Hey,
why does LIGGGHTS exactly have now the epsd3? In my oppinion if you want to use hertz contact law you have to use it, so that the coefficient of rolling stiffness is independent on normal stiffness, because normal stiffness changes all the time. A problem on EPSD3 is, if you define one rolling stiffness for all contacts you have the same rolling stiffness for two big particles as for a big and a very small particle. Is this still physically? Is it then still scale independent? Because it should be always scale independent.
Also I don't understand why now again for EPSD3 there is a damping value, which was missing in EPSD2?
So what is the idea of EPSD3?
kind regards,
joshua
aaigner | Fri, 10/30/2015 - 15:13
Who said that it is a kind of EPSD2?
Hi Joshua!
I can't find any reference to EPSD2? Is there somewhere a wrong link?
EPSD3 is the same as EPSD, but the (originally) hard coded prefactor for the calculation of the rolling stiffness from the paper of Ai et al. can be modified. Nothing more...
Concerning that particle size problem: Check the docu again. The rolling stiffness depends on the particle radius.
The damping coefficient comes from the original model EPSD. This one is a Elastic-Plastic Spring-Dashpot model. To be honest, EPSD2 has the wrong name. It should be more ES (it is not plastic and has no dashpot, it is just a non-linear spring for HERTZ)
Bests
Andreas
JoshuaP | Sun, 11/01/2015 - 17:49
ah ok its just the prefactor.
ah ok its just the prefactor. But EPSD2 has a maximum limiting torque and at that point the plastic part starts, or am I wrong? So its just the damping that is missing?
kind regards
Joshua