Dynamic Characteristics And Resonance Behavior Of A Spinning Composite Cylindrical Thin Shell

Dynamic characteristics and resonance behavior of a spinning composite cylindrical thin shell are investigated in this dissertation.Of great interest in this dissertation is the combined effects of spinning angular velocity,hygrothermal effects and disturbed amplitude on vibration characteristics,instability regions and frequency response curves.Based on Love’s shell theory,and introducing hygrothermal strains into the constitutive relation of composite cylindrical thin shell,two kinds of dynamical models of spinning composite cylindrical thin shells are built by means of Hamilton’s principle,and the accuracy and usability of the above two kinds of models are verified by means of previous models.Travelling wave vibration of a spinning composite cylindrical thin shell in hygrothermal environment is investigated.Specical attention is given to the influence of hygrothermal effects on travelling wave vibration characteristics of the shell.Effects of spinning angular velocity,air flow velocity,temperature,moisture,fiber orientation angle,boundary conditions on vibration characteristics of the system are discussed,and the influence of initial hoop tension generated by spinning motion on frequency parameters of forward and backward travelling waves and critical spinning angular velocity of the shell is also analyzed.The results reveal that coriolis force caused by the spinning motion induces the traveling waves effects,initial hoop tension is dominant factor leading to the disappearance of critical spinning velocity of the system,and spinning angular velocity,air flow velocity and hygrothermal effects show the significant influence on vibration characteristics of the shell.Parametric vibration of a functionally graded cylindrical thin shell with periodic spinning angular velocity in thermal environment is carried out using the multiple scales method,and the instability boundaries of the shell under the case of combination and primary parametric resonances are also given.Effects of temperature and power law index on the frequencies of forward and backward travelling waves of the shell are discussed,and the influence of constant spinning angular velocity,temperature,power law index and various boundary conditions on instability regions of combination and primary parametric resonances is dealt with.From the results it is seen that spinning velocity,temperature and power law index all broaden the instability regions.Parametric instability of a spinning functionally graded cylindrical thin shell subjected to both axial disturbance and thermal environment is studied,in which the axial disturbance is defined as periodic displacement excitation acting on the longitudinal direction of the shell.The partial differential equation is discretized into ordinary differential equations via the Galerkin method,the parametric instability is analyzed employing the multiple scales method,and the instability regions of the system under the case of combination parametric resonances are obtained.The influence of axial disturbed amplitude,spinning angular velocity,temperature,power law index and axial compressive loads on instability regions is researched systematically.The outcomes show that there is only combination instability region when axial disturbance is considered in the condition of linear vibration,and primary instability regions do not exist.An analytical solution of nonlinear parametric vibration of a spinning composite cylindrical thin shell subjected to time-dependent axial loads is presented by means of the Galerkin method and the multiple scales method,and the stability conditions of trivial and untrivial solutions are obtained using the Routh-Hurwitz criterion.The effects of initial axial load,the disturbed amplitude of axial load,spinning angular velocity,viscous damping coefficient,fiber orientation angle and hygrothermal environment on frequency response curves and instability regions of the system under the case of low-frequency and high-frequency parametric resonances are studied.Employing the multiple scales method,the analytical solution of nonlinear forced vibration of a spinning composite cylindrical thin shell under radial external excitation is derived,and stability conditions and bifurcation characteristics in the condition of low-frequency and high-frequency primary resonances are obtained.The influence of amplitude of external excitation,spinning angular velocity,fiber orientation angle,viscous damping coefficient and hygrothermal effects on frequency response curves of the system is analyzed.Finally,the research concent and the results of this work are summed up,and a brief plan for future studies is given.