Defining a Drucker-Prager model

From the menu bar in the Edit Material dialog box, select MechanicalPlasticityDrucker Prager.
(For information on displaying the Edit Material dialog box, see Creating or editing a material.)
Click the arrow to the right of the Shear criterion field, and specify which yield criterion you want to define. See the following sections for more information:
- Linear Drucker-Prager Model
- Hyperbolic and General Exponent Models
If you are performing an Abaqus/Standard analysis, enter a value for the Flow potential eccentricity, $ϵ$ .
The eccentricity is a small positive number that defines the rate at which the hyperbolic flow potential approaches its asymptote. The default is $ϵ = 0.1$ for the exponent model, and if $ψ = β$ , it is set to $ϵ = ({d^{'} |}_{0} - {p_{t} |}_{0} \tan β) / ({\bar{σ} |}_{0} \tan β)$ for the hyperbolic model to ensure associated flow. See Extended Drucker-Prager Models, for more information.
If you selected Exponent Form from the list of Shear criterion options, you can toggle on Use Suboption Triaxial Test Data to request that Abaqus compute the material constants from triaxial test data at different levels of confining pressure. See General Exponent Model, for more information.
Toggle on Use temperature-dependent data to define data that depend on temperature.
A column labeled Temp appears in the Data table.
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.
In the Data table, enter the data relevant to your Shear criterion choice (not all of the following will apply):

Angle of Friction

If you selected Linear from the list of Shear criterion options, enter the material angle of friction, $β$ , in the p–t plane.

If you selected Hyperbolic from the list of Shear criterion options, enter the material angle of friction, $β$ , at high confining pressure in the p–q plane.

Enter the value in degrees.

Flow Stress Ratio

The ratio of the flow stress in triaxial tension to the flow stress in triaxial compression, K. $0.778 \leq K \leq 1.0$ . If you leave this field blank or enter a value of 0.0 is entered, Abaqus uses a default of 1.0. If you plan to define creep behavior, set K to 1.0.

Dilation Angle

If you selected Linear from the list of Shear criterion options, enter the dilation angle, $ψ$ , in the p–t plane.

If you selected Hyperbolic or Exponent Form from the list of Shear criterion options, enter the dilation angle, $ψ$ , at high confining pressure in the p–q plane.

Enter the value in degrees.

Init Tension

Initial hydrostatic tension strength, ${p_{t} |}_{0}$ . (Units of FL⁻².)

a

Material constant a.

b

Exponent b. To ensure a convex yield surface, $b \geq 1$ .

You may 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.
Select Drucker Prager Hardening from the Suboptions menu to specify hardening data for the Drucker-Prager model. See Defining Drucker-Prager hardening” for details.
If desired, select Drucker Prager Creep from the Suboptions menu to specify creep data for the Drucker-Prager model. This option is valid only if you have selected Linear from the list of Shear criterion options and are performing an Abaqus/Standard analysis. See Defining Drucker-Prager creep” for details.
If you toggled on Use Suboption Triaxial Test Data in Step 4, select Triaxial Test Data from the Suboptions menu to enter the triaxial test data. See Specifying triaxial test data for a Drucker-Prager material model” for details.
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).