How are nonlinear material files created?

Creating a nonlinear material file:

  • With a standard text editor create a file in the program directory where the other material files (*.mtl) are located. If you are dealing with a program that does not have a material folder already then it is a good idea to create one.
  • Create three columns of numbers using the following format:
    Point Number X coordinate Y coordinate
  • The first nonlinear material point has to be 1 0.0 0.0 unless the material is a permanent magnet. 10-15 points will create a good nonlinear curve. The end point for a 1st quadrant curve takes the slope from the last two points and continues the same slope after the last point.
  • If you are making a BH curve and are given the hysteresis loop, use an average of the two paths to define the curve (mean BH curve).
  • For permanent magnets, a second quadrant curve is defined and must start at y=0 and end at x=0. At least 3 points are recommended for a straight-line model.
  • Save the new material file with the extension *.mtl (no character limit). The material is now defined and ready to be loaded into your model.

Reading and Viewing the new nonlinear material file:

  • Before loading in your new material, make sure the units settings are the same as the ones that were used to create the material lists. For example if you used Gauss and Oersted to define the material, then make sure the units are set to Gauss and Oersted in the Utilities> Units Setup window. This information will not be passed in to the program from the file. Instead the program will assume it is reading in whatever units the settings are at.
  • To load in your new material open up the materials list and select a material that will not be used in your model. You will replace this material with your new one. Click on File>Load Nonlinear Curve and select your new material.
  • When you load in this new material the name will not change. You must do this and click on the Apply button.
  • Confirm the curve looks correct by opening up the materials list and clicking on the nonlinear curve editor as the points entered are defining a spline-fitted curve.
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