeted assembly.
• Convenience of measurement: TSs allow for easier accessibility of the measurement equipment required to determine 6-DoF dynamics at the interfaces.
• Hybrid modeling: to receive a high-quality model, one could determine the FRF of the TS from a numerical model and decouple this from the experimental model of the assembly.