LIGGGHTS® - User Forum

Hello Friends

I am doing a small exercise to match the axial direction stress (sigma_zz) using the following two commands
(1) ave/time
(2) stress/atom

In order to calculate the axial stress from ave/time, perhaps I need to divide the z-direction force with piston area.
And from stress/atom command, I guess, will get directly the axial stress (sigma_zz) by using the following snippet

I'm setup a simulation where I'm pouring particles into a geometry to form a stack of particles. The particles are the agglomerating together with a cohesion model and I notice that the computational resources is increasing with increased number of particles (as one would expect).

For many of these particles they will not move anymore since they are just agglomerated together and have many contacts so I would like to skip the calculation on these particles and just freeze them instead such that Liggghts does not calculate the contact forces and they will then just act as a wall.

Hi Experts,

I can´t solve the task to write the contact forces between particles in a defiend region. I tried it with:

region comp block -0.075 0.075 0.0 0.075 0.015 0.03 units box

group comp_group region comp

compute Force comp-group pair/gran/local id pos force

Hi, I have a question, I know that in LIGGGHTS WITH BONDS there are two forms of fracture, my doubt is that it means that value of " $c " y {" rb "}
variable rp equal 0.015625 #Radio de la particula
variable d equal 2*${rp} #Diametro de la particula
variable rb equal 0.8*${rp} **************************** What happens physically if I increase this value?
variable I equal 0.25*PI*${rb}*${rb}*${rb}*${rb}
variable A equal PI*${rb}*${rb}
variable kn equal 2*$Y/$d # comportamiento del grano 3.2e8 tesis 1e10

Hi everyone
I want to simulate a steel plate that measures the particles underneath by putting the force on it and measure the amount of stress and displacement of particles below it. What do you think is best for simulating this steel plate? Should I define a wall and rigid it?
thanks

Hello :
I have a problem, the write_restar and read_restar command worked correctly (to restart the simulation from file.restart), for simulations without bonds, but in my code that has bonds (bond style gran), it does not allow me to read the file with the "read_restart file.restart" command, sends me error: segment violation.
Can you help me solve this problem please?

it is necessary to eliminate the create_atoms, and lattice in this code?

thanks.
I attach my code

Hello,
As a part of my project i'm dealing with sand of less particle size. I got an error saying that volume expectancy too low and i tried to change units but I'm not succeeded. Here i attach my part of code.
Thank you.

### Initialization

# Preliminaries
units si
atom_style sphere
boundary f f f
newton off
communicate single vel yes

# Domain
region reg block -0.320 0.320 -1.960 1.460 -0.290 0.335 units box
create_box 3 reg

### Setup

Hello
I have done one liggghts simulation. Now I want to resume the same simulation not from starting but from where I left last time.
Can I do this in Liggghts.

hello LIGGGHTS Experts,

I have to compute stress and strain for particles.
I tried calculate stress by command:
fix stress all ave/euler nevery 1000 cell_size_relative 4.5 parallel no
and
collected the result by:
dump damp all custom 1000 post/dump*.liggghts id f_stress
but I recived following error:
ERROR: Dump custom fix does not compute per-atom info (../dump_custom.cpp:1383)

How to correctly dump this results?
Can I calculate the strain and stress for a particles in other way?

Best wishes,
Agnieszka

Hello,
I have problem when building liggghts. the makefile.user have been changed as mentioned in the installation document. I have not compilled VTK seperately. So i did the following changes in makefile.user:

USE_VTK = "ON"

VTK_INC_USR=-I/home/liggghts/vtk/include

VTK_LIB_USR=-L/home/liggghts/vtk/lib

So this should automatically download and install VTK. But i am getting the following error.