Specifying a crushable foam model

You can use the crushable foam model to model the enhanced ability of a foam material to deform in compression due to cell wall buckling processes. This model is based on the assumption that the resulting deformation is not recoverable instantaneously and can be idealized as plastic for short duration events. See Crushable Foam Plasticity Models, for more information.

  1. From the menu bar in the Edit Material dialog box, select Mechanical Plasticity Crushable Foam .

    (For information on displaying the Edit Material dialog box, see Creating or editing a material.)

  2. Click the arrow to the right of the Hardening field, and select a hardening model:

    • Select Volumetric to specify a model that assumes that the yield surface is controlled by the volumetric compacting plastic strain experienced by the material.

    • Select Isotropic to specify a model that uses a yield surface that is an ellipse centered at the origin in the p–q stress plane. The yield surface evolves in a self-similar manner, and the evolution is governed by the equivalent plastic strain.

  3. Toggle on Use temperature-dependent data to define data that depend on temperature.

    A column labeled Temp appears in the Data table.

  4. Click the arrows to the right of the Number of field variables field to increase or decrease the number of field variables on which the data depend.
  5. In the Data table, enter the data relevant to your Hardening choice from Step 2 (not all of the following will apply):

    Compression Yield Stress Ratio

    Yield stress ratio for compression loading, k = σ c 0 / p c 0 ; 0 < k < 3 . Enter the ratio of initial yield stress in uniaxial compression to initial yield stress in hydrostatic compression.

    Hydrostatic Yield Stress Ratio

    Yield stress ratio for hydrostatic loading, k t = p t / p c 0 ; k t ≥ 0 . Enter the ratio of yield stress in hydrostatic tension to initial yield stress in hydrostatic compression, provided as a positive value. The default value is 1.0.

    Plastic Poisson's Ratio

    Plastic Poisson's ratio, ν p ; - 1 < ν p ≤ 0.5 .

    Temp

    Temperature.

    Field n

    Predefined field variables.

    You might need to expand the dialog box to see all the columns in the Data table. For detailed information on how to enter data, see Entering tabular data.

  6. Select Foam Hardening from the Suboptions menu to define hardening data for the crushable foam model. See Defining crushable foam hardening” for details.
  7. If desired, select Rate Dependent from the Suboptions menu to specify strain-rate-dependent material behavior. See Defining rate dependence for a crushable foam plasticity model” for details.
  8. Click OK to create the material and to close the Edit Material dialog box. Alternatively, you can select another material behavior to define from the menus in the Edit Material dialog box (see Browsing and modifying material behaviors, for more information).