# On Setforce, Addforce and Aveforce

Hi,

Please, l have been simulating cutting phenomena using LAMMPS (- using a tool to cut a workpiece).

I obtained good ploughing/cutting phenomena when l use the setforce option of fix and setting a velocity for the tool to approach the workpiece, but l guess the cutting forces obtained are wrong. I used the following:

velocity tool set 1.0 0 0 sum yes units box

fix 6 tool setforce 0.0 0.0 0.0

Since l fixed the tool atoms to 0.0 (fx, fy, fz all set to zero), and l want to be able to evaluate the tool atoms forces l tried using :

fix 6 tool setforce NULL 0 NULL

to set fy to zero and obtain values for fx and fz (fy is to approx. zero in orthogonal cutting). This eventually didn’t work.

My use of addforce/aveforce didn’t help either.

Where could l be missing it out?

Thanks.

Jide

Hi,

Please, l have been simulating cutting phenomena using LAMMPS (- using a
tool to cut a workpiece).

I obtained good ploughing/cutting phenomena when l use the setforce option
of fix and setting a velocity for the tool to approach the workpiece, but l
guess the cutting forces obtained are wrong. I used the following:

velocity tool set 1.0 0 0 sum yes units box

fix 6 tool setforce 0.0 0.0 0.0

Since l fixed the tool atoms to 0.0 (fx, fy, fz all set to zero), and l want
to be able to evaluate the tool atoms forces l tried using :

fix 6 tool setforce NULL 0 NULL

to set fy to zero and obtain values for fx and fz (fy is to approx. zero in
orthogonal cutting). This eventually didn't work.

My use of addforce/aveforce didn't help either.

Where could l be missing it out?

the fix stores the total force on the atoms before they are overwritten.
you can access those as f_6[1], f_6[2], f_6[3] for example in thermo
output. for details see the lammps documentation about outputting
data from fixes.

cheers,
axel.