yade-users team mailing list archive

[kan <nicessgg@xxxxxxxxx>]

Vaclav, Bruno

Thanks to both of you very much.
Then how about the convertion from the stress to the force on each particle,
where the stresses are from the boundary ?

kan


On 1/23/08, yade-users-request@xxxxxxxxxxxxxxxx <
yade-users-request@xxxxxxxxxxxxxxxx> wrote:
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> Today's Topics:
>
>   1. Re: How to get the micro-force from the macro-stress (kan)
>   2. Re: How to get the micro-force from the macro-stress
>      (Bruno Chareyre)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 22 Jan 2008 23:58:21 -0600
> From: kan <nicessgg@xxxxxxxxx>
> Subject: Re: [Yade-users] How to get the micro-force from the
>        macro-stress
> To: yade-users@xxxxxxxxxxxxxxxx
> Message-ID:
>        <45213f870801222158h940302xf6135f5e07117df6@xxxxxxxxxxxxxx>
> Content-Type: text/plain; charset="utf-8"
>
> Thank you, Vaclav,
>
> So the step for this is :
> during each timestep, the position of each particle/element keeps the
> same, so we can calculate the force brom the force-displacement
> relationship(in this case, the order does not affect the calculation since
> all the particle/elements do not move), after we get the forces, we use
> this
> forces to calculate the acceleration, and then the velocity(average
> velocity),  and then the movement/displacement in this timestep, and then
> update the position of each particle/element to new positions by add
> movement/displacement to current position. (until now, the calculation
> cycle
> of this timestep is completed)
> then go to next timestep by use the new positions of particles/elements as
> the current position to do the next calculation cycle.
>
> is my understanding right?
>
>
>
> Thanks again.
>
> Kan
>
>
>
> On 1/22/08, yade-users-request@xxxxxxxxxxxxxxxx
> <yade-users-request@xxxxxxxxxxxxxxxx>
> wrote:
> >
> > Send Yade-users mailing list submissions to
> >        yade-users@xxxxxxxxxxxxxxxx
> >
> > To subscribe or unsubscribe via the World Wide Web, visit
> >        https://lists.berlios.de/mailman/listinfo/yade-users
> > or, via email, send a message with subject or body 'help' to
> >        yade-users-request@xxxxxxxxxxxxxxxx
> >
> > You can reach the person managing the list at
> >        yade-users-owner@xxxxxxxxxxxxxxxx
> >
> > When replying, please edit your Subject line so it is more specific
> > than "Re: Contents of Yade-users digest..."
> >
> >
> > Today's Topics:
> >
> >   1. How to get the micro-force from the macro-stress (kan)
> >   2. Re: How to get the micro-force from the macro-stress
> >      (V?clav ?milauer)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Mon, 21 Jan 2008 13:29:54 -0600
> > From: kan <nicessgg@xxxxxxxxx>
> > Subject: [Yade-users] How to get the micro-force from the macro-stress
> > To: yade-users@xxxxxxxxxxxxxxxx
> > Message-ID:
> >        <45213f870801211129l171d2a5cs69da2382202961f8@xxxxxxxxxxxxxx>
> > Content-Type: text/plain; charset="utf-8"
> >
> > Hi, buddies,
> >
> > I have some questiones.
> > 1. how to get the micro-force from the macro-stress?
> > As we know,for most of current studies, the concept of stress is used to
> > describe the stress status. but when we look into the micro level, we
> have
> >
> > to convert the macro-stress to descrete force that applied at each
> > particle,
> > then how to do this convert?
> >
> > 2. what is the calculation process in each time step?
> > The problem is that, as see the relation ship below,
> > ___\|/____\|/___\|/________
> > 01---02---03---04---05---06...
> > |   \   |  /  |      |       |      | ...
> > 11---12---13---14---15---16...
> > |      |      |   /  |   \  |      |...
> > 21---22---23---24---25---26...
> > ...
> > ...
> > x1---x2---x3---x4---x5---x6...
> >
> > in which, the number is the ID of a particle,
> > and "--- " , "/" ,"\" and  "|" between the numbers mean there is a
> contact
> > between the particles
> > "\|/" means force.
