Defining constants for a user material

The following user subroutines allow you to create user-defined material models:

  • UMAT for mechanical material models in Abaqus/Standard.

  • VUMAT for mechanical material models in Abaqus/Explicit.

  • UMATHT for thermal material models in Abaqus/Explicit.

You can enter constants in the Edit Material dialog box for use in these subroutines. See the following sections for more information:

  1. From the menu bar in the Edit Material dialog box, select GeneralUser Material.

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

  2. If you are performing an Abaqus/Standard analysis, click the arrow to the right of the User material type field, and select the type of user material for which you are defining constants.

  3. If you are performing an Abaqus/Standard analysis, toggle on Use unsymmetric material stiffness matrix if the material stiffness matrix, ∂⁡Δ⁢σ/∂⁡Δ⁢ε, is not symmetric or, in the case of a thermal constitutive model, if ∂⁡f/∂⁡(∂⁡θ/∂⁡x) is not symmetric. This parameter causes Abaqus/Standard to use its unsymmetric equation solution procedures.

  4. If you are defining a mechanical or thermomechanical material, enter the Mechanical Constants in the Data table.

    For detailed information on how to enter data, see Entering tabular data.

  5. If you are defining a thermal or thermomechanical material, enter the Thermal Constants in the Data table.

    For detailed information on how to enter data, see Entering tabular data.

  6. Click OK 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).