LIGGGHTS® - User Forum

Hi all,

I want to delete all particles which have the stress larger than 10kPa, does anyone know which commands should I use?

Thanks very much.

Best,
Rachel

Dear all,

Good morning.

In my case, a mesh (plane, generated by gmesh) wall push the particle bed. However, I find the inconsistency of the total contact force on the wall by using two methods:

A) 1) fix wallleft all mesh/surface/stress; 2) variable fwlx equal f_wallleft[1]; 3) export it into the csv file
B) 1) compute cpw all wall/gran/local id pos force; 2) dump all components of cpw; 3) sum all forces in excel

The force by mesh/surface/stress is much different with the one by compute/wall/gran/local.

Dear colleagues,

I am facing a problems about deleting particles who have the interaction force with a stress wall (*.stl file) larger than 10kPa. My questions are:

1. How to monitor whether a particle have interaction with a stl wall and how to obtain the interaciton force or stress?

2. How to delete the particle when it has a particle/wall interaction stress larger than 10kPa?

Could anyone please give me any clues?

Best,
Zheng

Hi all,

I want to delete a certain fraction of particles in a region. I use the command "delete_atoms porosity" to realize this function.

From the documentation, I notice that 10% of particles inside a given region will be deleted if I use "delete_atoms porosity cube 0.1 123457". I am just not sure how to determine whether a particle belongs to the region? Based on the centre of the particle or based on othere criteria? Thanks.

Best,
Rachel

Hello,
I am running some tests using the python wrapper and would like to hide ALL
screen output from liggghts.

Is there any way to do this?

I am using the flags pre no and post no on my runs to hide some of the output
and echo none to hide line reads but I still have some output.
I also do not want to redirect the screen output to a file as the file would grow
rather large.

Thank you.

Hi,

To my understanding, Meff (effective mass) used in contact models can be calculated from "density" defined in

fix pts1 all particletemplate/sphere ...

but I have questions as follows:

1. I need to know how to define the mass for walls including mesh to be used in Meff.

2. please let me know If there is a way to directly define Meff used in hertz/stiffness or hooke/stiffness (I want to set it unity for simplicity).

Thank you

I am running simulations of a ring shear tester and I use the fix mesh/surface/stress/servo command.

I am not completely sure about the way to calculate the tangential shear stress from the values of forces and torques I obtain from LIGGGHTS. As result, I have a global vector with 9 components for access by various output commands. The first 3 components are equal to the total force on the mesh, the next 3 components store the total torque on the mesh.

Hello
while doing post processing, I wrote the commond : lpp dump*.chute
but it showed the following message
Command 'lpp' not found

Hey guys,

I use the fix bond/create/gran:
fix bondcr11 all bond/create/gran 10 1 1 0.5 1 100 prob 1 123457

The simulation works for a probability=1 but when I reduce the probability I get the segmentation fault.
*** Process received signal ***
Signal: Segmentation fault (11)
Signal code: Address not mapped (1)
Failing at address: 0xb8

I looked for this error but I don't know how to fix it. Does anybody have an idea?

Thanks for considering my request.

Hi all,

I am doing a triaxial test using LIGGGHTS. After I consolidated my sample in a cube to a constant confining pressure 50kPa, I want to set one boundary which can be penetrated by the small particles while keeping the big particles insides. During this process, the small particles will penetrate through the boundary suddenly and the cube sample will suddenly deform (the volumetric strain could be even 7%).