Jiashi Yang

Performance of a piezoelectric bimorph for scavenging vibration energy

We analyze the performance of a piezoelectric bimorph in the flexural mode for scavenging ambient vibration energy and evaluate the dependence of the performance upon the physical and geometrical parameters of the model bimorph. The analytical solution for the flexural motion of the piezoelectric bimorph shows that the output power density increases initially, reaches a maximum, and then decreases monotonically with increasing load impedance, which is normalized by a parameter that is a simple combination of the physical and geometrical parameters of the scavenging structure, the bimorph, and the frequency of the ambient vibration, underscoring the importance for the load circuit to have the impedance desirable by the scavenging structure. The numerical results illustrate the considerably enhanced performances achieved by adjusting the physical and geometrical parameters of the scavenging structure.

Connected Vibrating Piezoelectric Bimorph Beams as a Wide-band Piezoelectric Power Harvester:

We analyze coupled flexural vibration of two elastically and electrically connected piezoelectric beams near resonance for converting mechanical vibration energy to electrical energy. Each beam is a so-called piezoelectric bimorph with two layers of piezoelectrics. The 1D equations for bending of piezoelectric beams are used for a theoretical analysis. An exact analytical solution to the beam equations is obtained. Numerical results based on the solution show that the two resonances of individual beams can be tuned as close as desired by design when they are connected to yield a wide-band electrical output. Therefore, the structure can be used as a wide-band piezoelectric power harvester.We analyze coupled flexural vibration of two elastically and electrically connected piezoelectric beams near resonance for converting mechanical vibration energy to electrical energy. Each beam is a so-called piezoelectric bimorph with two layers of piezoelectrics. The 1D equations for bending of piezoelectric beams are used for a theoretical analysis. An exact analytical solution to the beam equations is obtained. Numerical results based on the solution show that the two resonances of individual beams can be tuned as close as desired by design when they are connected to yield a wide-band electrical output. Therefore, the structure can be used as a wide-band piezoelectric power harvester.

Transmitting electric energy through a metal wall by acoustic waves using piezoelectric transducers

The feasibility of transmitting electric energy through a metal wall by propagating acoustic waves using piezoelectric transducers is examined by studying the efficiency of power transmission and its dependence upon the relevant system parameters for a simplified system consisting of an elastic plate sandwiched by two piezoelectric layers. One of these layers models the driving transducer for generating acoustic wave, and the other layer models the receiving transducer for converting the acoustic energy into electric energy to power a load circuit. The output voltage, the output power, and the efficiency of this system are expressed as explicit functions of the system parameters. A numerical example is included to illustrate the dependence of the system performance upon the physical and geometrical parameters.

Analysis of piezoelectric devices

Three-Dimensional Theories Thickness-Shear Modes of Plate Resonators Slowly Varying Thickness-Shear Modes Mass Sensors Fluid Sensors Gyroscopes -- Frequency Effect Gyroscopes -- Charge Effect Acceleration Sensitivity Pressure Sensors Temperature Sensors Piezoelectric Generators Piezoelectric Transformers Power Transmission Through an Elastic Wall Acoustic Wave Amplifiers.

Piezoelectric waves near an imperfectly bonded interface between two half-spaces

We show the existence of certain waves propagating near an imperfectly bonded interface between two half-spaces of different piezoelectric ceramics. Some of the waves reduce to known waves when perfect bonding is assumed. There are also waves that rely on the imperfection of the interface bonding and they do not remain as interface waves when the bonding is perfect. In particular, it is shown that interface imperfection causes dispersion in general, although there does not explicitly exist a geometric characteristic length of the two-half-space structure. The theoretical results obtained can also be used to design experiments for measuring interface properties.

Thickness-shear vibration of rotated Y-cut quartz plates with relatively thick electrodes of unequal thickness

An exact solution is obtained from the three-dimensional equations of linear piezoelectricity for thickness-shear vibrations of rotated Y-cut quartz plates with relatively thick electrodes of unequal thickness at its major faces. Effects of the shear stiffness of the electrodes on resonant frequencies are examined.

Performance of a piezoelectric harvester in thickness-stretch mode of a plate

We studied mechanical-to-electrical power conversion of a piezoelectric plate driven mechanically into thickness-stretch vibrations. We have derived an analytical solution from the three-dimensional equations of linear piezoelectricity that shows the role of each of the physical parameters in determining the performance of such a piezoelectric device, usually measured by the output power density, the power efficiency, or both. Numerical results are included for illustrating the dependence of the device performance upon these physical parameters.

Harvesting magnetic energy using extensional vibration of laminated magnetoelectric plates

Magnetically forced extensional vibrations of laminated plates with piezoelectric and piezomagnetic layers are analyzed theoretically. It is shown that such a structure can be used to harvest magnetic energy and convert it to electric energy. The output power and the energy conversion efficiency are calculated. The load dependence of the magnetoelectric coupling coefficient is also obtained.

Nonlinear behavior of a piezoelectric power harvester near resonance

We analyze the behavior of a model piezoelectric power harvester near resonance. Nonlinear effects of large deformations due to resonance are considered using a cubic theory of the displacement gradient. Results on the output current and power are presented, which exhibit multivaluedness and jump phenomena.

Equations for thick elastic plates with partially electroded piezoelectric actuators and higher order electric fields

A system of two-dimensional equations for the flexural motion of an elastic plate with both electroded and unelectroded portions of piezoelectric actuators attached to the top and bottom surfaces are obtained. These equations include the extension and the bending effects of the piezoelectric actuators and the effects of rotatory inertia and shear deformations of the elastic plate. They are valid when the elastic plate is not thin and the actuators are not thin compared to the elastic plate. The equations also include the quadratic variation of the electric potential along the thickness of the actuators. It is shown that this quadratic electric potential variation is directly coupled to the flexure of the actuators and its effect is of the same order as the bending stiffness of the actuators which is usually small.