> > assume the 01-02-03-04...is the upper bounday layer, and the force is
> > applied as shown "\|/".
> > when the calculation begins, we need to detecte the contact and update
> the
> >
> > position of each particles,
> > now my problem comes:
> > what is the procedure to calculation and update the particles'
> > information,
> > you know the force is from up layer, so the first layer
> ("01-02-03-04...")
> >
> > should be calculated, then the second layer,and then the third layer....
> > but
> > in DEM, the particle is independent to move, so after some time, some
> > particles in the first layer may move to the second layer and some
> > particles
> > in second layer may  move to the first layer(other other layer),then how
> > should I do in order to know which particle should be calculated and
> > updated
> > first and which should be done later in the same timestep?
> > For example,
> > 01 has contacting neighbors 02 and 11, in a same timestep, after we have
> > calculated 01's properties( velocity, position....), we should calculate
> > 02
> > first, then 03(the neighbor of 02), after the layer of 01-02-03...is
> done,
> >
> > then we can step to calculate the 11, which is to say, in a same
> timestep,
> > though 02 and 11 are both contacting neighbors of 01, we should
> calculate
> > 02, and 11 later though 02 and 11 are both affected because of teh
> > movement
> > of 01. so, how to indentify which particle should be calculated and
> update
> > first , and which should be later?
> > (because it is a dynamic process, so just use the order of  ID  is
> not  a
> > way to solve this)
> >
> > Hope I have described the problem 2 clearly,
> >
> > Need your help, thanks so much.
> >
> > Kan
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL:
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> https://lists.berlios.de/pipermail/yade-users/attachments/20080121/93495eff/attachment-0001.html
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Tue, 22 Jan 2008 09:20:53 +0100
> > From: V?clav ?milauer < eudoxos@xxxxxxxx>
> > Subject: Re: [Yade-users] How to get the micro-force from the
> >        macro-stress
> > To: yade-users@xxxxxxxxxxxxxxxx
> > Message-ID: <4795A765.9040403@xxxxxxxx>
> > Content-Type: text/plain; charset=UTF-8
> >
> >
> > > so, how to indentify which particle should be calculated and update
> > > first , and which should be later?
> > > (because it is a dynamic process, so just use the order of  ID  is
> > > not  a way to solve this)
> > The trick is that you have constant positions during the whole timestep,
> > you calculate forces from all contacts (order doesn't matter, elements
> > don't move during calculation) and then, before next timestep begins,
> > there is LeapFrogPositionIntegrator, that calculates displacements based
> > on velocity, inertia, applied forces, ... and moves elements to the new
> > position. Obviously, your timestep must be small enough so that you get
> > convergence.
> >
> > HTH, Vaclav
> >
> >
> >
> > ------------------------------
> >
> > _______________________________________________
> > Yade-users mailing list
> > Yade-users@xxxxxxxxxxxxxxxx
> > https://lists.berlios.de/mailman/listinfo/yade-users
> >
> >
> > End of Yade-users Digest, Vol 19, Issue 14
> > ******************************************
> >
> -------------- next part --------------
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> ------------------------------
>
> Message: 2
> Date: Wed, 23 Jan 2008 10:29:14 +0100
> From: Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>
> Subject: Re: [Yade-users] How to get the micro-force from the
>        macro-stress
> To: yade-users@xxxxxxxxxxxxxxxx
> Message-ID: <479708EA.3010204@xxxxxxxxxxx>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> kan a ?crit :
> > Thank you, Vaclav,
> >
> > So the step for this is :
> > during each timestep, the position of each particle/element keeps the
> > same, so we can calculate the force brom the force-displacement
> > relationship(in this case, the order does not affect the calculation
> > since all the particle/elements do not move), after we get the forces,
> > we use this forces to calculate the acceleration, and then the
> > velocity(average velocity),  and then the movement/displacement in
> > this timestep, and then update the position of each particle/element
> > to new positions by add movement/displacement to current position.
> > (until now, the calculation cycle of this timestep is completed)
> > then go to next timestep by use the new positions of
> > particles/elements as the current position to do the next calculation
> > cycle.
