Importing mechanical stress distributions into Flux 2D

Introduction

As discussed in the page presenting the B(Stress) property, materials with a magneto-mechanical property may be assigned to laminated magnetic non conducting regions in Flux 2D. In these regions, the distribution of mechanical stress may be used to modify the constitutive relationship B(H) of their materials. This feature allows users to model magneto-mechanical effects resulting from mechanical constraints (e.g., centrifugal forces or residual stress related to manufacturing).

The mechanical stress distribution ruling this effect in a laminated region may be evaluated with dedicated structural mechanics software such as SimLab/OptiStruct and then be imported into a Flux project as a spatial quantity. This page describes how to import the mechanical stress distribution results issued from that software into Flux to create this dedicated spatial quantity.

Import distribution from SimLab/OptiStruct

To import a mechanical stress distribution into a Flux 2D project as a spatial quantity, two files issued from SimLab/OptiStruct are required as inputs, namely:
  • A mesh file (.fem extension) representing the support over which the stress distribution has been evaluated. Typically, this mesh is associated to the ferromagnetic parts of the device (e.g., the rotor or the stator of a machine) and corresponds to their discretization used in the structural mechanics simulation carried out with SimLab/OptiStruct.
  • A complementary data file (.txt extension) storing the stress values on the previous mesh. The stress values must be expressed as scalar values on nodes (typically the von Mises stress value) in MPa.
    Note: The contents of two files above are obviously linked, but are generated separately in SimLab/OptiStruct through two different post-processing actions. For more information on how to generate those files, please refer to the SimLab/OptiStruct user guide.
Once these files are available, and while pre-processing a Flux 2D project containing laminated magnetic non-conducting regions, the import may be executed as follows:
  • in the Physics menu, select Mechanical stress distributions;
  • then, choose command Import spatial distribution from SimLab/OptiStruct.
This action will open the Import spatial distribution from SimLab/OptiStruct dialog box. In its General tab:
  • provide the path to the Mesh file describing the support (.fem file), i.e., the first Simlab/OptiStruct file mentioned above.
  • provide the path to the Data file containing stress values on the support (.txt file), i.e., the second SimLab/OptiStruct file mentioned above.
  • provide a list of Regions with mechanical stress dependence, i.e., the Laminated magnetic non conducting regions with the Mechanical stress dependence option that will be influenced by the mechanical stress distribution imported as a spatial quantity.
  • provide a string representing the Name of the stress spatial quantity that will be generated through the import process.
Importing a stress distribution will also create entities that are only visible in the Data Import/Export context. More specifically, the import algorithm maps the mechanical stress values and the mesh support from the input files to the finite element mesh of the Flux 2D project and to the selected regions using a spatial quantity. Consequently, a Data support and a Data collection are created during the process.
Note: The mesh used in the structural mechanics simulation and stored in the .fem file doesn't need to be equal or similar to the mesh generated by Flux 2D in the project. However, it is recommended to use an identical base geometry in the structural mechanics simulation, to ensure that the mapping operations performed during the import will not yield unexpected results.
Thus, it is also possible to configure the following non-mandatory parameters in the Advanced tab:
  • the Data support name generated during the import;
  • the Name of the imported data collection generated during the import;
  • the Coordinate system used in Flux 2D that corresponds to the coordinate system implicit in the input files.
Finally, click the OK button to complete the mapping and the import. Flux 2D will then:
  • create a spatial quantity containing the mechanical stress distribution and
  • set active the Mechanical stress dependence option of the regions provided in the list. Their Constraint type parameter will also be set to Defined by a spatial variable card, and the generated spatial quantity will be used to describe their Equivalent uniaxial stress (MPa) .