Overview

Test Case

The TEAM 20 problem is a non-linear, magnetostatic, 3D model designed to verify magnetostatic force calculations. The center pole and yoke are made of steel. The coil is a source circuit with imposed ampere-turns. The model allows you to investigate surface magnetic force calculations obtained by the LS-DYNA monolithic solver in magnetostatic cases under different current excitations.

The goal is to determine flux densities at specific surface points within the model as well as the magnetostatic force for different values of ampere-turns. Results are then compared to experimental results in the reference.

Figure 201: Problem Sketch

Figure 202: Problem sketch and dimensions (in mm)

Figure 203: Problem setup

Analysis Assumptions and Modeling Notes

LS-DYNA *EM_CONTROL card is set to 1 to activate the Eddy Current solver.

The ampere-turns are specified using a load case within *EM_CIRCUIT_SOURCE. The &curr corresponds to the different values of current intensity for each timestep of the simulation. This way, it is possible to analyze different current intensities within the same simulation—that is, one simulation handles several static problems.

The current values as well as others are parametrized.

Finally, electromagnetic properties are given using EM_MAT_002 and EM_MAT_001.

The mesh is formed by solid elements formulation 1, which is a constant stress solid element.

Figure 204: Mesh

Results Comparison

The following results are extracted and compared against the experimental results:

The point of interest as well as α-β (center pole) and ϒ-δ (yoke) lines are shown in Figure 205.

Figure 205: Reference point and α-β (center pole) and ϒ-δ (yoke) lines

Point information is retrieved from em_pointout.dat file. Information for α-β as well as ϒ-δ is retrieved from em_rogoCoil_002.dat and em_rogoCoil_003.dat, respectively. Information provided in em_rogoCoil files are per area, which means that results must be divided by the cross area before comparing them to the experimental results.

Reference results are compared to the LS-DYNA output in Figure 206, Figure 207, Figure 208, and Figure 209. As you can see, there is a good correlation between them.

Figure 206: Simulation vs experiment results of Bz at point (0,0,25.75)

Figure 207: . Simulation vs experiment Bz flux for α-β area

Figure 208: . Simulation vs experiment Bz flux for ϒ-δ area

Figure 209: Simulation vs experiment for electromagnetic force

The error between the experimental results and the simulation at different ampere-turn values is presented in the bar charts below: Figure 210, Figure 211, Figure 212, and Figure 213. Errors remain below 4.5% except for point (0,0,25.75) at 1000 AT in Figure 210. This discrepancy is likely due to the difficulty of measuring this very narrow location during the experiment.

Figure 210: Relative error for Bz at point (0,0,25.75)

Figure 211: Bz relative error for alpha-beta line

Figure 212: Bz relative error for gamma-delta line

Figure 213: Electromagnetic force relative error