Yade

Help for porosity, apply pressure, erase, get stress

Asked by liucheng83

Hi,
I 'm writing a code to create packing, I have some confuse, long for somebody can help to solve.
1, case one:a deep cavation of drill, how can I model the soil layer with the desired stress and porosity? whether I must use the real radius of clay ,such as 0.075mm or littler, and if I didnot use the real radius, how to give the E,v ,c, fri,density and so on?
2, what is the best way to get stress or prosity in some local volume, does predicates can do it? And how to do, is there an example?
3, when I use Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(setCohesionNow=True,setCohesionOnNewContacts=1), I have a question, whether I can use the 'setCohesionNow=false,setCohesionOnNewContacts=1' when packing with gravity and apply pressure on top of soil layer, and changes it to
 'setCohesionNow=true,setCohesionOnNewContacts=0' later, is it possible to do that?
4, how to apply constant pressure on top of soil layer, and then delete some particle in a cylinder volume like drilling, can somebody give me some example, I cannot get through the documentation, whether ForceEngine() or erase() can do that, thank you!

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Anton Gladky
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Bruno Chareyre (bruno-chareyre) said : 		#1

Dear LiuCheng,
The scope of your questions is so large that you may discourage people from trying to answer (I'm not trying to discourage anybody).

For 3), yes you can change the cohesion flags after some iterations.

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liucheng83 (lcheng83) said : 		#2

Dear bruno,
Thank you for your remind.
I guess somebody can give me some hint for one of my question, not all.

For 3), yes you can change the cohesion flags after some iterations.
Do you mean using "lable" ?

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Anton Gladky (gladky-anton) said : 		#3

> For 3), yes you can change the cohesion flags after some iterations.
> Do you mean using "lable" ?

You can, but it will take an effect only on newly created contacts,
not existing.
Please, see an answer 197661 [1]. It is something similiar.

[1] https://answers.launchpad.net/yade/+question/197661

Anton

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Bruno Chareyre (bruno-chareyre) said : 		#4

I beg to disagree Anton. ;)
Here the flags are functor flags, not material parameters.
If "setCohesionOnNewContacts", cohesion is assigned when new contacts appear (as the name suggests)
If "setCohesionNow", however, shear strentgh is assigned to all contacts, not only new ones.

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Jérôme Duriez (jduriez) said : 		#5

About your question 1), Liucheng83

- Generally, the real "radii" of the simulated geomaterials are not used in DEM simulations, because it would lead to a number of particles that computer can not deal with (too slowly in fact). So you will probably have to increase this "radius"

- for the mechanical properties, give a serious look at the kind of warning here https://www.yade-dem.org/doc/yade.wrapper.html#yade.wrapper.ElastMat. The link between the mechanical properties of YADE simulations, and mechanical properties that you know from continuum mechanics, can be no direct at all. You should find some information in previous answers (even if I could not find quickly a link)

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liucheng83 (lcheng83) said : 		#6

Thank you all,
About your question 1),
        -Hi, jduriez. Did you mean I have to use the E ,v, c,fri, with a coefficent multiplying it?
       and If I takes Capillary Fore into account, the formula has to be changed? I'm confused about it.

About your question 3),
        -Hi,Anton. what do you think of the information from bruno-chareyre
        I beg to disagree Anton. ;)
        Here the flags are functor flags, not material parameters.
         If "setCohesionOnNewContacts", cohesion is assigned when new contacts appear (as the name suggests)
        If "setCohesionNow", however, shear strentgh is assigned to all contacts, not only new ones.

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Best Anton Gladky (gladky-anton) said : 		#7

2012/5/25 liucheng83 <email address hidden>:
> Question #198294 on Yade changed:
>
> About your question 3),
>        -Hi,Anton. what do you think of the information from bruno-chareyre

I think you can completely trust Bruno's answer. I was not quite right, sorry.

You should definitely learn, how the contact law works, before using it.
Start with the simplest example with several spheres and test it.

Anton

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liucheng83 (lcheng83) said : 		#8

Thanks Anton Gladky, that solved my question.

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Nait (xuhero1989) said : 		#9

Hi, liucheng83

Have you got any answers about your question 1 and 2 now? I am facing some similar problem nowadays. Could you share some experience in dealing with the questions you listed here?

Nait