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Permanent Magnet with Coin

Permanent Magnet with Coin

In this example a permanent magnet with a coin in front is to be created. Since this is geometry is symmetric in the and the plane, only 1/4 of the geometry is created. The magnet itself is composed of two regions, one which has a magnetization and the second part that is made of iron.

Load the OpenCascade and finite element packages:

First, a face of the magnet is created in the plane and then swept along a curve to obtain a solid component of the entire magnet region.

Create the sweep path:
Create the surface:
Create the OpenCascade shapes and the sweep:
Visualize the solid:

Next, the magnet is divided into the part that will later have a magnetization and the remainder of it.

Create a face the divides the magnet geometry:
Create the division:

The division will be used later. In the mean time, a coin is to be placed in front of the magnet. The geometry of this coin is also 1/4 of the full coin.

Create a 2D coin graphics primitive:
Convert the 2D coin to an OpenCascade shape:
Visualize the coin and the magnet:
Create a surrounding volume:
Create the OpenCascade shape of the surrounding volume:

In the next step all components are united to make the geometric model.

Extract the faces of all shapes:
Create the union of all faces:
Create the boundary ElementMesh:
Visualize the boundary mesh:

The geometric model contains a 1/4 geometry of a horseshoe permanent magnet, a coin in front of it and a bounding box. The reduction to the 1/4 geometry is possible due to the symmetries that the geometry has. One plane of symmetry is the plane and the second plane of symmetry is the plane. For the actual computation, only the 1/4 geometry will be used, but it is possible to visualize the full geometry.

Create the three remaining 1/4 geometries to create the complete geometry:
Visualize the complete geometry:

The geometry includes two iron regions: one in the horseshoe magnet and the other in the coin. The actual magnet region is located at the tip of the horseshoe magnet, and the surrounding domain consists of air.

One thing to keep in mind is the scale used in the geometric model. If the length of the boundary mesh is, for example, in units of meters, then the material parameters will need to be specified in consistent units. In this specific case, the units of the boundary mesh are in meters.

Mesh Generation

To perform a finite element analysis, the boundary mesh representation of the geometric model needs to be discretized into a mesh. In this same process, different material regions are specified with element markers.

Specify region markers:

Each material region integer marker is related to an arbitrary coordinate in that region.

Generate the mesh:
Visualize the parts specified by the markers:
Visualize the coin, magnet and iron regions:

More information about the mesh generation process can be found in the ElementMesh generation tutorial.