Effect of Increasing Piezomodules of the Initially Compressed Flexible Bimorph

The object of the study is flexible piezoelectric bimorphs of rod and membrane types, consisting of two or more homogeneous piezoelectric layers (films) of equal thickness with the same or opposite-directional polarization, interlayer, and external electrodes (are electrode coatings). The solution of the actual problem has been considered: increasing the operating characteristics of flexible piezoelectric bimorphs for more efficient use as generators of electric energy, sensors, and actuators—converters of control electrical signals into movement of working surfaces for manipulating or assembling microscale objects. The regularities of the influence of the magnitude of the initial longitudinal load applied to the ends of a bimorphic rod or uniformly distributed along the outer circular contour (perimeter) of the bimorphic round membrane on the resulting performance values for flexible piezoelectric bimorphs of the rod and membrane types, respectively, have been investigated. We believe that the magnitude of the longitudinal force applied to the movable end of the rod bimorph or to the outer perimeter of the membrane does not change over time and does not exceed the corresponding value of the strength of instability considering the cantilever or hinge fastening of the bimorph. Therefore, we have variable multidirectional bending directions of the bimorph (actuator) when an alternating control electric voltage is applied to the electrodes, i.e., when the sign of the control electric voltage is changed, the direction of bending (blocking force) also changes to the opposite one and after “switching off” the control electric voltage, the bimorph returns from the curved state to the original rectilinear one. Analytical solutions have been obtained for the deformation fields: deflections and angles of rotation of working cross sections of flexible piezoelectric bimorphs using the well-known “hypothesis of flat sections” and the method of Mor’s integrals in Mechanics of Materials. The effect of increasing the resulting deflections and blocking forces of flexible piezoelectric bimorphs because of the action of the initial compressive load has been identified and studied. The results of numerical modeling have been obtained for a flexible rod bimorph made of PZT piezoceramic layers, the effective deformation characteristics of which were determined by solving the reverse problem on the basis of the results of other authors. The cases of cantilever and hinge fastening of the ends of the rod bimorph have been considered. It has been found that the magnitude of the blocking force for the bimorph in the form of a hinged rod significantly exceeds that for the bimorph in the form of a cantilever, while the action of the longitudinal compressive force linearly increases the magnitude of the deflection and blocking force of the bimorph.