Size dependent vibro-buckling of rotating beam based on modified couple stress theory

Micro-electro-mechanical and nano-electro-mechanical machines such as micro/nano pumps use a rotating beam as their energy transmission part. For such devices, dynamics behavior of a low scale tangentially loaded rotating beam is so important. Therefore, as the first step of each dynamical analysis, this paper concentrates on the free vibrations and stability of rotating micro/nano beams based on modified couple stress theory. For this purpose, equations of motion are obtained by combining Euler-Bernoulli and Timoshenko beam theories with modified couple stress theory and considering effects of tangential load and Coriolis force. Equations are two sets of coupled equations which are exactly solved. Validity and accuracy of the formulations are approved by comparing numerical results with literature. It is approved that there are three types of instability for rotating micro/nano tube which are strongly dependent to the modified couple stress theory's scale parameter, tangential load value and direction, and rotational speed. Finally, effects of geometrical and theoretical parameters on natural frequency and stability of rotating micro/nano tube are investigated and important outcomes are reported.