Dynamic torsion of laminar beams as a working principle for sensors

ABSTRACT: A method is presented in order to put planar structures in a pure torsion, bydirectly acting from their surfaces where a stress state is induced, taking advantage ofpiezoelectric layers that are integral with them. An experimental investigation was carriedout on alumina beams which, in a portion of their faces, support two ferroelectric layers ofPZT created using conventional thick-film technology processes. A suitable system ofcoplanar electrodes, embedded in the layers, promotes piezoelectric deformations parallel tothe substrate, induced by a voltage across them. At the layer-substrate interfaces,completely in-plane stresses are created and when they are conveniently oriented, the beamis prompted into pure torsion which takes on the characteristics of a vibration following theapplication of alternated voltage.Besides describing the design and realization of the sample beams, this work reports ontheir dynamic behaviour in torsion, the experimental set-ups and the procedures for itscharacterization. The results are discussed and highlighted in order to outline the potentialof the method with regard to using the realized beams as primary sensors for physicalquantities. To this end, proposals for possible