Nonlinear Magnetostriction
The Nonlinear Magnetostriction multiphysics node () passes the appropriate magnetization contribution from the Linear Elastic Material node in the Solid Mechanics interface to the Ampère’s Law, Nonlinear Magnetostrictive node in the Magnetic Fields interface. It also passes the inelastic strain contribution due to the applied magnetic field back to the Linear Elastic Material node. The strains are quadratic in terms of the material magnetization.
Instead of Magnetic Fields interface, you can also use Rotating Machinery, Magnetic interface.
Settings
The Label is the multiphysics coupling feature name. The default Label (for the first multiphysics coupling feature in the model) is Nonlinear Magnetostriction 1.
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 pzm1.
Coupled Interfaces
This section defines the physics involved in the Nonlinear Magnetostriction multiphysics coupling. The Solid mechanics and Magnetic fields lists include all applicable physics interfaces.
The default values depend on how the Nonlinear Magnetostriction node is created.
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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.
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If it is added automatically when The Nonlinear Magnetostriction Interface is selected in the Model Wizard or Add Physics window, then the participating Solid Mechanics and Magnetic Fields interfaces are selected.
You can also select None from either list to uncouple the Nonlinear Magnetostriction node from a physics interface. If the physics interface is removed from the Model Builder, for example Solid Mechanics is deleted, then the 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 interface. See Multiphysics Modeling Workflow in the COMSOL Multiphysics Reference Manual.
Domain Selection
The domain selection includes by default all applicable domains. Such domains represent an intersection of the applicable domains under the corresponding Magnetic Fields and Solid Mechanics interfaces selected in the coupling feature.
In Magnetic Fields interface, the following domain feature is applicable:
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Ampère’s Law, Nonlinear Magnetostrictive
In Solid Mechanics interface, the following domain material feature are applicable:
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Linear Elastic Material
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Hyperelastic Material (with the Nonlinear Structural Materials Module).
For nonsolid magnetic domains, remove them from the Solid Mechanics interface selection but keep them selected in the Magnetic Fields interface selection.
Coupling Type
From the list, choose one of these coupling types:
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 Fully coupled (the default) to include both the direct and inverse magnetostrictive effects.
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 Joule effect, also known as direct magnetostrictive effect, to include only the deformation of the material caused by its magnetization in response to the applied magnetic field.
 Villari effect, also known as inverse magnetostrictive effect, to include only the change in the material magnetization as a result of applied mechanical stress or strain.
Magnetostriction
From the Magnetostriction model drop down menu, choose one of the following options:
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 Isotropic (default)
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 Cubic crystal
For Isotropic choice, you can enter one dimensionless value of the Saturation magnetostriction, λs.
For Cubic crystal choice, you can enter two dimensionless values of the Magnetostriction constants, λ100 and λ111 corresponding to different crystallographic planes.
In both cases, the default is to take the values From material. Also enter the magnitude of the Saturation magnetization, Ms.
When this coupling node is used as a part of The Nonlinear Magnetostriction Interface multiphysics interface, the Ampère’s Law, Nonlinear Magnetostrictive feature under the corresponding Magnetic Fields interface also contains an input for the saturation magnetization. That input will then become inaccessible (grayed out), and the value entered at this coupling node will be used in all computations.
Advanced settings
To display this section, click the Show More Options button () and select Advanced Physics Option in the Show More Options dialog box.
You can select how the structural contribution due to the magnetostriction is accounted for. Two options are the Inelastic contribution to: Stress (default) or Strain.
This setting is effective only when the coupling type is set to either Joule effect or fully coupled. In the case of the contribution to stress, you can select which deviatoric stress will contribute to the effective field. The options are: Include elastic stress (default) or Include total stress.
The second option was the default behavior for the magnetostriction in COMSOL versions prior to 6.1.