LIGGGHTS® - User Forum

hi all ! i am new comer in liggghts. i made a box and then divided it into two parts by importing an mesh wall(STl file).
I poured the particles on one side of the box. When i applied wiggle command the particles penetrate into the imported wall and cross it. i want the partcles should not cross the wall. there is my input file. If anybody help me i will be thankful.
sajjad

# Wall import from CAD

atom_style granular
boundary f f f
newton off
atom_modify sort 0 0

communicate single vel yes
units si

region reg block -0.01 0.51 -0.01 0.25 -0.01 1.31 units box

I use a geometry defined by an STL file and I move downwards another rectangular plane in order to wipe out some volume from atoms. In this empty volume I create some new atoms and I want to remove the former plane that separates the new atoms from the others.

When I unfix this rectanglular plane I receive a segmentaition fault (see below).

What I'm doing wrong? Is it possible to unfix wall/gran/hooke/history?
Or is there a better strategy to:
1.) pour a certain no. of particles in a STL defined geometry
2.) create an empty region keeping the no. of particles const.

Hi LIGGGHTS users,
I have one simulation box and it is divided by mesh wall into two boxes. One box is filled with two types of particles and when I wiggle it using wiggle command the particles cross the mesh wall and come into the other box.
Please anybody can troubleshoot the error? Thanks in advance.
Best,
Ram

Hi Christoph,
Could you please let me know, if LIGGGHTS can help me to run a triaxial compression test on a cylindrical shaped assembly of particles. Lateral wall under constant pressure, fixed bottom, and strain(velocity) controlled loading at the top. Any response from you will help. Thank you in advance.
Regards,
Carlos

Hi Everyone

The "dump custom" has the option for writing "fx fy fz". I assume these are the resultant total unbalanced force per sphere.

Is it possible to dump the contact forces (between spheres) and the contacts' positions?

Thank you

Alexander

Hi Christoph,

Concerning the stress computed with the command: mesh/gran/stressanalysis

In my simple compression test, I have these lines:

fix topwall all mesh/gran/stressanalysis topwall.stl 1 1. 0. 0. 0. 0. 0. 0. # Insert top wall
fix bottomwall all mesh/gran/stressanalysis bottomwall.stl 1 1. 0. 0. 0. 0. 0. 0. # Insert bottom wall

fix wall all wall/gran/hertz/history 1 0 mesh/gran 2 topwall bottomwall #Contact properties

fix F_movetop all move/mesh/gran linear 0. 0. -0.0001 units box topwall 1 #Wall motion

Hi everyone,

I try to make a simple compression test (see different attached files) from a cohesion sphere packing. Therefore, the top wall modeled by mesh is moved down.

But I have a strange simulation (you can run it from the attached file), there are not stresses computed (see ./post/Stress_file-*) on the top wall. Moreover the top wall only push some spheres.

I am a beginner, so it is possble that I done a mistake. if anyone can explain me it, I will be fine for me.

Thanks
Jf

Hi friends,
I found this error in new liggghts-1.1.2. The same file is working in old version without any error.

WARNING: STL face normals were not normalized, normalizing
Mesh calculations running. This may take a while...ERROR: STL import failed because triangles #0 (line 1) and #960 (line 6721) are duplicate
[ram@localhost rect]$

Please anybody there who can figure out the error...?!
Best,
Ram

I have downloaded the tar ball for version 1.1.1, I am struggling with the make fedora command in the /src directory

Operating system: Fedora 13 – 32 Bit

+ Install paraview by typing "sudo yum install paraview" in a console – only works if i run the command as root
+ Install Open MPI by typing "sudo yum install openmpi openmpi-devel" in a console – only works if i run the command as root

Updated the sudoers file to allow the my username...

I think paraview & Open MPI is installed correctly will it make a difference if i install as root?

Is it possible to use two different movements (e.g. wiggle and linear) on one mesh object?

I applied two different wiggle movements (0.0005 NULL 0.0003 and NULL 0.0007 NULL) with different periods on the object and is works. In addition I wanted to move the object linear while still "wiggling" but the wiggle stopped. Any suggestions?

Regards, Christian