> >
> > is my understanding right?
>
> Exactly right. What you describe here is the centered second order
> finite diffence scheme (also called leap-frog), which is used in Yade.
> It is probably the most common (and most simple) scheme in DEM codes.
> Other schemes may be possible but are not implemented.
>
> Bruno
>
> >
> >
> >
> > Thanks again.
> >
> > Kan
> >
> >
> >
> > On 1/22/08, *yade-users-request@xxxxxxxxxxxxxxxx
> > <mailto:yade-users-request@xxxxxxxxxxxxxxxx>* <
> > yade-users-request@xxxxxxxxxxxxxxxx
> > <mailto:yade-users-request@xxxxxxxxxxxxxxxx>> wrote:
> >
> >     Send Yade-users mailing list submissions to
> >            yade-users@xxxxxxxxxxxxxxxx
> >     <mailto:yade-users@xxxxxxxxxxxxxxxx>
> >
> >     To subscribe or unsubscribe via the World Wide Web, visit
> >            https://lists.berlios.de/mailman/listinfo/yade-users
> >     or, via email, send a message with subject or body 'help' to
> >            yade-users-request@xxxxxxxxxxxxxxxx
> >     <mailto:yade-users-request@xxxxxxxxxxxxxxxx>
> >
> >     You can reach the person managing the list at
> >            yade-users-owner@xxxxxxxxxxxxxxxx
> >     <mailto:yade-users-owner@xxxxxxxxxxxxxxxx>
> >
> >     When replying, please edit your Subject line so it is more specific
> >     than "Re: Contents of Yade-users digest..."
> >
> >
> >     Today's Topics:
> >
> >       1. How to get the micro-force from the macro-stress (kan)
> >       2. Re: How to get the micro-force from the macro-stress
> >          (V?clav ?milauer)
> >
> >
> >
> ----------------------------------------------------------------------
> >
> >     Message: 1
> >     Date: Mon, 21 Jan 2008 13:29:54 -0600
> >     From: kan <nicessgg@xxxxxxxxx <mailto:nicessgg@xxxxxxxxx>>
> >     Subject: [Yade-users] How to get the micro-force from the
> >     macro-stress
> >     To: yade-users@xxxxxxxxxxxxxxxx <mailto:yade-users@xxxxxxxxxxxxxxxx>
> >     Message-ID:
> >            <
> >     45213f870801211129l171d2a5cs69da2382202961f8@xxxxxxxxxxxxxx
> >     <mailto:45213f870801211129l171d2a5cs69da2382202961f8@xxxxxxxxxxxxxx
> >>
> >     Content-Type: text/plain; charset="utf-8"
> >
> >     Hi, buddies,
> >
> >     I have some questiones.
> >     1. how to get the micro-force from the macro-stress?
> >     As we know,for most of current studies, the concept of stress is
> >     used to
> >     describe the stress status. but when we look into the micro level,
> >     we have
> >     to convert the macro-stress to descrete force that applied at each
> >     particle,
> >     then how to do this convert?
> >
> >     2. what is the calculation process in each time step?
> >     The problem is that, as see the relation ship below,
> >     ___\|/____\|/___\|/________
> >     01---02---03---04---05---06...
> >     |   \   |  /  |      |       |      | ...
> >     11---12---13---14---15---16...
> >     |      |      |   /  |   \  |      |...
> >     21---22---23---24---25---26...
> >     ...
> >     ...
> >     x1---x2---x3---x4---x5---x6...
> >
> >     in which, the number is the ID of a particle,
> >     and "--- " , "/" ,"\" and  "|" between the numbers mean there is a
> >     contact
> >     between the particles
> >     "\|/" means force.
> >     assume the 01-02-03-04...is the upper bounday layer, and the force
> is
> >     applied as shown "\|/".
> >     when the calculation begins, we need to detecte the contact and
> >     update the
> >     position of each particles,
> >     now my problem comes:
> >     what is the procedure to calculation and update the particles'
> >     information,
> >     you know the force is from up layer, so the first layer
> >     ("01-02-03-04...")
