[CIG-SHORT] plastic deformation
Birendra jha
bjha7333 at yahoo.com
Mon Dec 1 13:26:48 PST 2014
Thanks Charles and Brad for your suggestions.
Yes, it appears we need to store stress state from previous time step to implement the incremental formulation of these models.
Yes, it is additive decomposition of strain into elastic and plastic parts.
Thanks
Birendra
--------------------------------------------
On Mon, 12/1/14, Charles Williams <willic3 at gmail.com> wrote:
Subject: Re: [CIG-SHORT] plastic deformation
To: "Birendra jha" <bjha7333 at yahoo.com>
Cc: "cig-short" <cig-short at geodynamics.org>
Date: Monday, December 1, 2014, 4:13 PM
Does this mean we would need to save
the stresses from the previous time step?
Charles
> On 2/12/2014, at 6:50 am, Birendra jha <bjha7333 at yahoo.com>
wrote:
>
> Another important question:
>
> 4. Stress integration in pylith's DruckerPrager is
implemented based on two points in time: the initial time
and the current estimate at the current time. Do you think
we need to integrate from the previous time step, if we
implement camclay type models?
>
> Thanks
> Birendra
> --------------------------------------------
> On Mon, 12/1/14, Birendra jha <bjha7333 at yahoo.com>
wrote:
>
> Subject: Re: [CIG-SHORT] plastic deformation
> To: "Charles Williams" <willic3 at gmail.com>
> Date: Monday, December 1, 2014, 11:58 AM
>
> Hello Charles
>
> I am implementing the Modified Cam Clay model into
Pylith
> following the paper: Cam-Clay plasticity, Part I
Implicit
> Integration of elasto-plastic constitutive relations,
Borja
> and Lee, CMAME, 1990
>
> 1. Can I start by copying the DruckerPrager3D files
and
> modify the yield function (yieldFunction), calculation
of
> plastic strain, and calculation of consistent tangent
> (elasticConsts)? The relevant functions are
> _calcStressElastoplastic,
_calcElasticConstsElastoplastic,
> _updateStateVarsElastoplastic.
>
> 2. Is this a good idea to implement the rate-dependent
> plasticity (e.g. camclay) using the pylith formulation?
I
> mean, solve for the consistency parameter separately
(in an
> inner Newton loop for cam clay), and for displacement
or
> total strain in the outer Newton loop? The consistency
> parameter for this non-associative camclay model is
the
> volumetric plastic strain itself.
>
> 3. Can you recommend another source for the Modified
Cam
> Clay implementation? I already found couple of typos in
the
> above paper.
>
> As I am debugging poor convergence of the nonlinear
solver,
> I want to get your expert opinion regarding this.
>
> Thanks and best regards
> Birendra
>
>
> --------------------------------------------
> On Mon, 10/6/14, Charles Williams <willic3 at gmail.com>
> wrote:
>
> Subject: Re: [CIG-SHORT] plastic deformation
> To: "Birendra jha" <bjha7333 at yahoo.com>
> Date: Monday, October 6, 2014, 5:15 PM
>
> Thanks, Birendra. This
> looks interesting, and it may be worth putting
into PyLith
> at some point.
>
> Cheers,
> Charles
>
>
> On 7/10/2014, at 10:06 am, Birendra jha <bjha7333 at yahoo.com>
> wrote:
>
>> I have attached
> the paper.
>>
>>
>>
> --------------------------------------------
>> On Mon, 10/6/14, Charles Williams <willic3 at gmail.com>
> wrote:
>>
>> Subject:
> Re: [CIG-SHORT] plastic deformation
>> To:
> cig-short at geodynamics.org
>> Date: Monday, October 6, 2014, 3:07 PM
>>
>> Hi Birendra,
>>
>>
>> On 6/10/2014,
>> at 5:43
> pm, Birendra jha <bjha7333 at yahoo.com>
>> wrote:
>>
>>> Hi Charles
>>>
>
>>> Thank you very much.
>> That is very helpful.
>>>
>>> Eq.(5.113):
> Yes, cohesion c should not be
>> there and
> the missing term is 3*\alpha_f*P^I.
>>
>> Yes, that is what I have.
>>
>>>
>>> Can
>> you please
> confirm that derivative of d w.r.t epsilon i.e.
>> Eqs.(5.123), with (5.124), is correct?
