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Re: Granular ratchetting explained
allow me a question about the way we compute the shear part. Following
the Cundall's model, no problem of ratcheting would arise since he
defines the branch vectors as radius*normal.
I recently checked PFC manual, and it defines shear with OC vector,
resulting in ratcheting. Maybe you'll find radius*normal in other
Cundall's papers, not sure, but at least PFC3D gives ratcheting.
Now in Yade if we avoid granular ratcheting we follow exactly the same
way. So, apart from ratcheting, why should the current length of the
interaction be preferred? Why this was introduced in the code?
I think it is often introduced by DEM programmers because it is somehow
intuitive, once you admit that particles can overlap each other, with a
"contact point" somewhere in the overlap. Current length is also used in
torque definition, whatever the definition of shear displacement.
Personally, I try to never use the words "overlap" or "penetration", and
refer to relative displacement of centers instead. The "overlap" concept
is not needed to derive the equations and it misleads people (another
example is the computation of void ratio : people sometimes tend to
remove the "overlapping" volume, which not suitable in most cases IMHO).
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