> >     should be calculated, then the second layer,and then the third
> >     layer.... but
> >     in DEM, the particle is independent to move, so after some time,
> some
> >     particles in the first layer may move to the second layer and some
> >     particles
> >     in second layer may  move to the first layer(other other
> >     layer),then how
> >     should I do in order to know which particle should be calculated
> >     and updated
> >     first and which should be done later in the same timestep?
> >     For example,
> >     01 has contacting neighbors 02 and 11, in a same timestep, after
> >     we have
> >     calculated 01's properties( velocity, position....), we should
> >     calculate 02
> >     first, then 03(the neighbor of 02), after the layer of
> >     01-02-03...is done,
> >     then we can step to calculate the 11, which is to say, in a same
> >     timestep,
> >     though 02 and 11 are both contacting neighbors of 01, we should
> >     calculate
> >     02, and 11 later though 02 and 11 are both affected because of teh
> >     movement
> >     of 01. so, how to indentify which particle should be calculated
> >     and update
> >     first , and which should be later?
> >     (because it is a dynamic process, so just use the order of  ID  is
> >     not  a
> >     way to solve this)
> >
> >     Hope I have described the problem 2 clearly,
> >
> >     Need your help, thanks so much.
> >
> >     Kan
> >     -------------- next part --------------
> >     An HTML attachment was scrubbed...
> >     URL:
> >
> https://lists.berlios.de/pipermail/yade-users/attachments/20080121/93495eff/attachment-0001.html
> >
> >     ------------------------------
> >
> >     Message: 2
> >     Date: Tue, 22 Jan 2008 09:20:53 +0100
> >     From: V?clav ?milauer < eudoxos@xxxxxxxx <mailto:eudoxos@xxxxxxxx>>
> >     Subject: Re: [Yade-users] How to get the micro-force from the
> >            macro-stress
> >     To: yade-users@xxxxxxxxxxxxxxxx <mailto:yade-users@xxxxxxxxxxxxxxxx>
> >     Message-ID: < 4795A765.9040403@xxxxxxxx
> >     <mailto:4795A765.9040403@xxxxxxxx>>
> >     Content-Type: text/plain; charset=UTF-8
> >
> >
> >     > so, how to indentify which particle should be calculated and
> update
> >     > first , and which should be later?
> >     > (because it is a dynamic process, so just use the order of  ID  is
> >     > not  a way to solve this)
> >     The trick is that you have constant positions during the whole
> >     timestep,
> >     you calculate forces from all contacts (order doesn't matter,
> elements
> >     don't move during calculation) and then, before next timestep
> begins,
> >     there is LeapFrogPositionIntegrator, that calculates displacements
> >     based
> >     on velocity, inertia, applied forces, ... and moves elements to
> >     the new
> >     position. Obviously, your timestep must be small enough so that
> >     you get
> >     convergence.
> >
> >     HTH, Vaclav
> >
> >
> >
> >     ------------------------------
> >
> >     _______________________________________________
> >     Yade-users mailing list
> >     Yade-users@xxxxxxxxxxxxxxxx <mailto:Yade-users@xxxxxxxxxxxxxxxx>
> >     https://lists.berlios.de/mailman/listinfo/yade-users
> >     <https://lists.berlios.de/mailman/listinfo/yade-users>
> >
> >
> >     End of Yade-users Digest, Vol 19, Issue 14
> >     ******************************************
> >
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > Yade-users mailing list
> > Yade-users@xxxxxxxxxxxxxxxx
> > https://lists.berlios.de/mailman/listinfo/yade-users
> >
>
>
> --
>
> _______________
> Chareyre Bruno
> Maitre de conference
>
> Institut National Polytechnique de Grenoble
> Laboratoire 3S (Soils Solids Structures) - bureau E145
> BP 53 - 38041, Grenoble cedex 9 - France
> T?l : 33 4 56 52 86 21
> Fax : 33 4 76 82 70 43
> ________________
>
>
>
> ------------------------------
>
> _______________________________________________
> Yade-users mailing list
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>
>
> End of Yade-users Digest, Vol 19, Issue 15
> ******************************************
>

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