An exact solution for supercritical thermal configurations of axially moving Timoshenko beams with arbitrary boundary conditions is presented. The geometric nonlinearity and temperature variation of the traveling beams in supercritical regime is considered. Then, the nonlinear buckling problem is solved. A closed-form solution for the supercritical thermal configuration in terms of the axial speed,stiffness and thermal expansion is obtained.Some typical boundary conditions,such as fixed-fixed and pinnedpinned are discussed. More importantly, based on the exact solution,a new anti-symmetric thermal configuration for the fixedfixed axially moving Timoshenko beams is found.
The mechanism of a retracting cantilevered beam has been investigated by the invariant and energy-based analysis. The time-varying parameter partial differential equation governing the transverse vibrations of a beam with retracting motion is derived based on the momentum theorem.The assumed-mode method is used to truncate the governing partial differential equation into a set of ordinary differential equations(ODEs) with time-dependent coefficients. It is found that if the order of truncation is not less than the order of the initial conditions, the assumed-mode method can yield accurate results. The energy transfers among assumed modes are discussed during retraction. The total energy varying with time has been investigated by numerical and analytical methods,and the results have good agreement with each other. For the transverse vibrations of the axially retracting beam, the adiabatic invariant is derived by both the averaging method and the Bessel function method.
