about gridconnection

Hello,

Can someone give me some advices?

yes, sure, ask the question better :-)
e.g. a MWE would be helpful.
Also please describe what the actual problem is. It seems that you do not want cracking of connections, but it is not clear at all and is too much guessing to spend time on actual answer..
What is normalCohesionguan and shearCohesionguan? (maybe the MWE would answer this)
What values have already you tried? What happens if you increase the cohesion 100 times? 1e6 times?...

cheers
Jan

Thanks for Jan.
What does MWE mean?
And my script includes two documents whcih all have many codes.
How can I pass it to you? Or type them here?
Thank you very much!

> What does MWE mean?

see [1]

Thanks for putting more details, but please try not to modify the original question. Instead, put the additional info as the next post and next time please spend a bit more time creating the question.

fixed in 'XYZxy' and value of gravity is nice, but instead please describe WHAT IS THE PROBLEM. From the question text, I don't know (I can just guess which I don't want).

Jan

[1] https://yade-dem.org/wiki/Howtoask

Thanks Jan very much.
MWE is this:

https://dropmefiles.com/jEj7z

there are two scripts. Name '1.py' is running first to obtain the particles in the pipe. After '1' completed, running '2.py' to set pipe and go on.
my problem is: when '2.py' is running in some time, some gridConnection between gridNode are cracking. I want the connection can not crack.
Thanks very much!

Thanks for clarification and for the scripts, it makes everything much easier.
I am not familiar with grid* stuff. It seems that the problematic connections use CohFrictMat and Law2_ScGeom6D_CohFrictPhys_CohesionMoment (which was not mentioned at all in the original question and is the most important information for the problem :-).
So the question could be simplified to "How to make CohFrictMat not to break". I am not familiar with it, so I cannot help you.. But now it should be easy for somebody famliar with CohFrictMat :-)
cheers
Jan

Thanks for Jan.
I read some information in
https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Law2_ScGeom6D_CohFrictPhys_CohesionMoment

It give the information:
===============================================================
If the maximum tensile or maximum shear force is reached and CohFrictPhys::fragile =True (default), the cohesive link is broken, and a_n, a_s are set back to zero. If a tensile force is present, the contact is lost, else the shear strength is F_s^{max}=F_n*tan(\phi). If CohFrictPhys::fragile =False, the behaviour is perfectly plastic, and the shear strength is kept constant.
=================================================================
Then I junmp to
https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.CohFrictPhys.fragile,

Then in script, I change:
---------------------------------
Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(setCohesionNow=True,setCohesionOnNewContacts=False)
--------------------------------
into
---------------------------------
Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(setCohesionNow=True,setCohesionOnNewContacts=False,fragile=False)
--------------------------------
When I run the script, the yade tells me : Ip2_CohFrictMat_CohFrictMat_CohFrictPhysfragile=False,setCohesionNow=True,setCohesionOnNewContacts=False)
AttributeError: No such attribute: fragile.

Would you give me advice how to set fragile=False?
Thanks a lot.

Hi xjin,

The script has errors, please check it first. Please try also putting everything into a single script.

Thanks,
Marcus

IPhys (CohFrictPhys which your doc link refers to) and Ip2 (Ip2_CohFrictMat_CohFrictMat_CohFrictPhys) are different things..
try to put fragile=False directly to the material definition[1]
Jan

[1] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.CohFrictMat.fragile

Thanks for Jan, I try it but failed.Maybe it is not suitable to use the gridconnection to simulate the soft continuous structure. I try another way to solve the simulation.
Thanks for Marcus, I can run my script in my ubuntu, and I pass the original scripts in the MWE.

> but failed

please always provide a relevant information.. did you get en error? what error? did it still crack?

Btw. how do you know the structure is cracking? Some numerical or just visual evidence? And what does "cracking" exactly mean? :-)

> Maybe it is not suitable to use the gridconnection to simulate the soft continuous structure

I don;t use it myself, but I had feeling they were created especially for this purpose :-)

cheers
Jan

>> Maybe it is not suitable to use the gridconnection to simulate the soft continuous structure

> I don;t use it myself, but I had feeling they were created especially for this purpose :-)

Correct. More exactly PFacets (built on the top of gridConnections) is a good fit for such thing.
Actually blocking all DOFs should solve all above problems if the pipe is a rigid thing...

@Xjin,
please read https://yade-dem.org/wiki/Howtoask carefully (both sections).

Bruno

Thanks for Jan and Bruno. Thanks for Marcus again.
Just now I try to putting everything into a single script as Marcus suggests, the simulation succeed.
Before, I creat particles by script '1.py' and O.save() the model. Then I run script '2.py' to creat gridconnection . In the top of scripy '2.py', I use O.load() to load the particles.When the gridconnection is created and the script '2.py' runs some time, some cohesive link is bresking (this is the 'crack' I refer before), though I set the fragile=false.
Now I creat the particles and gridconnection in one script and run it, the cohesive link will never break.
My YADE-version is 2018.02b.
I don't know the reason.May be the O.save() and O.laod() will load some parameters' missing?
The simulation succed, and I am so surprised and much appreciating for Jan, Bruno and Marcus so much！