Resonant modes of tubular shells and their use in ultrasonic linear motors

The association of two or more resonance modes of tubular shells on a new type of ultrasonic linear motor is discussed in this paper. Finite element analysis showed that tubular geometries provide several resonance modes with very close frequencies, indicating that axisymmetrical traveling waves could be generated as a composition of two or more them. Finite element method (FEM) simulations were employed to investigate resonance modes in tubular structures in a range of dimensions, and how strain distributes along the tubes in resonance. We found, for a tube with a length of 55mm long, and diameter 30mm, that excitation of 14^th and 15^th modes yields traveling waves with radial and longitudinal amplitudes of 2.8μm and 10.2μm respectively, when excited with two PZT rings driven with 35Vrms at 64.876kHz.