About Material Models and Execution Modes

The three distinct computational modes available for computing a material's response curve are the analytical, numerical, and FE execution modes. Analytical execution mode is the fastest of the three, but it supports calibration for fewer material models and is subject to other limitations. Numerical execution mode is slower than the analytical execution mode but provides support for more material models. The FE mode is in general the slowest of the three options, however it offers the greatest range of application regarding model and material response complexity, and supports the same set of material options as the numerical execution mode. Only one execution mode can be active during a given a calibration job, but you can switch between the modes during a session. (see About Execution Modes and Simulation Models)

Switching between Execution Modes

If you are in the analytical execution mode and you switch to the numerical or FE execution modes, the app preserves your current material behaviors and material constants. However, if you are in the numerical or FE execution mode the app will not allow you to switch to the analytical execution mode unless the current set of material behaviors is also available in the analytical execution mode. For example, if you are in the numerical execution mode and you have a linear elastic material defined the app will not allow you to switch to the analytical execution mode since it does not support linear elastic materials. In order to switch to the analytical execution mode you need to change the material behavior to something supported by the analytical execution mode, such as hyperelastic.

Material Response Calculations in Analytical and Numerical Execution Modes

Both the analytical and numerical execution modes are driven by the test data you supply. They attempt to compute the material response, or primary stress response, for each value of primary strain included in the test data set.

For both the analytical and numerical execution modes you can choose the units that the app uses during the material response computations. Using proper units can improve the numerical robustness of the calculations. For example, if you would like to use mega-Pascals (MPa), you can set the length and mass units to millimeter and tonne respectively.

Material Response Calculations in FE Execution Mode

The FE simulation models are driven by the prescribed conditions you define in the models before they are imported into the app. They attempt to compute the material response at each time data point include in the imported test data set.

See About Material Calibration from Finite Element Simulation Models for a discussion on how units are handled for imported FE models.

Material Parameters Bounds

All material models have ranges of valid parameters for which the app can calculate a proper material response, though it is sometimes difficult to deduce what those ranges are. As part of defining the parameters for a material model, you can set bounds on the allowable values for the parameters that the app considers during a calibration. One advantage of setting bounds is the reduction of the size of the design space that the app explores, which can reduce the wall clock time for a calibration. Another advantage is that you can help ensure that only physically reasonable values of material parameters are used. If the app encounters a set of material parameters during a calibration that are not valid for the current material model, the app attempts to move the design search space away from these material parameters and continue with the calibration. If the app encounters a set of material parameters during a response plot calculation that are not valid for the current material model, it returns an error message and plots a zero response.

Import of Existing Material Models

You can import material parameters from existing material models into the Material Calibration app. The imported material models can either be 3DEXPERIENCE material objects or materials defined in anAbaqus input file snippet. Importing an existing material model can be helpful for calibrations where you expect some or all of the behaviors in the imported material to be good matches for the test data in the current calibration session.