Damage evolution

When you create a damage initiation criterion in the Edit Material dialog box, select SuboptionsDamage Evolution to specify the associated damage evolution parameters.

(For information on entering damage initiation criteria, see Defining damage.)

Select the Type of damage evolution:

Displacement

Displacement damage evolution defines damage as a function of the total (for elastic materials in cohesive elements) or the plastic (for bulk elastic-plastic materials) displacement after damage initiation. This type corresponds to the Displacement at Failure field in the Data table.

Energy

Energy damage evolution defines damage in terms of the energy required for failure (fracture energy) after the initiation of damage. This type corresponds to the Fracture Energy field in the Data table.

Select the Softening method:

Linear

Linear softening specifies a linear softening stress-strain response for linear elastic materials or a linear evolution of the damage variable with deformation for elastic-plastic materials. Linear softening is the default method.

Exponential

Exponential softening specifies an exponential softening stress-strain response for linear elastic materials or an exponential evolution of the damage variable with deformation for elastic-plastic materials.

Tabular

Tabular softening specifies the evolution of the damage variable with deformation in tabular form and is available only when you select Displacement for the type. The Displacement at Failure field in the Data table is replaced by a Damage Variable field and a Displacement field, and you can add additional rows to define the displacements.

Select the Mixed mode behavior (for materials associated with cohesive elements only):

Mode-Independent

Mode-independent is the default selection.

Tabular

Tabular mixed mode behavior specifies the fracture energy or displacement (total or plastic) directly as a function of the shear-normal mode mix for cohesive elements. This method must be used when you select the Displacement type with cohesive elements.

Power Law

Power law mixed mode behavior specifies the fracture energy as a function of the mode mix by means of a power law mixed mode fracture criterion; it is available only when you select the Energy type with cohesive elements. The Fracture Energy field in the Data table is replaced by fracture energy in the normal mode and first direction and second direction shear mode components.

BK

The BK mixed mode behavior specifies the fracture energy as a function of the mode mix by means of the Benzeggagh-Kenane mixed mode fracture criterion. The Data table entries are the same as those for the Power Law.

Select the Degradation to determine how Abaqus combines damage evolution when multiple forms are active:

Maximum

The maximum degradation form indicates that the current damage evolution mechanism will interact with other damage evolution mechanisms in a maximum sense to determine the total damage from multiple mechanisms. Maximum is the default selection.

Multiplicative

The multiplicative degradation form indicates that the current damage evolution mechanism will interact in a multiplicative manner with other damage evolution mechanisms defined using this form to determine the total damage from multiple mechanisms. Other damage evolution mechanisms defined using the maximum degradation will interact with the combination of those using the multiplicative form.

Select the Mode Mix Ratio to use in conjunction with the Mixed mode behavior definition (for cohesive elements):

Energy

The energy mixed mode ratio defines the mode mix in terms of a ratio of fracture energy in the different modes. This definition is the default, and it must be used when you select Power Law or BK for the Mixed mode behavior.

Traction

The traction mixed mode ratio defines the mode mix in terms of a ratio of traction components.

When you select Power Law or BK for the Mixed mode behavior for cohesive elements, toggle on Power and enter the exponent in the power law or the Benzeggagh-Kenane criterion that defines the variation of fracture energy with mode mix for cohesive elements.

For the Hashin damage evolution model, the Data table contains the following fields:

• Fiber Tensile Fracture Energy

• Fiber Compressive Fracture Energy

• Matrix Tensile Fracture Energy

• Matrix Compressive Fracture Energy

For more information, see Damage evolution and element removal for fiber-reinforced composites.

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

A column labeled Temp appears in the Data table.

To define damage evolution 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.

Enter damage evolution parameters in the Data table.

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.

Click OK to save the damage evolution data and return to the material editor.