>>
>> I have not reworked
> this equation, but it
>> should be
> correct. If you derive it yourself from
equation
>> 111, keep in mind that there is a factor
> of 2 involved for
>> off-diagonal terms
> depending on whether you are using the
>>
> tensor form or the vectorized equivalent of the
>> stress/strain tensors.
>>
>>>
>>
>>> Eq.(5.117):
> Should P^I be multiplied
>> with R_i as
> well? Although, this won't change the
>> tangent matrix.
>>
>> Yes. I
>> think I left
> it out because I knew it wouldn’t affect the
>> tangent matrix, but I am making these
> corrections in the
>> manual.
>>
>>
>>>
>>> I saw a
> recent paper
>> (A new exact integration
> method for the Drucker–Prager
>>
> elastoplastic model with linear isotropic
hardening,
>>> László Szabó and Attila Kossa, Int
> J
>> Solids Structures, 2012) that looks
> useful because it has
>> exact expressions
> for tangent matrix.
>>>
>> What do you think about these methods?
>>
>> I haven’t looked
> at this, but I will try to
>> have a
> look. We don’t have that journal here at
GNS.
>>
>> Cheers,
>> Charles
>>
>>
>>
>>>
>>>
>> Thanks again
>>>
> Birendra
>>>
>>
> --------------------------------------------
>>> On Sun, 10/5/14, Charles Williams
> <willic3 at gmail.com>
>> wrote:
>>>
>>> Subject:
>> Re:
> [CIG-SHORT] plastic deformation
>>>
> To:
>> cig-short at geodynamics.org
>>> Date: Sunday, October 5, 2014, 4:41
> PM
>>>
>>> Hi
> Birendra,
>>>
>>>
> Probably the best
>> reference
>>> for the Drucker-Prager stuff
>> is the finite element book by
>>> Bathe
>> (Finite
> Element Procedures, 1995). Also, much of
the
>>> solution method for Drucker-Prager
>> elastoplastic materials
>>> is analogous to
>>
> the procedure for power-law viscoelastic
>>> materials.
>>>
>
>>> 1. Equation
>>> 5.104
>> is just
> isolating the elastic deformation component,
>>> so that the stress can be computed
> by
>> operating on the
>>> elastic strain. We
>> divide this into deviatoric and
>>>
>> volumetric
> components, which makes things easier.
>>>
>>> 2. What we
> mean
>> here is
>>>
> taking the scalar inner product
>>
> (defined at the beginning of
>>>
> section
>> 5.3.1).
>>>
>>> 3.
>> The
>>> cohesion
> appears to be a typo (I
>> actually think
> it is left
>>> over from an
>> older derivation). In going through
> this,
>>> however, I believe I
> discovered a missing
>> factor of 3 *
> P^I
>>> in this equation. I
>> will need to double-check this and see
>>>
>> if this is
> correct. If you have derived this equation
>>> separately, I would appreciate
>> confirmation.
>>>
>>>
>> 4. Are you
> referring to the
>>> split
>> into elastic and plastic parts? The
> additive
>>> decomposition is
> frequently used, although
>> I have also
> seen
>>> a multiplicative
>> decomposition (see the book referred to
>>>
>> above).
>>>
>>>
>> Cheers,
>>>
> Charles
>>>
>>
>>>
>>> On
> 5/10/2014, at
>> 1:20 pm, Birendra jha
> <bjha7333 at yahoo.com>
>>> wrote:
>>>
>>>> Hi
>>>
>> developers/users,
>>>>
>>>>
>>> I am trying to
>>
> understand Sec 5.4.2.1 Drucker-Prager
>>>
>> Elastoplastic
> With No Hardening (Perfectly Plastic). Can
>> you
>>> please point
> me to a paper/document
>> which describes
> this
>>> formulation? For
>> example,
>>>>
>>>>
>> 1. What is
> the basis of Eq.(5.104), first
>>>
> equality? Can we write this for general
>>
> loading?
>>>>
>>>>
>> 2. What is
> the
>>> meaning of "taking
>> the scalar product of both
>>> sides",
>>
> above Eq.(5.109). I can derive lambda by
>>> multiplying Eq.(5.100) on both sides
> by
>> df/dsigma : C^E. But
>>> this lamda does
>>
> not quite look like (5.109) because of
>>>
>> (5.104). also, I
> would like to understand d in Eq(5.110).
