Contact formulation on collision

Mariah A.P.

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Apr 10, 2026, 4:17:51 AMApr 10

to ProjectChrono

Hi,

During a collision detection between two bodies, I wanted to know if it is possible to set on Chrono one of them as a rigid body, non deformable (NSC), and the other one as a deformable body, to focus on stress/strain behavior (SMC).

Thank you!

Dan Negrut

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Apr 10, 2026, 9:56:00 AMApr 10

to Mariah A.P., ProjectChrono

First, a clarification about what NSC and SMC control in Chrono.

NSC and SMC are contact methods, not rigid/deformable designations. They are set at the system level:

ChSystemNSC — complementarity-based, non-smooth contact (impulse/constraint)
ChSystemSMC — penalty-based, smooth contact (Hertzian springs, etc.)

Chrono does not mix NSC and SMC within one contact event. So the short answer to your question as literally posed is “no”.

However, what you likely actually want is achievable. If your goal is a rigid body colliding with a deformable body to study stress/strain, the right approach in Chrono is:

Use ChSystemSMC
Add your rigid body as a standard ChBody with a collision shape
Add your deformable body, e.g., a mesh of ChElementHexaANCF or ChElementShellANCF elements
Chrono supports contact between rigid bodies and FEA meshes. This gives you the behavior that perhaps you're after: one body behaves as a rigid collider, the other deforms and you can extract stress/strain from the FEA elements.

I hope this is helpful.

Dan

---------------------------------------------

Bernard A. and Frances M. Weideman Professor

NVIDIA CUDA Fellow

Department of Mechanical Engineering

Department of Computer Science

University of Wisconsin - Madison

4150ME, 1513 University Avenue

Madison, WI 53706-1572

608 772 0914

http://sbel.wisc.edu/

http://projectchrono.org/

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M. Pereira

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Apr 13, 2026, 5:40:17 AMApr 13

to ProjectChrono

Thank you for the clear explanation, I'll definetely try doing that!

You mentioned that the contact methods aren’t strictly “rigid” or “deformable,” but in practice, the Non-Smooth Contact (NSC) system treat all collisions as if the bodies were rigid, doesn't it?
I’m trying to model a gear system where a flexible (non-rigid) component pushes another gear forward. That gear is initially held in place, so tension builds up until it suddenly moves one tooth forward, like a snapping motion.
I’m concerned that NSC might not be the right approach for this kind of behavior, even though I’m simplifying things by applying a linear increasing torque to represent the flexible part.

I don't know if I could clearly explain the situation

M.

Dan Negrut

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Apr 13, 2026, 9:37:47 AMApr 13

to M. Pereira, ProjectChrono

You say “a flexible (non-rigid) component pushes another gear forward”.

Is there a need for the gear to be flexible?

If the gear deformations are small and your interest is in overall motion of a mechanism, I would simply work with rigid bodies and use a nice mesh for collision detection. NSC is a good place to start.

If this is for a watch design, then there is work that has been done in Chrono in this direction. You might want to reach out to Professor Alessandro Tasora, in Italy, he worked on this problem before.

Dan

---------------------------------------------

Bernard A. and Frances M. Weideman Professor

NVIDIA CUDA Fellow

Department of Mechanical Engineering

Department of Computer Science

University of Wisconsin - Madison

4150ME, 1513 University Avenue

Madison, WI 53706-1572

608 772 0914

http://sbel.wisc.edu/

http://projectchrono.org/