| This thesis investigates the dynamical behavior of spinning and/or axially moving beams.;The axially moving beams may represent appendages in the process of deployment (retrieval) from (into) a spacecraft or a prismatic joint in a flexible manipulator. It is shown analytically that when the length L changes, the transverse vibrations vary, in general, as L;An analysis of the effect of appendage root offsets (distance between the mounting point and system center of mass) on the dynamics of constant length spinning appendages is carried out. The stability and response characteristics of the system configuration are investigated taking into account the role played by the non-linear axial shortening effect, when the system is undergoing a steady spin, spin-up or angular slew maneuvers. It is observed that due to the root offset, large static deflections of the beams may result during steady spin of the system. Stability of elastic oscillations around non-trivial steady state configuration is examined and it is seen that, the axial shortening effect increases the stiffness during rotation. A positive offset along the beam causes similar effects on the stiffness matrix increasing the natural frequencies of vibrations. On the other hand, angular acceleration has a destabilizing effect. This destabilizing effect vanishes in the absence of offsets and is greater for larger offset. At some critical value of angular acceleration the frequency becomes zero for a given offset; beyond that the appendage buckles. Also the stability regions in the spin rate-spin acceleration plane are obtained. |
