Friction forces

For the tangential degress of freedomm there are three different force- and torque laws to be implemented.

(i) sliding friction
(ii) rolling resistance
(iii) torsion resistance
This split into four forces and torques (including the normal force) is an attempt to make the three force laws objective

Tangential forces.

To integrate the tangential contribution into the contact interaction, the developer needs to combine species.

The available models to compute the tangential interaction are:

• Sliding interaction
• Rolling and Torsion interactions
• non-Linear Tangential Contact Forces (Mindlin)

Reference:
S. Luding, Cohesive, frictional powders: Contact models for tension"