This tutorial is for COMSOL 5.3a
https://www.comsol.com/video/keynote-multiphysics-models-magnetostrictive-transducer-design
https://www.comsol.com/model/nonlinear-magnetostrictive-transducer-6063
Magnetostriction is an effect that causes a change in shape in all magnetic materials when they are exposed to a magnetic field.
magnetostrictive materials such as Terfenol-D and, more recently, Galfenol, which exhibit elongation as large as 0.04 to 0.2%.
The phenomenon of magnetic field induced strain is also known as the Direct (magnetostrictive) effect.
As a consequence of this bidirectional magnetomechanical coupling, we also see an Inverseeffect where stress acting on a magnetic material can change the magnetic state of the material itself by reorienting these tiny magnets. The Direct and Inverse effects are respectively used in actuation and sensing applications.
An air domain is created around the transducer to realistically model the magnetic flux path. The boundaries of this air domain are magnetically insulated which ensures that flux does not diverge out of the modeling domain. An alternate technique of implementing this air domain in COMSOL involves the use of Infinite Elements. For more information on Infinite Elements, please refer to the AC/DC Module User’s Guide
The implementation is straightforwards as you make use of a predefined multiphysics coupling interface available in COMSOL and called Magnetostriction. Selecting such interface in the model wizard will add Structural Mechanics and Magnetic Fields interfaces together with the corresponding multiphysics coupling feature Magnetostriction. Most of the settings you need to access in order to configure the coupling can be found under the Magnetostrictive Material feature added under the Structural Mechanics interface.
Modeling Instructions
From the File menu, choose New. NEW
In the New window, click Model Wizard.
MODEL WIZARD
1 In the Model Wizard window, click 2D Axisymmetric.
2 In the Select Physics tree, select Structural Mechanics>Magnetostriction.
3 Click Add.
4 In the Select Physics tree, select Structural Mechanics>Piezoelectric.
5 Click Add.
4 Click Study.
5 In the Select Study tree, select Preset Studies for Selected Physics Interfaces>Stationary. 6 Click Done
GEOMETRY 1
1 In the Model Builder window, under Component 1 (comp1) click Geometry 1.
2 In the Settings window for Geometry, locate the Units section.
3 From the Length unit list, choose mm.
Rectangle 1 (r1)
1 On the Geometry toolbar, click Primitives and choose Rectangle.
2 In the Settings window for Rectangle, locate the Size and Shape section.
3 In the Width text field, type 3.
4 In the Height text field, type 50.
5 Locate the Position section. In the z text field, type -25.
6 Right-click Rectangle 1 (r1) and choose Build Selected.
Union 1 (uni1)
1 On the Geometry toolbar, click Booleans and Partitions and choose Union.
2 Select the objects r3, r2, and copy2 only.
3 In the Settings window for Union, locate the Union section.
4 Clear the Keep interior boundaries check box
Point 1 (pt1)
1 On the Geometry toolbar, click Primitives and choose Point.
2 Click Build All Objects.
3 Click the Zoom Extents button on the Graphics toolbar.
GLOBAL DEFINITIONS
Parameters
1 In the Model Builder window, under Global Definitions click Parameters.
2 In the Settings window for Parameters, locate the Parameters section.
SOLID MECHANICS (SOLID)
1 In the Model Builder window, under Component 1 (comp1) click Solid Mechanics (solid).
2 In the Settings window for Solid Mechanics, locate the Domain Selection section.
3 Click Clear Selection.
4 Select Domain 3 only.
The solid mechanics equations will be solved only in the magnetostrictive material.
MAGNETIC FIELDS (MF)
On the Physics toolbar, click Solid Mechanics (solid) and choose Magnetic Fields (mf).
In the Model Builder window, under Component 1 (comp1) click Magnetic Fields (mf).
Ampère’s Law 2
1 On the Physics toolbar, click Domains and choose Ampère’s Law.
2 Select Domain 2 only.
3 In the Settings window for Ampère’s Law, locate the Material Type section.
4 From the Material type list, choose Solid.
5 Locate the Magnetic Field section. From the Constitutive relation list, choose BH curve.
SOLID MECHANICS (SOLID)
Magnetostrictive Material 1
1 In the Model Builder window, under Component 1 (comp1)>Solid Mechanics (solid) click Magnetostrictive Material 1.
2 In the Settings window for Magnetostrictive Material, click to collapse the Model input section.
3 Locate the Magnetoelastic Properties section. From the Magnetostriction model list, choose Nonlinear isotropic.
ADD MATERIAL
1 On the Home toolbar, click Add Material to open the Add Material window.
2 Go to the Add Material window.
3. In the tree, select Built-In>Air.
4 Click Add to Component in the window toolbar
MATERIALS
Air (mat1)
Select Domains 1 and 4–6 only.
ADD MATERIAL
1 Go to the Add Material window.
2 In the tree, select AC/DC>Soft Iron (without losses).
3 Click Add to Component in the window toolbar.
MATERIALS
Soft Iron (without losses) (mat2)
1 In the Settings window for Material, locate the Geometric Entity Selection section.
2 Click Paste Selection.
3 In the Paste Selection dialog box, type 2 in the Selection text field.
4 Click OK.
5 On the Home toolbar, click Add Material to close the Add Material window.
Material 3 (mat3)
1 In the Model Builder window, under Component 1 (comp1) right-click Materials and choose Blank Material.
2 In the Settings window for Material, type Magnetostrictive in the Label text field.
3 Select Domain 3 only.
4 Locate the Material Contents section. In the table, enter the following settings:
MAGNETIC FIELDS (MF)
In the Model Builder window, under Component 1 (comp1) click Magnetic Fields (mf).
Ampère’s Law, Magnetostrictive 1
1 In the Model Builder window, under Component 1 (comp1)>Magnetic Fields (mf) click Ampère’s Law, Magnetostrictive 1.
2 In the Settings window for Ampère’s Law, Magnetostrictive, locate the Domain Selection section.
3 From the Selection list, choose Manual.
4 Click Clear Selection.
5 Select Domain 3 only.