Résumé : The work presented in this thesis deals with experimental and theorical investigations corncerning the analysis and modification of the dynamic characteristics of structures. The effect of modification of the stiffness and damping are studied. Three methods are used to modify the dynamic response. In the first mathod, a soft foundation is replaced under the base of the rotor. The second introduces a soft material in the bearing. A damping material in the coupling between two sub-rotors is used as a third method. The curve fitting technique has been applied on the measured requency function for evaluating the dynamic parameters of the structure. A computer program is developed to solve the theoretical model, which combines the results of the finite element and the modal analysis techniques to calculate the dynamic parameters of the bearing. A simple physical model simulatng a rigid rotor on the soft foundation is investigated. The experimental work is carried on a laboratory model simulated a real on in an atomic station in France. The theoretical and the experimental results are in a good agreement. The previous three methods, which modifying the damping in the structures can be used to control the level ofthe vibration formthe structures
Notes : Thèse rédigée en anglais
Bibliogr. p. 146-153
Thèse de doctorat : Physique : Helwan University (Cairo) : 1992 (version d'origine)