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[lammps-users] Force based friction test
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[lammps-users] Force based friction test

From: Raghu Ram <raghu.mmt@...24...>
Date: Mon, 20 Nov 2017 16:02:10 -0600

Dear LAMMPS users,

I am doing MD simulations for frictional studies (indentation and scratch tests) between aluminum surfaces. I have used fix indent (LAMMPS indenter) command and it worked good which is displacement controlled. I am  trying to simulate force based indenter to replicate the experimental setup. The indentation process looks fine and comparable to lammps indenter (displacement controlled repulsive indenter), but the scratch process is not working properly. 

I have used fix aveforce command and fix lineforce  command for indentation process and fix setforce (gives normal load) and fix move to scratch during scratch process. 

What I am seeing is the normal force on the indenter is not stable and it is dropping down to zero. I have also not observed any wear in the indenter (group of atoms). I am not sure what mistake I am doing?. Any suggestions will be appreciated. 

Here is the important portion of the code:


fix               4 top aveforce NULL v_force 0.0

fix               5 top lineforce 0.0 1.0 0.0

fix               6 top nve

I have used npt for substrate atoms


fix                4 top setforce NULL -0.08 NULL

fix                5 top move linear 0.05 0 0 units box

fix                6 top nve.

Thank you.



S. Raghuram Reddy
TUBAF, Freiberg, Germany.               
Cell : +49-17655446864