Cutting force-Reg

Hi everyone,

I am doing nanocutting simulation using NVE with the help of Tersoff potential. Everything seems to be fine except the cutting force which turns out to be fluctuating between negative and positive value even after 150000 time steps.

Below is the command I used for calculating cutting forces acting on tool
fix 4 fix setforce 0.0 0.0 0.0

velocity mobile create 300 58142275 temp new
velocity tool set -1 0 0 # sum yes units box

variable fx equal fcm(newtont,x)
variable fy equal fcm(newtont,y)
variable fz equal fcm(newtont,z)
thermo_style custom step temp pe press v_fx v_fy v_fz

where, Newtont is the region in tool.

Attatched is the input file and cutting forces obtained during simulation.
From research papers I came to know that it will stay on positive side after equibliration but it is not. Please help me to overcome this.

in.eg (3.45 KB)

force.jpg

Hi everyone,

I am doing nanocutting simulation using NVE with the help of Tersoff
potential. Everything seems to be fine except the cutting force which turns
out to be fluctuating between negative and positive value even after 150000
time steps.

Below is the command I used for calculating cutting forces acting on tool
fix 4 fix setforce 0.0 0.0 0.0
velocity mobile create 300 58142275 temp new
velocity tool set -1 0 0 # sum yes units box
variable fx equal fcm(newtont,x)
variable fy equal fcm(newtont,y)
variable fz equal fcm(newtont,z)
thermo_style custom step temp pe press v_fx v_fy v_fz

where, Newtont is the region in tool.

Attatched is the input file and cutting forces obtained during simulation.
From research papers I came to know that it will stay on positive side
after equibliration but it is not. Please help me to overcome this.

​have you visualized your simulation? it may not be doing exactly what you
are expecting it would do.

​axel.​

Yes sir, I have visualized my simulation. Its a nanocutting process in which a tool is used to cut the workpiece, it is doing fine but the forces alone are not stable

Yes sir, I have visualized my simulation. Its a nanocutting process in
which a tool is used to cut the workpiece, it is doing fine but the forces
alone are not stable

​well, then you should look again. from looking at your input, i *do* see
two obvious problems​.

1) due to using periodic boundaries in y, your tool not only interacts with
the top of your workpiece, but also with the bottom. there is no need to
use PBC in x either. i can clearly see atoms from the bottom being pulled
away.

2) your tool will stop moving as after it has hit the workpiece and
transferred its momentum, as there is nothing driving the continued
cutting. it looks like this is happening.

...and the use of temp/rescale doesn't make any sense to me either.

axel.