Add contact interaction

When a PneuNet is sufficiently inflated, the walls of adjacent chambers will come into contact with each other. However, Abaqus explicitly needs to be told to take this physical interaction into account; otherwise, the modeled result will have the walls simply passing through each other, as seen below:

Create interaction property

First, we create the type of interaction we want to model. In the model tree, double click on Interaction Properties and create a new property of the type "Contact."

Add Mechanical > Tangential Behavior from the dropdown menu, and make it frictionless.

Create interaction

Now we define where/how the above interaction type is going to apply. In the model tree, double-click on Interaction and create a new interaction of type "Self-contact (Standard)." Make sure that this interaction applies during the Pressure step, since that is when the walls begin to touch.

Now, we select the surfaces where the contact will occur. Select all the adjacent chamber walls in the actuator, by clicking on the relevant faces while holding down SHIFT on your keyboard. You will need to rotate your view at least once to select everything. Click the 'Done' button when finished.

One last "Edit Interaction" window will pop up. Use the default settings, seen below: