Maximum or quadratic nominal strain damage

The Maxe and Quade damage initiation criteria are used to predict damage initiation in cohesive elements where the cohesive layers are defined in terms of traction-separation. Both forms evaluate the strain ratios between a given strain value and the peak nominal strain value in each of three directions. εno, εso, and εto represent the peak values of the nominal strain when the deformation is either purely normal to the interface or purely in the first or the second shear direction, respectively. The Maxe criterion is based on the maximum value of the three ratios, whereas the Quade criterion is based on a quadratic combination of all three ratios.

Context:

For more information, see Defining the constitutive response of cohesive elements using a traction-separation description.

  1. From the menu bar in the Edit Material dialog box, select MechanicalDamage for Traction Separation LawsMaxe Damage or Quade Damage.

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

  2. If you are using the extended finite element method (XFEM) to model fracture, you can specify the crack propagation direction when the damage initiation criterion is satisfied. The crack can extend at a direction Normal to the local 1-direction (default) or Parallel to the local 1-direction.

  3. Enter the Tolerance. The value should be equal to the tolerance within which the damage initiation criterion must be satisfied.

  4. Select the arrow to the right of the Position field, and select the method for computing the stress/strain fields ahead of the crack tip to determine if the damage initiation criterion is satisfied and to determine the crack propagation direction (if needed):

    • Select Centroid to use the stress/strain at the element centroid.

    • Select Crack tip to use the stress/strain extrapolated to the crack tip.

    • Select Combined to use the stress/strain extrapolated to the crack tip to determine if the damage initiation criterion is satisfied and to use the stress/strain at the element centroid to determine the crack propagation direction (if needed).

  5. To define material damage data that depend on temperature, toggle on Use temperature-dependent data.

    A column labeled Temp appears in the Data table.

  6. To define behavior data that depend on field variables, click the arrows to the right of the Number of field variables field to increase or decrease the number of field variables.

    Field variable columns appear in the Data table.

  7. Enter damage parameters in the Data table:

    Nominal Strain Normal-only Mode

    Nominal strain at damage initiation in a normal-only mode.

    Nominal Strain Shear-only mode First Direction

    Nominal strain at damage initiation in a shear-only mode that involves separation only along the first shear direction.

    Nominal Strain Shear-only mode Second Direction

    Nominal strain at damage initiation in a shear-only mode that involves separation only along the second shear direction.

    Temp

    Temperature, θ.

    Field n

    Predefined field variables.

    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.

  8. Select SuboptionsDamage Evolution to define the material degradation that takes place once damage begins.

    For more information, see Damage evolution.”

  9. Select SuboptionsDamage Stabilization Cohesive to enter viscous coefficients and improve the model convergence.

    For more information, see Damage stabilization.”

  10. Click OK to exit the material editor.