Electromechanical Forces
Use an Electromechanical Forces () coupling to model electromechanical interaction between deformable solids and electric fields, particularly in case when the deformations of the structure can significantly affect the electric field distribution.
The presence of such multiphysics node in the model will enforce the Include geometric nonlinearity option on all applicable study nodes.
Settings
The Label is the default multiphysics coupling feature name.
The Name is used primarily as a scope prefix for variables defined by the coupling node. Refer to such variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different coupling nodes or physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first multiphysics coupling feature in the model) is eme1.
Domain Selection
The domain selection is locked, so that all applicable domains are selected automatically. Such domains represent an intersection of the applicable domains under the corresponding Electrostatics and Solid Mechanics interfaces selected in the coupling feature.
In Electrostatics interface, the following two domains are applicable:
•
 Charge Conservation, if its material type input is set to Solid. Use this domain feature for solid dielectric materials.
•
 Charge Conservation, Ferroelectric
•
 Terminal. You can use the domain terminal feature to represent conductive solid materials such as, for example, doped silicon.
In Solid Mechanics interface, the following domain material feature are applicable:
•
 Linear Elastic Material
•
 Nonlinear Elastic Material (with the Nonlinear Structural Materials Module)
•
 Hyperelastic Material (with the Nonlinear Structural Materials Module).
For nonsolid dielectric domains, remove them from the Solid Mechanics interface selection but keep them selected in the Electrostatics interface selection.
electromagnetic stress
To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box.
Here, you can select the Electromagnetic Stress Tensor to be used in the coupling. The following options are available:
•
 Minkowsky (default)
•
 Einstein-Laub
•
 Chu
See About different stress forms chapter for more details.
Coupled interfaces
This section defines the physics interfaces involved in this Electromechanical Forces coupling. The Solid mechanics and Electrostatics lists include all applicable physics interfaces.
The default values depend on how the node is created.
•
If it is added from the Physics ribbon (Windows users), Physics contextual toolbar (macOS and Linux users), or context menu (all users), then the first physics interface of each type in the component is selected as the default.
•
If it is added automatically when the physics interface is chosen in the Model Wizard or Add Physics window, then the two participating physics interfaces are selected.
You can also select None from either list to uncouple the coupling from a physics interface. If the physics interface is removed from the Model Builder, for example Solid Mechanics is deleted, then the Solid mechanics list defaults to None as there is nothing to couple to.
If a physics interface is deleted and then added to the model again, then in order to reestablish the coupling, you need to choose the physics interface again from the lists. This is applicable to all multiphysics coupling nodes that would normally default to the once present physics interface. See Multiphysics Modeling Workflow in the COMSOL Multiphysics Reference Manual.