Performance of a flexoelectric actuator for lamb wave excitation

Abstract

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.

A flexoelectric actuator model with shear-lag and peel stress effects

“…For flexoelectric actuation, the only solution available in the literature is for the induced inplane shear force F and moment M induced at the actuator edges based on the pin-force-moment model. Their expressions are given by [59,60]…”

“…Wang et al [59] presented a consistent pin-force-moment model for a patch flexoelectric actuator rigidly bonded to a host beam considering the host structure compliance. Wei et al [60] employed this model to obtain an analytical solution for Lamb wave generation in plates using flexoelectric actuators. Ray [61] analysed a nanobeam integrated with a flexoelectric actuator layer using the FSDT, which, too, considered a rigid bonding at the actuator-beam interface.…”

“…The formulation is validated by comparing with the results of Luo & Tong [69] for the plane stress condition by considering only the piezoelectric effect. For the flexoelectric effect, the moment and force caused by the peel stress and shear stress, respectively, are compared with the pin-force-moment model [60] for a very stiff adhesive layer. Comprehensive numerical studies have been performed to demonstrate the effect of the plate, actuator and adhesive parameters on the interfacial stresses, plate deflection and curvature of the flexoelectric actuator.…”

The emancipation of flexoelectricity

“…The collection covers a wide variety of topics ranging from the application of flexoelectricity in flexible electronics, 41 sensing, 42 energy harvesting, 43,44 semiconductors, 45,46 to actuators utilized in structural health monitoring. 47 We also see the prospects of using flexoelectricity for mechanical reading of memory devices 3 and topics underpinning the theory of flexoelectricity. 48,49 An extensive and detailed overview of the mathematical and computational modeling of flexoelectricity is presented in Ref.…”

An electro-mechanical dynamic model for flexoelectric energy harvesters

“…Different from piezoelectricity which requires non-centrosymmetric constraint, flexoelectricity is a universal phenomenon that exists in all dielectrics including centrosymmetric materials. Flexoelectricity has a wide range of applications including nanodevices [28,29], sensors and actuators [29][30][31] and energy harvesters [32][33][34][35]. An energy harvester is a self-power autonomous electronic device operated by cultivating available existing power from the surrounding environment such as human movements, solar energy, and wind energy.…”