How to calculate COF?

Hello everyone,

I have a question that I am sure it’s pretty easy but I have hard time get over it.

I am trying to model a friction model in order to calculate the coefficient of friction. I have a rigid body which moves on top of a plate. In order to calculate the COF I have to divide the horizontal force by normal force. I have the normal force applied to my rigid body and it’s known and fix. In order to calculate the horizontal force, I add the x component of the force on all atoms. However, the results doesnt make any sense.

Is there anyway that I can calculate the COF in LAMPPS itself?

Thank you in advance for your help.

you could define a variable to divide two sets of
forces, but that’s no different than what you are
doing. You need to make sure the forces you
are accumulating on the body or the plate make



Thanks for the response. If that calculation is correct, then I’m doing the following in order to save the forces:

compute 11 all property/atom fx fy fz

dump 10 lo-slab-layer custom 1000 run25/forceAllLowerLayer.* id type x y z fx fy fz

Is it anything else that I have to do?

Thank you in advance for your help.


The dump command by itself will write the forces
to a file. You’re not using compute 11.

You can use compute reduce to sum force components
if you wish (over atoms).