Performance of a flexoelectric actuator for lamb wave excitation

A flexoelectric actuator represents a new approach for exciting Lamb waves in plate structures and, thus, can be potentially used for active structural health monitoring systems and microsensors. This paper analytically investigated the performance of a flexoelectric actuator for Lamb wave excitation. The constitutive equation for a thin plate flexoelectric structure was derived using the thermodynamics theory. A significant size effect could be demonstrated by the constitutive equation, which suggests a greatly enhanced curvature excitation performance at a small dimension. The interaction between the ideally bonded flexoelectric actuator with the plate could be simplified into two pairs of pin force and pin moment under the assumption of a weak coupling condition. The strain and the displacement responses to the pin-force and pin-moment pairs were obtained using the integral transform techniques and residue calculus. The pin-moment component mainly yielded an antisymmetric Lamb wave mode, while the pin force was reminiscent of its piezoelectric counterpart. The tuning of either a symmetric or an antisymmetric mode could be achieved by choosing an appropriate excitation frequency. The response under a five-cycle Hanning-window toneburst excitation signal was compared with the finite element analysis results and good agreement between them was found.