virial stress calculation

Submitted by prasantud on Fri, 11/18/2011 - 12:19

Hi everybody,
Is there a easy way to dump the six components of virial stress.
As far as i know, following commands to be used for determining contact forces are not working properly.
1. pair/gran/local
node/601
2. stress/atom
node/361
regards,
Samantaray

Forums:

raguelmoon's picture

raguelmoon | Fri, 11/18/2011 - 14:26

Hi,
If you want to dump 6 stresses per layer then use these commands:
......
compute stresses all stress/atom
........
fix stressByLayer all ave/spatial 100 10 1000 z lower 0.02 c_stresses[1] c_stresses[2] c_stresses[3] c_stresses[4] c_stresses[5] c_stresses[6] file stress.profile
.....

where c_stresses[1] to c_stresses[6] are stresses along xx, yy, zz, xy, xz and yz.

Cheers,
Ram

Ram

prasantud | Fri, 11/18/2011 - 15:02

Hi Ram,
thanks for the reply, it works fine.
I have one more important question.
How to dump both tangential and normal contact forces.

I used following commands
compute forces all pair/gran/local pos id force
dump forcedump all local 10000 post7/dump.loss7f c_forces[1] c_forces[2] c_forces[3] c_forces[4] c_forces[5] c_forces[6] c_forces[7] c_forces[8] c_forces[9] c_forces[10] c_forces[11] c_forces[12]

The pair/gran/local command is not dumping normal forces and also dumping lot of zeros. node/601

Is there another way.
regards,
Samantaray

raguelmoon's picture

raguelmoon | Sat, 11/19/2011 - 08:23

Hi,
I checked it. May be there is problem with pair/grain/local. Let Christoph reply this question...
Best,
Ram

Ram

ckloss's picture

ckloss | Mon, 11/21/2011 - 12:57

Yes, there is a typo bug in compute pair/gran/local...Will be fixed by the end of the week in the next version!

Christoph

prasantud | Wed, 11/23/2011 - 07:16

Hi Chistoph,
Thanks for correcting the bug in pair/gain/local.
I request to add extra flag for the normal force between the contacts.
This is very important parameter. It will be difficult to redo all the procedures again
for this minor change.
Best wishes for LIGGGHTS.
Samantaray

ckloss's picture

ckloss | Thu, 11/24/2011 - 08:17

Hi Samantaray,

normal force can be extracted by post-processing the existing contact data because you know the contact normal, so that is what I would recommend. You can also change the implementation yourself.

Cheers, Christoph