A model change interaction allows you to deactivate and reactivate elements to simulate removal of part of the model, either temporarily or for the remainder of the analysis. You can create a model change interaction in all Abaqus/Standard steps except for static, Riks steps and linear perturbation steps. For a detailed discussion, see “Element and contact pair removal and reactivation,” Section 11.2.1 of the Abaqus Analysis User's Guide.
To define a model change interaction:
From the main menu bar, select Interaction
Create.
Tip:
You can also create a model change interaction using the 
tool in the Interaction module toolbox.
In the Create Interaction dialog box that appears, do the following:
Name the interaction. For more information about naming objects, see “Using basic dialog box components,” Section 3.2.1.
Select the step in which the interaction will be created.
Select the Model change type of interaction.
Click Continue to close the Create Interaction dialog box.
The Edit Interaction dialog box appears.
Specify the model change definition.
Choose Region to define the region for the model change interaction for the current simulation.
Choose Restart to allow element or contact model changes in a subsequent restart analysis. Use this model change definition when there are no other model change interactions present. Do not use this definition if you deactivated contact pairs in the first analysis step, or if you created contact pairs after the first analysis step.
If you selected the Region model change definition, perform the following steps:
Select the region type and region.
Select Geometry to use model geometry for the model change region, click 
to select the region, and make your selection in the viewport.
Select Skins to use skins for the model change region, and click to select the region. From the prompt area, select (pick entire skin) or (pick partial skin), then make your selection in the viewport. If the selected part has multiple skins, Abaqus/CAE displays the ambiguous picking options in the prompt area while you make your selection.
Select Stringers to use stringers for the model change region, and click to select the region. From the prompt area, select (pick entire stringer) or (pick partial stringer), then make your selection in the viewport. If the selected part has multiple stringers, Abaqus/CAE displays the ambiguous picking options in the prompt area while you make your selection.
Select Elements to use elements for the model change region, and click to select the region. From the prompt area, select individually or by angle, then make your selection in the viewport. The mesh must be visible to select elements. For more information on this selection method, see “Using the angle and feature edge method to select multiple objects,” Section 6.2.3.
For all region types, you can use an existing set to define the region. On the right side of the prompt area, click Sets. Select a valid set from the Region Selection dialog box that appears, and click Continue.
The default selection method is based on the selection method you most recently employed. To revert to the old method, click Select in Viewport or Sets on the right side of the prompt area.
Select the activation state of the region elements.
Select Deactivated in this step to deactivate the selected region in the current step.
Select Reactivated in this step to activate the selected region in the current step. In subsequent steps you can select this option to reactivate the selected region if it was previously deactivated.
If you selected Reactivated in this step, you can toggle on Reactivate elements with strain (if applicable) to include strain for reactivated stress/displacement elements. Toggle this option off to reset the elements to the initial strain configuration.
Click OK to create the interaction and to close the editor.
Symbols that represent the model change interaction that you just created appear in the viewport. For more information, see “Understanding symbols that represent interactions, constraints, and connectors,” Section 15.10.
