Magnetostrictive Material
The Magnetostrictive Material node defines the magnetostrictive material properties.
In case of linear magnetostriction model, the material data can be entered either in the strain-magnetization form using the elasticity matrix and the coupling matrix, or in stress-magnetization form using the compliance matrix and the coupling matrix. It is normally used as part of Magnetostriction multiphysics interface together with a Magnetostriction multiphysics coupling node and Ampère’s Law, Magnetostrictive node in the corresponding Magnetic Fields interface. Magnetostrictive Material node is added by default to the Solid Mechanics interface when adding a Magnetostriction multiphysics interface. The interface requires the AC/DC Module and at least one of the following modules: Structural Mechanics, MEMS, Acoustics.
When the Magnetostrictive Material node is added to the Structural Mechanics interface in the absence of an active Magnetostriction multiphysics coupling node, the material behaves similarly to a Linear Elastic Material node with some limitations on the format for the elastic material data input. All the magnetic material data and coupling data will have no effect. The magnetostrictive effect is then not included in the corresponding equation system.
By adding the following subnodes to the Magnetostrictive Material node you can incorporate other effects:
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Initial Stress and Strain
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Thermal Expansion (for Materials)
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Mechanical Damping
See also Magnetostrictive Material in the Structural Mechanics Theory chapter.
Linear Magnetostrictive Material Properties
Select a Constitutive relation — Strain-magnetization form or Stress-magnetization form. For each of the following, the default uses values From material. For User defined, enter other values in the matrix or field as needed.
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For Strain-magnetization form, select a Compliance matrix (ordering: xx, yy, zz, yz, xz, xy) (sH).
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For a Stress-magnetization form, select an Elasticity matrix (ordering: xx, yy, zz, yz, xz, xy) (cH).
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Select a Piezomagnetic coupling matrix (ordering: xx, yy, zz, yz, xz, xy) (dHT or eHS).
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Select a Relative permeability (μrT or μrS).
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Select a Density (p).
For entering these matrices, use the following order (Voigt notation), which is the common convention for magnetostrictive materials: xx, yy, zz, yz, xz, zy.
Density
If any material in the model has a temperature dependent mass density, and From material is selected, the Volume reference temperature list will appear in the Model Input section. As a default, the value of Tref is obtained from a Common model input. You can also select User defined to enter a value or expression for the reference temperature locally.
When using Common model input, you can see or modify the value of the volume reference temperature by clicking the Go To Source button (). This will move you to the Common Model Inputs node under Global Definitions in the Model Builder. The default value is room temperature; 293.15 K.
If you want to create a model input value which is local to your current selection, click the Create Model Input button . This will create a new Model Input node under Definitions in the current component, having the same selection as in the current node.
The density is needed for dynamic analysis or when the elastic data is given in terms of wave speed. It is also used when computing mass forces for gravitational or rotating frame loads, and when computing mass properties (Computing Mass Properties).
See also
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Mass Density and Volume Reference Temperature.
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Common Model Inputs and Model Input in the COMSOL Multiphysics Reference Guide.
Nonlinear Magnetostrictive Material Properties
See the corresponding the theory section Nonlinear Magnetostriction.
Geometric Nonlinearity
If a study step is geometrically nonlinear, the default behavior is to use a large strain formulation in all domains. There are, however, some cases when the use of a small strain formulation for a certain domain is needed. In those cases, select the Force linear strains check box. When selected, a small strain formulation is always used, independently of the setting in the study step. The check box is not selected by default to conserve the properties of the model.
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Magnetostriction
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Modeling Magnetostrictive Materials
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Modeling Geometric Nonlinearity
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Ampère’s Law, Magnetostrictive
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The Magnetic Fields Interface in the COMSOL Multiphysics Reference Manual
Location in User Interface
Context Menus
 Solid Mechanics>Material Models>Magnetostrictive Material
Ribbon
Physics tab with Solid Mechanics selected:
Domains>Material Models>Magnetostrictive Material