The Magnetostriction () interface combines Solid Mechanics and Magnetic Fields together with the constitutive relationships required to model magnetostrictive materials and devices. Both the direct and inverse magnetostriction effects can be modeled.

When a predefined Magnetostriction interface is added from the Structural Mechanics branch () of the Model Wizard or from Add Physics windows, Solid Mechanics and Magnetic Fields interfaces are added to the Model Builder.

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

The participating Solid Mechanics interface includes the default Magnetostrictive Material feature with its selection set to all domains. The Magnetic Fields interface gets a default Ampère’s Law, Magnetostrictive feature with similar settings.

The multiphysics node Magnetostriction can be active only on the selection, where both features Magnetostrictive Material and Ampère’s Law, Magnetostrictive are active.

You input both the mechanical and magnetic material data under the Magnetostrictive Material, and the electrical properties under Ampère’s Law, Magnetostrictive.

You use the Ampere’s Law, Magnetostrictive feature under Magnetic Fields to select those domains, where the material is supposed to experience magnetostrictive coupling. When used without a counterpart under the Solid Mechanics interface (and/or without the coupling feature) Ampère’s Law, Magnetostrictive node acts as an ordinary Ampère’s Law feature with its material data input limited to the electric properties only. The magnetic permittivity of free space will be assumed.

All solid mechanics and magnetics 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 non-solid model for air (via Ampere’s Law feature), or a combination. Note that in order to model a non-solid magnetic material, 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 Magnetostriction 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 non isotropic magnetostrictive materials.

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

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

The Magnetostriction 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. Mechanical Damping and Thermal Expansion subnodes are available for Magnetostrictive Material under the Solid Mechanics interface. The Ampère’s Law, Magnetostrictive feature is described for the Magnetic Fields interface.