Contact Models in Altair MotionView

VKR

Hello,

Does anyone know what kind of theory is behind Impact and Poisson models for contacts in Altair MotionView? I would like to do some theoretical predictions before setting up the contacts.

Vishvam

Hello @VKR

Impact Model (Penalty-Based Contact) :

This model is based on Hertzian contact theory, where the contact force is defined using a combination of stiffness and damping.

Poisson Model (Restitution-Based Contact):

This model is based on coefficient of restitution (e), which determines the energy lost during a collision.
You can go through the following Motionsolve documentation for more details regarding each models:

Best Practices for Running 3D Contact Models in MotionSolve

Hope this helps!

Vishvam

Hello @VKR

Impact Model (Penalty-Based Contact) :

This model is based on Hertzian contact theory, where the contact force is defined using a combination of stiffness and damping.

Poisson Model (Restitution-Based Contact):

This model is based on coefficient of restitution (e), which determines the energy lost during a collision.
You can go through the following Motionsolve documentation for more details regarding each models:

Best Practices for Running 3D Contact Models in MotionSolve

Hope this helps!

VKR

Hello @Vishvam,

thank you very much for your reply. This is very helpful!

Do you perhaps have any recommendations for simulating aluminum-aluminum impact of flat surfaces?

Thank you very much :)

GTT Adam

Hi @VKR,

In general, the IMPACT method is used to capture most contact interactions. It is simple to understand and can easily have the stiffness increased if there is too much penetration. If contact is not the focus of the study, but is simply featured in the model, this is normally as intricate as you need to get with the contact definition.

However, if there are specific materials that are being used for contact and experimental data available, then the POISSON method could be explored for a more representative contact. The coefficient of restitution can often be found in literature and the stiffness can be tuned to match experimental data or observable trends.

Regardless of the method your choose, please follow the great link that @Vishvam posted for best practices. There are several tips about how to initially set values, adjust them, and when to activate advanced features.

Hope this helps!

Adam Reid

Orestis_YB

Hello @VKR,

@GTT Adam and @Vishvam already covered your question so I will just attach some more documentation that you might find useful while setting up contacts.

In Force: Contact you can find detailed documentation on how contact models work. More specifically in comment 5 you can find some recommendations for coefficient of restitution based on the materials in contact. In comment 6, it's explained how to maybe use the hertzian contact of two spheres to calculate the contact stiffness as a starting point. At the end of comment 6 thought it is highlighted that

"This should be considered a starting point for the penalty or stiffness value. You may need to tune this parameter, as high values of stiffness can degrade the performance of the solver. However, you may find that you are able to allow a smaller penalty, and thus more penetration, and still capture the overall system behavior."

I am attaching also this gearbox example model as a reference where contact stiffness was calculated by using the hertzian model of two cylinders in contact.

Hope this helps!

Best regards,
Orestes