Passive Control and Local Structural Modification of a Mechanical System Through the Application of High Stiffness Double Layer Dampers

A study on a passive modal control to be applied to a generally constrained mechanical system is presented, able to cut down frequency peaks in a selective way. A preliminary modal analysis is needed in order to define the system eigenvalues and eigenvectors; then, Damping, Stiffness and Mass experimental matrices can be obtained. Starting from these data, the developed methodology allows to define a damping matrix able to modify the local and global structural modes. In order to validate the reliability of the theoretical model, a simple five degrees of freedom model was first examined, with known stiffness and mass matrices, and a solution for a chosen damping matrix was checked. Successively the same solution was verified giving the theoretical model incomplete information regarding the eigenvalues and eigenvectors matrices. Having validated the theoretical model on a simple system, the methodology was applied to a car roof, realizing a modal modification starting from partial information on the eigenvalues and eigenvectors matrices.