Cohesion properties and the CCP formulation
Declan Mulroy
I've been re-reading several of the white papers on how Chrono calculates the contact forces, specifically with the CCP formulation. The cohesion properties inserted and used for the NSC formulation, how are those inserted into the CCP formulation? Are they added in via the friction cone? The other question is the rolling and sliding friction properties, how are those incorporated into the CCP formulation?
I've searched other papers posted and in one of them it stated the cohesion properties are inserted via the friction cone, but I just want to make sure. However, those articles as far as I could tell did not describe how the other friction properties are formally incorporated.
Additionally, I was trying to find where in the source code this occurs. Which function(s) in the repository is this located?
Finally, with regards to solving the contact forces. The CCP formulation is only calculated once not twice correct? The reason I ask is I have seen other formulations that use an LCP approach, that solve the impulse forces by using two LCP problems.
Thank you in advance,
Radu Serban
Declan,
Cohesion is indeed incorporated through a shift of the friction cone.
This is all done when projecting onto the friction cone (see ChConstraintTwoTuplesContactN::Project). This unilateral constraint is set up and used from ChContactNSC.h. Note that this is the implementation in the Chrono core module; a similar thing is done with a different implementation for Chrono::Multicore.
There’s one CCP solve per step.
--Radu
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Declan Mulroy
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