LIGGGHTS® - User Forum

LIGGGHTS® related topics can be discussed here: discussion about models, installation, feature requests and general discussion

Simultion prematurely ending

Submitted by Mishal on Tue, 03/08/2022 - 20:26

Hi Guys

Please refer to the attached input script.
The first 63 lines define the attributes of the simulation thereafter the rest of the input file just consists of moving the mesh based on results I attained from my Matlab simulations. The simulation runs for only about 0.589 seconds, however the full simulation should be 30 seconds.

If I remove all the movement of the mesh the simulation time runs without giving any issues.
The below is the last part of the terminal output.

rotate/variable does not exist

Submitted by Mishal on Mon, 02/28/2022 - 18:49

Hi Guys

I am trying to use the rotate/variable command as per the below implementation.

fix move2 all move/mesh mesh cad rotate/variable origin 0. 0. 0. axis 1. 0. 0. omega 1

I get the following error when trying to execute my code.

ERROR: Variable name 1 for fix move/mesh rotate/variable does not exist (../mesh_mover_rotation.cpp:174)
(../mesh_mover_rotation.cpp:174)

Can someone please assist with the issue at hand?

Edinburgh contact stiffnesses

Submitted by kees_bulk on Fri, 02/25/2022 - 13:33

Hi,

I am working with the EEPA/Edinburgh contact model and due to the lack of doc something is unclear to me.

There are two input stiffnesses called CoeffAdhesionStiffness and UnloadingStiffness. I was unable to exactly determine what the value of the CoeffAdhesionStiffness (kn2kc) should be as it is not used the same way in the original work by Morrissey. In the code it is used to multiply with the loading stiffness to get the adhesion stiffness:

k_adh = kn2kc[itype][jtype] * kn

Multiple fix move/mesh commands

Submitted by Mishal on Thu, 02/24/2022 - 12:22

Hi Guys

This is just my baby steps for a more complex model which I would like to simulate.

I am trying to move a mesh translationally and rotationally at the same time.
Currently I am using the chute_wear model to achieve this.

The code that I am using is shown below, only the rotational movement is being produced.
How can I achieve the motion?

fix move all move/mesh mesh cad wiggle amplitude -0.01 0. 0. period 0.02
fix move all move/mesh mesh cad rotate origin 0. 0. 0. axis 0. 0. 0.1 period 0.05

Bad mesh, Can't continue

Submitted by Asset Aliyev on Wed, 02/23/2022 - 19:33

Hello everyone!
I have a problem with compiling a script in LIGGGHTS due to problems with STL file. I have tried many CADs, such as SolidWorks, Blender, Salome, but all the constructions can't be compiled with an error "Bad mesh, Can't continue".
It works well in Aspherix by using element_exclusion_list command due to excluding one triangle. However, in LIGGGHTS I can't fix this problem.

fix move/mesh command, for varying motion

Submitted by Mishal on Wed, 02/16/2022 - 19:13

Hi Guys

I am new to LIGGGHTS. I have ran through some of the examples.

I would like to know if the "fix move/mesh command" can be used to move mesh at a specific acceleration. The movement and acceleration will vary according to time and the data is kept on an excel spreadsheet.

Kind regards
Mishal Mohanlal

Non uniform grouping

Submitted by SHUBHAM AGARWAL on Tue, 02/08/2022 - 00:48

Hello
I am using LIGGGHTS-flexible fibres.
I my simulations I need to group certain atoms based on a spatially non uniform function. Since difficult to implement in LIGGGHTS directly, I plan to extract the atom IDs using a Python/Matlab script, then define grouping of those specific atoms. I have following two questions in this regard:
1) Is it possible to use group command such that I can group specific atoms read from a text file ?
2) What is the template to store atom IDs in such a text file ?

Any suggestions will be highly appreciated

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