The Piezoelectric Devices Interface

) interface combines Solid Mechanics and Electrostatics together with the constitutive relationships required to model piezoelectrics. Both the direct and inverse piezoelectric effects can be modeled, and the piezoelectric coupling can be formulated using either the strain-charge or stress-charge forms.

When a predefined interface is added from the branch (

) of the or from windows, and interfaces are added to the Model Builder.

In addition, the node is added, which automatically includes the multiphysics coupling feature .

The participating interface includes the default feature with its selection set to all domains. The interface has a default feature with similar settings.

Such features can be also added manually to their corresponding interfaces similar to any other material model therein.

The multiphysics node Piezoelectric Effectcan be active only on the selection, where both features Piezoelectric Material and Charge Conservation, Piezoelectric are active.

You input both the mechanical and electrical material data under the Piezoelectric Material node. The data can be presented in either stress-charge or strain-charge form.

When it is used without an active Piezoelectric Effect coupling feature, the Piezoelectric Material node works similarly to a Linear Elastic Material feature with the material data input limited to anisotropic form using Voigt notations. All the electric material data has no effect.

You use the Charge Conservation, Piezoelectric feature under Electrostatics to select those domains, where the material is supposed to experience piezoelectric coupling. When used without a counterpart under the Solid Mechanics interface (and/or without the coupling feature) Charge Conservation, Piezoelectric node acts as an ordinary Charge Conservation feature with its material data input limited to the electric permittivity only.

All solid mechanics and electrostatics functionality for modeling is also accessible to include surrounding elastic solids or air domains. For example, add any solid mechanics material for other solid domain, a dielectric model for air (via Charge Conservation feature), or a combination. Note that in order to model a non-solid dielectric domain, you need to remove such domain from the domain selection for the entire Solid Mechanics interface. This is because all material models under that interface represent solid materials (with the Linear Elastic Material node being always present and active in all those domains, where it is not explicitly overridden by any other material model).

In 2D and 2D axial symmetry, adding a Piezoelectric Devices interface also adds predefined base-vector coordinate systems for the material’s (in the plane 2D case) XY-, YZ-, ZX-, YX-, XZ-, and XY-planes. These additional coordinate systems are useful for simplifying the material orientation for the piezoelectric material.

The Solid Mechanics interface is intended for general structural analysis of 3D, 2D, or axisymmetric bodies. In 2D, plane stress or plane strain assumptions can be used. The Solid Mechanics interface is based on solving Navier’s equations, and results such as displacements, stresses, and strains are computed.

The Electrostatics interface is used to compute the electric field, the electric displacement field and potential distributions in dielectrics under conditions where the electric charge distribution is explicitly prescribed. The formulation is stationary but for use together with other physics interfaces, also eigenfrequency, frequency-domain, small-signal analysis and time-domain modeling are supported in all space dimensions.

The physics interface solves Gauss’ law for the electric field using the scalar electric potential as the dependent variable.

	In previous versions of COMSOL Multiphysics, a specific physics interface called Piezoelectric Devices was added to the Model Builder. Now, a predefined multiphysics coupling approach is used, improving the flexibility and design options for your modeling. For specific details, see The Multiphysics Node and Multiphysics Modeling Approaches in the COMSOL Multiphysics Reference Manual.

When physics interfaces are added using the predefined couplings, for example , specific settings are included with the physics interfaces and the coupling features.

However, if physics interfaces are added one at a time, followed by the coupling features, these modified settings are not automatically included.

For example, if both and interfaces are added, COMSOL adds an empty node. You can choose the available coupling feature but the modified settings are not included.

	Coupling features are available from the context menu (right-click the Multiphysics node) or from the Physics toolbar, Multiphysics menu.

	Use the online help in COMSOL Multiphysics to locate and search all the documentation. All these links also work directly in COMSOL Multiphysics when using the Help system.

The Piezoelectric Effect coupling feature node is described in this section.

Additional nodes and subnodes available with this multiphysics interface are described with the interfaces where they are available. , , , and subnodes are available for Piezoelectric Material under the Solid Mechanics interface. The feature is described for the Electrostatics interface.