Enforcing Stability Settings During the Calibration

You can enforce material stability constraints during the calibration.

The stability settings described in this section enforce the stability of the material model during calibration. To define stability display ranges after a calibration, see Plotting Material Stability Data.

Note:

The option to enforce stability during calibration is only available in the analytical execution mode, see About Material Models and Execution Modes

See Also
About Material Stability
  1. From the Calibration Tools section of the action bar, click Calibration Options .
    The Calibration Options dialog box appears.
  2. From the commands section at the top of the Calibration Options dialog box, click Optimization Controls
    The Optimization Controls dialog box appears.
  3. From the Material Stability Settings expander, select Include stability computation in calibration.
  4. Specify the Stability penalty stiffness.

    Setting a proper penalty stiffness might require some numerical experimentation. In general, a higher penalty stiffness will do a better job enforcing the stability constraint; however, it might cause convergence difficulties. As a general rule start with a small penalty stiffness and slowly increase its value until you attain a calibration that satisfies both your accuracy and stability requirements.

  5. Specify the Stability mode:
    OptionDescription
    All deformation modes Checks stability at each point for every set of test data that is active during calibration. In addition, the app also creates internal deformation histories for all supported deformation modes using strain ranges and strain increments you specify in the Strain ranges expander.
    Test data only The app checks stability at each point for every set of test data that is active during calibration and does not refer to the optimization controls.

    For example, if you perform a calibration using a single set of uniaxial tension test data and with the Test data only option specified, the app only enforces the stability constraints for the uniaxial tension deformation mode at the test data points. If you perform the same calibration with the All deformation modes option specified, the app attempts to enforce the stability constraints for all deformation modes over the strain ranges you specified.

  6. Optional: If All deformation modes is selected, you can expand the Strain ranges options to directly modify the ranges and intervals over which stability checks are enforced. Three sets of ranges and intervals are included, and they correspond to stability checks for deformation modes as follows.

    Stability Plot Option Deformation Modes
    Nominal strain Adjusts range and intervals for stability plots of uniaxial, biaxial, and planar strain data.
    Volume ratio Adjusts range and intervals for stability plots of volumetric data.
    Shear strain Adjusts range and intervals for stability plots of shear strain data.