Re: [Yade-users] [Question #263739]: isotropic compression at controled pressure
Question #263739 on Yade changed: https://answers.launchpad.net/yade/+question/263739 Status: Answered = Open Luc OGER is still having a problem: I made several tests to see if putting some max_vel solved my problem, it seems that it is not what I was expected. but to understand more my queston, I have to described what I was looking for : I want to look at the consequence at the anisotropy linked to the gravity deposition process. So my first step is doing a packing from spheres distributed randmoly inside big vertical box , letting them settling down, (in order to get a quasi cubic dense packing) putting the top wall at the upper point of the packing and then doing an isotropic compression by pressure control on all the walls but one by one. Indeed, the top wall starts with zero pressure and has to move alone to reach some pressure similar to the mean values of the others before moving the other walls. Otherwise I will reorganise too much the structure before compressing. i hope my description is clear enough for the understanding. -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #263739]: isotropic compression at controled pressure
Question #263739 on Yade changed: https://answers.launchpad.net/yade/+question/263739 Status: Open = Answered Bruno Chareyre proposed the following answer: Hello, I don't understand exactly in which sense it is not what you expect. I suggest to forget max_vel, assign a very large value to it so that it does not interfere. Trying to summarize what to do in your case (assuming TriaxialStressCOntroller is labeled triax): #stress control in all directions and for all boundaries independently triax.stressMask = 7 triax.internalCompaction=False # if there is gravity, imposing the same stress at the top and bottom boundaries would lead to free fall... block the bottom wall: triax.wall_bottom_activated=False #define the target stresses to be applied, if it must be isotropic: triax.goal1=triax.goal2=triax.goal3=isoP #then run O.run() This will reach the target isoP very quickly (a few iterations), in fact it could well result in a dynamic compaction at constant applied pressure (exception is if you impose a small max_vel). If what you want is to increase the isotropic confinement progressively: for k in range(N): triax.goal1=triax.goal2=triax.goal3=isoP*float(k)/float(N) O.run(number,True) The problem is the initial stress under gravity is not isotropic, for superimposing an isotropic stress to the intitial anisotropic one, better something like this: #initialize with current stress triax.goal1=triax.stress(0)[0] triax.goal2=-triax.stress(3)[1] triax.goal3=triax.stress(4)[2] #and increase progressively for k in range(N): triax.goal1+= isoP/float(N) triax.goal2+= isoP/float(N) triax.goal3+= isoP/float(N) O.run(number,True) Bruno -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #263739]: isotropic compression at controled pressure
Question #263739 on Yade changed: https://answers.launchpad.net/yade/+question/263739 Status: Answered = Open Luc OGER is still having a problem: thanks for the fast reply. I don't want to reach quickly the isotropic goal as some local reorganisaiton for the contacts between spheres is part of my studies, indeed the particles are frictionless which allow rotations and sliding during the slow compression process. so I guess that this solution (copy from your answer) will be the good one coupled with a small max_vel if the change of the triaxgoal loop only occurs when it is reached ?: Number effect is unclear for me in this example : If what you want is to increase the isotropic confinement progressively: for k in range(N): triax.goal1=triax.goal2=triax.goal3=isoP*float(k)/float(N) O.run(number,True) -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #263739]: isotropic compression at controled pressure
Question #263739 on Yade changed: https://answers.launchpad.net/yade/+question/263739 Status: Open = Answered Bruno Chareyre proposed the following answer: coupled with a small max_vel No need I think. For very smooth evolutions select a large N (10e4 or so), in which case number can be 1 (the number of iterations between each change of the applied pressure). Depends how close to equilibrium you want to be (it will need a bit of trial-error probably). In my experience there is an overhead when writing: for k in range(100): O.run(1,1) which makes things slower compared to (for instance) for k in range(10): O.run(10,1) That would be the only reason to use larger stress steps with more iterations between them. -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #263739]: isotropic compression at controled pressure
Question #263739 on Yade changed: https://answers.launchpad.net/yade/+question/263739 Status: Open = Answered Luc Sibille proposed the following answer: Hello Luc, Yes it is possible. You can find a detailed example about how to use TriaxialStresscontroller here: http://bazaar.launchpad.net/~yade-pkg/yade/git-trunk/view/head:/examples/triax-tutorial/script-session1.py to control the pressure on all the walls you have do define the arguments: stressMask = 7 and goal1=goal2=goal3=the pressure that you want to (with a minus sign for a compressive pressure). Cheers, Luc Le Lundi 16 Mars 2015 17:16 CET, Luc OGER question263...@answers.launchpad.net a écrit: New question #263739 on Yade: https://answers.launchpad.net/yade/+question/263739 I am new in the use of Yade and it is not clear for me how to define some parameters for the TriaxialStresscontroller class in order to make a triaxial compression with identical pressures in all the walls. In my understanding of the class I can controled the strain rate and/or the wall displacements but not the pressure on all the walls to have the same value during the isotropic compression. so my question : is it possible ? and if yes how I can do that? thanks in advance. -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp -- Luc Sibille Université Joseph Fourier / IUT1 de Grenoble Laboratoire 3SR UMR CNRS Tel lab.: +33 (0)4 76 82 63 48 Tel IUT: +33 (0)4 76 82 53 36 You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
[Yade-users] [Question #263739]: isotropic compression at controled pressure
New question #263739 on Yade: https://answers.launchpad.net/yade/+question/263739 I am new in the use of Yade and it is not clear for me how to define some parameters for the TriaxialStresscontroller class in order to make a triaxial compression with identical pressures in all the walls. In my understanding of the class I can controled the strain rate and/or the wall displacements but not the pressure on all the walls to have the same value during the isotropic compression. so my question : is it possible ? and if yes how I can do that? thanks in advance. -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #263739]: isotropic compression at controled pressure
Question #263739 on Yade changed: https://answers.launchpad.net/yade/+question/263739 Status: Answered = Open Luc OGER is still having a problem: Luc Thanks for the fast answer but this example is not exactly that I was expecting : I want to compress by the walls not by growxing the spheres and as the time to get equilibrium when moving the walls is crucial I want to select the rate to this iso-compression. if I understand mask=7 and all goal identical are more linked to final results not to the progressive intermediate steps. Luc -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #263739]: isotropic compression at controled pressure
Question #263739 on Yade changed: https://answers.launchpad.net/yade/+question/263739 Status: Open = Answered Jérôme Duriez proposed the following answer: Performing isotropic compression moving the walls at a constant rate is still possible: you just have to switch internalCompaction to false (*) (it is true by default) As for the rate part, using stressMask = 7, the appropriate attribute to set is max_vel (**). Basically, for stress controlled behavior of TriaxialStressController, this engine tries, moving the walls with internalCompaction=0, to reach the desired stress value in one iteration. But, without exceeding a wall velocity of max_vel... Then, if you want to iso-compress your sample to some pressure significantly different from the initial one, just use stressMask=7, internalCompaction=0, and max_vel=someValue, and you will perform an isotropic compression at a constant strain rate corresponding to someValue From my point of view, there is no reason to consider all these attributes related to final results rather than intermediate steps. (*) https://yade-dem.org/doc/yade.wrapper.html?highlight=triaxialstress#yade.wrapper.TriaxialStressController.internalCompaction (**) https://yade-dem.org/doc/yade.wrapper.html?highlight=triaxialstress#yade.wrapper.TriaxialStressController.max_vel -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
