LIGGGHTS® - User Forum

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

Hi evereyone,

I have a naive question. I try to generate a random cubical sphere packing by iterative growing from a cloud of spheres.
But I have two problems :

1) I don't know, How can I indicate the growing increment at each step for the spheres.
2) I don't know, if it is possible to put this increment equal to zero when the solid fraction or the compacity reaches a fixed value.

if you have few indications to give me, please don't hesitate.

Thanks

Regards
Jf

Christoph,

What do I do wrong using the "fix/rigid" in a LIGGGHTS simulation? I tried to produce the same input for LAMMPS and LIGGGHTS but I get an error with LIGGGHTS: (Line numbers are on) This input is for LAMMPS; for LIGGGHTS line 9 is commented out and line 10 and 15-19 are uncommented.

Thanks,
Christian

==========
1 # Simple rigid body system
2
3 atom_style granular
4 newton off
5 communicate single vel yes
6 units si
7 neighbor 0.002 bin
8

Hi Everyone

I am running a model of a drum with spheres in it. The drum is imported from an STL file. When I run this, I get the following warning repeatedly:

"WARNING: Dangerous build in triangle neighbor list."

Do I need to be concerned with this? Is there perhaps a problem with the STL file? I did notice that my spheres might be escaping the drum, but I need to double-check for a reason.

I could only find the following in the "fix_tri_neighlist.cpp" file:

//if a fix move/mesh/gran is registered, advise the user to increase skin safety (and eventually shorten time-step)