Toward Robust Response Models: Theoretical and Experimental Issues

The purpose of building a reliable response model requires awareness and understanding of the theoretical and practical problems and pitfalls that may be encountered along the process. Those issues have to deal with many different aspects of structural dynamics that will be tackled in this chapter. First of all, it is necessary to frame the problem in the context of structural dynamics and modal analysis; then, it is crucial to discuss the substructuring/coupling problem, especially when facing a very complex structure, which needs to be studied by parts. This leads us inevitably to the difficult task of measuring angular responses, that is, to measure the response at rotational degrees of freedom. A comprehensive discussion on this matter is given here. Not only due to the lack of information regarding rotational measurements, a constant issue is the incompleteness of the experimental data and its expansion to the numerical model size or the condensation/reduction of the numerical model to the experimental one. A significant discussion on this subject is also given in this chapter. Finally, the more recently developed transmissibility theory for N degrees of freedom allows for the estimation of unmeasured frequency response functions, contributing to the building of robust response models.