"LIGGGHTS WWW Site"_liws - "LAMMPS WWW Site"_lws - "LIGGGHTS Documentation"_ld - "LIGGGHTS Commands"_lc :c

:link(liws,http://www.cfdem.com)
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

:line

gran cohesion sjkr :h3

[Syntax:]

cohesion sjkr :pre

[LIGGGHTS vs. LAMMPS Info:]

This part of "pair gran"_pair_gran.html and 
"fix wall/gran"_fix_wall_gran.html
is not availabe in LAMMPS.

[Description:]

This model can be used as part of "pair gran"_pair_gran.html and 
"fix wall/gran"_fix_wall_gran.html

The simplified JKR - Johnson-Kendall-Roberts (SJKR) model adds an additional normal force
contribution. If two particle are in contact, it adds an additional normal force tending 
to maintain the contact, which writes 

F = k A, 

where A is the particle contact area and k is the cohesion energy density in J/m3. 
For {sjkr}, the sphere-sphere contact area is calculated as (http://mathworld.wolfram.com/Sphere-SphereIntersection.html)

A = Pi/4 * ((dist-Ri-Rj)*(dist+Ri-Rj)*(dist-Ri+Rj)*(dist+Ri+Rj) )/(dist*dist)

where dist is the distance between the particle centers.

If you are using the SJKR model, you must also define the cohesion energy density:

fix id all property/global cohesionEnergyDensity peratomtypepair n_atomtypes value_11 value_12 .. value_21 value_22 .. .
    (value_ij=value for the cohesion energy density (in Energy/Length3 units) between atom type i and j; n_atomtypes is the number of atom types you want to use in your simulation) :pre

IMPORTANT NOTE: You have to use atom styles beginning from 1, e.g. 1,2,3,...

[Restrictions:]

The cohesion model has been derived for the Hertzian Style, it may note be 
appropriate for the Hookean styles.
