Nonlinear Vibration Characteristics Of Laminated Thin-walled Cylindrical Shell

Due to the higher strength and simple structures, cylindrical shells, especially composite shell structures, now constitute a large percentage of industry engineering applications such as the casing of aircraft engine, drum-disk of gas turbine and airplane.The mechanical properties of cylindrical shell structure affects the performance of aircraft engine, gas turbine and aircraft, thus this type of shell structures were demand less probability of risk, and should maintain high structural integrity. However, compared with traditional boundary conditions, it can be found that there were little literatures about the vibration of shell with arbitrary boundary condition, let alone for the laminated composite shell structures. In present engineer fields, composite shell structures now constitute a large percentage of industry engineering applications, it is therefore of a great importance to carry out several investigations on the dynamical characters of laminated composite shells, especially the shells with complex boundary conditions, aiming to allow the engineers to avoid possible structure damage due to resonances or harmonic excitations.In present dissertation, with the support of Natural Science Foundation of China (NSFC), the vibration characteristic and response of the laminated shells were deeply investigated via the analysis method, experimental method and finite element method. The main achievements are listed as following:The Donnel’s thin shell theory and the composite structure homogenization theory were imported for the vibration analysis of composite casing and drum structures. By employing a set of orthogonal polynomials as the admissible function and the equivalent elastic constraint on cylinder edges which can be used to simulate the arbitrary boundary conditions, the equations of motion of the composite cylindrical shells with elastic boundary conditions was drived. Compared with the literatures’results, the present method is convenient and efficient to deal with vibration analysis of laminated composite cylindrical shells under arbitrary boundary conditions with acceptable accuracy. According to this method, several typical examples have shown some significant and interesting dynamic features of the symmetrically laminated composite cylindrical shells. The influence of different elastically boundary spring components can be easily distinguished when the vibration mode changed.The vibration performance of the laminated cylindrical shell with constrained layer damping treatment under arbitrary boundary conditions have been developed and investigated by using an improved Rayleigh-Ritz method. After defining the damping characteristic and calculation model of the constrained layer damping material, the analysis model of the constrain layer damping shell with elastic edges was established, in which the relationship of the basic layer, damping layer and constrain layer was considered. It is confirmed that the present method is accurate and convenient so that it is applicable to the thin laminated viscoelastic damping shell via comparing with the results of model experiment and ANSYS. The influence of different circumferential wave number and boundaries, especially the elastic supports, on the vibration character and model loss factor was calculated. A new dynamic model of a rotating shell with nonlinear rub-impact is established based on disk-drum system. Compared with the experimental results and finite element method, the present method is improved convenient and efficient to deal with vibration analysis of rotating shells with acceptable accuracy. Then, the effects of different impact-contact stiffness of the shell-stator contact, rotating speeds on the response of the shells were compared. The results indicated that due to the nonlinear characteristic of the rub-force, the vibration model of the shell can be inspired. Finally, the response of the laminated viscoelastic damping shell under nonlinear rub-force was analyzed.According to present investigation, the modeling theory of the laminated cylindrical shells with elastic boundary and nonlinear rubbing force was improved. The influence of different elastically boundary springs and lamination schemes was defined. Furthermore, these features may serve as efficient guidance for design of laminated cylindrical shells.