LIGGGHTS® - User Forum

Hi,

Hi all,

Just wondering if there is a way to directly specify values for normal and tangential elastic constants and viscous damping constants in an input script. If there is could someone direct me to the documentation where this is explained or an example script showing how someone has done this would be awesome.

Regards,

Alex.

Hi all,

I am a little confused about one issue: In liggghts, we can output the stress of the an atom using command "compute stress/atom". If we introduce the seepage force into the simulation using CFDEM engine, e.g. drag force, buoyant force. Does the calculated stress of atom include these seepage force, or it only includes the particle-particle and particle-wall interaction force?

Thank you very much.
Zheng

Hello all,

I would like to ask whether LIGGGHTS can be used for modelling continuous materials ? For example, modelling tensile test of aluminium specimen, then compare the stress-strain diagram with experimental data. Has anybody had experience with it ?

Thank you.
Vinh

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