Post-Processing Surface Data Manipulation Capability
Recently, I have been learning to use the optimization tool Got-It, which comes with a built-in actuator example. While studying this example, I remembered a question that I discussed with Dr. Zhang from Tianyuan Technology Support a few days ago:
As shown in the figure below, there are two magnetic excitation sources in a static magnetic field space, with a ferromagnetic material (e.g., steel) in between. As is well known, in this static field, the ferromagnetic material will be magnetized, producing the magnetic field shown in the diagram. At this point, the properties of the material are similar to those of a permanent magnet, and it will be attracted by the two inherent magnetic sources. In finite element analysis, the resultant force acting on the object can be determined. However, how can we solve for the forces exerted by the two magnets separately?
Obviously, it is not accurate to build separate models for the left and right parts because the magnetization state in the ferromagnetic region, as shown in the figure below, is formed under the excitation of the composite magnetic field.
**Figure 1: Problem Description**
So, how should this problem be considered? A straightforward and effective approach is to treat the ferromagnetic material, after being magnetized by the composite magnetic field, as a permanent magnet excitation source. Then, separate models can be built for it and the two inherent magnetic excitation sources to calculate the force on the iron block in each model. This is a relatively challenging task for finite element software, as you need to not only fix the magnetic permeability of the ferromagnetic region but also fix the surface magnetic flux density vector distribution. This requires extremely stringent finite element data processing capabilities, and as far as I know, few software programs can achieve this (Ansoft can only fix the magnetization state of permanent magnets, but for ferromagnetic materials, it can only fix the permeability).
However, after studying FLUX’s material settings, we found that in the post-processing stage, not only can we fix the permeability, as Dr. Li mentioned in his video, but we can also fix some other electromagnetic field quantities (e.g., B, H, J, etc.) and assign them to the material properties. Here’s a step-by-step introduction to the specific operation method:
First, create a static magnetic field finite element model as shown in the figure below. On both sides are SN and NS permanent magnets with the same material, but with different distances from the central ferromagnetic region, so the resultant force on the iron core is not zero.
**Figure 2: Finite Element Model**
Solving this project yields the spatial magnetic field lines and the magnetic vector B distribution in the ferromagnetic region as follows:
**Figure 3: Spatial Magnetic Field Line Distribution**
**Figure 4: Magnetic Vector Distribution in the Iron Core Region**
Using computation, the resultant force on the iron core region is found to be FX = 4.65 N.
Next, we will introduce how to solve for the component force exerted by each permanent magnet on the iron core.
First, export the relative permeability of the ferromagnetic region and the magnetic flux distribution of the iron core region obtained from the above model analysis into a .dex file (this method can be found in the new FLUX self-study manual or Dr. Li’s video tutorial on “Inductance Calculation”).
**Figure 5: Fixed Magnetization State of the Iron Core Region**
Delete the solution results and save the new project separately.
**Figure 6: Save Project Separately**
Next, solve for the attraction of mag_1 on the iron core region. At this point, change the surface domain properties of mag_2 to air.
**Figure 7: Change Surface Domain Properties**
Import the magnetization data saved earlier into the new project in the form of a New tabulated spatial quantity.
**Figure 8: Import Magnetization Data**
Create a new quasi-permanent magnet material representing the magnetized ferromagnetic material, with the material type as Spatial linear magnet and the remanent magnetization and relative permeability as the surface data imported earlier.
**Figure 9: Create New Permanent Magnet Material**
**Figure 10: Assign New Material to Original Ferromagnetic Region**
After setting, click solve for calculation. The results are as shown below:
**Figure 11: Magnetic Field Established by mag_1 and Magnetized Iron Core**
**Figure 12: Magnetic Field Established by mag_1 and Magnetized Iron Core in Ferromagnetic Region**
**Figure 13: Frozen Magnetic Permeability in Ferromagnetic Region**
**Figure 14: Attraction of mag_1 on Ferromagnetic Region**
Therefore, the attraction of mag_1 on the ferromagnetic region is F1 = -11.07 N. Similarly, the attraction of mag_2 on the ferromagnetic region can be calculated, with results as follows:
**Figure 15: Magnetic Field Established by mag_2 and Magnetized Iron Core**
**Figure 16: Magnetic Field Established by mag_2 and Magnetized Iron Core in Ferromagnetic Region**
**Figure 17: Frozen Magnetic Permeability in Ferromagnetic Region**
**Figure 18: Attraction of mag_2 on Ferromagnetic Region**
Thus, the attraction of mag_2 on the ferromagnetic region is F2 = 6.41 N. The resultant force FX = F1 + F2 = -11.07 + 6.41 = -4.66 N, which is consistent with the resultant force FX = -4.65 N obtained in the first step.