>>>>
>>>> 3. I
> am not
>> able to
>>>
> derive the term in the bracket
>> in
> Eq.(113). How does
>>> cohesion
> enter
>> here?
>>>>
>>>>
> 4.
>> Eq.(5.117): what is the basis of
> this
>>>
>> split?
> Is it always valid?
>>>>
>>>> I'd just like to understand
> the
>>> formulation.
>>>>
>>>>
>>> Thanks for any
>>
> help
>>>> Birendra
>>>>
>>>>
>>>
>>
> --------------------------------------------
>>>> On Thu, 10/2/14, Brad Aagaard
> <baagaard at usgs.gov>
>>> wrote:
>>>>
>
>>>> Subject:
>>> Re:
>> [CIG-SHORT]
> plastic deformation
>>>>
>> To:
>>> cig-short at geodynamics.org
>>>> Date: Thursday, October 2,
> 2014,
>> 10:50
>>>
> AM
>>>>
>>>> Birendra,
>>>>
>>>> It
> would help to
>>>
>>
> know what you
>>>> have tried to
>> resolve
>>> this
> problem? Have
>>>> you checked
> the
>>>
>> scales
> used in the
>>>>
>>> nondimensionalization? Have you
>>>>
>>>
> verified
>>>> convergence for the
> same
>>> problem with a linear elastic
>
>>>>
>>>
> material? Does a
>> linear elastic
> material
>>>> converge in
>> one nonlinear solve
>>>> iteration?
>>>> What else
>>>
> have
>> you tried?
>>>>
>>>>
>>> Regards,
>>>>
> Brad
>>>>
>>>>
>>>> On
> 10/2/14,
>> 6:39
>>>
> AM,
>>>>
>>
> Birendra jha wrote:
>>>>> Hi
>>>>>
>>>>> I am
>>
> trying to run a
>>>> plastic
> deformation
>> case with the
>>> DruckerPrager3D
>>
> material.
>>>> The nonlinear
>>> solver does not converge. Attached
> are
>> my
>>>>
> files, which run.
>>>>>
>>>
>>>>>
>>>> It's
>> a
>>> very small setup: 10x1x1 column,
>> loaded at one
>>>>
> end with a cyclic
>> load that leads to
>>> compression and
>>
> tension
>>>> in the column
>>> in a sinusoidal manner.
>>>>> I
>>>>
> want to
>> compare the plastic strain
> output
>>> with
>> my
> analytical
>>>> solution.
>>>>>
>>>>>
>> Can
>>>> someone please take a look and
>> help me
>>> with the
> convergence
>>>> issue?
>>>>>
>>
>>>>> Thanks
>>>>> Birendra
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>
>>>
>>
> _______________________________________________
>>>>> CIG-SHORT mailing list
>>>>> CIG-SHORT at geodynamics.org
>>>>> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>>>>>
>>>>
>
>>>>
>>>
>>
> _______________________________________________
>>>> CIG-SHORT mailing list
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>>>>
>>>>
>>>
>>
> _______________________________________________
>>>> CIG-SHORT mailing list
>>>> CIG-SHORT at geodynamics.org
>>>> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>>>
>>> Charles
> A.
>> Williams
>>>
> Scientist
>>>
>> GNS
> Science
>>> 1 Fairway Drive, Avalon
>>> PO Box
>>>
> 30368
>>> Lower Hutt 5040
>>>
>> New
>>> Zealand
>>> ph
>> (office): 0064-4570-4566
>>> fax (office):
>>
> 0064-4570-4600
>>> C.Williams at gns.cri.nz
>>>
>>
>>>
>>
> _______________________________________________
>>> CIG-SHORT mailing list
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>>>
>>>
>>
> _______________________________________________
>>> CIG-SHORT mailing list
>>> CIG-SHORT at geodynamics.org
>>> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>>
>> Charles A.
> Williams
>> Scientist
>>
> GNS Science
>> 1 Fairway Drive, Avalon
>> PO Box
>> 30368
>> Lower Hutt 5040
>>
> New
>> Zealand
>> ph
> (office): 0064-4570-4566
>> fax (office):
> 0064-4570-4600
>> C.Williams at gns.cri.nz
>>
>>
> _______________________________________________
>> CIG-SHORT mailing list
>> CIG-SHORT at geodynamics.org
>> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short<Szabo_druckerprager_IJSS2012.pdf>
>
> Charles A. Williams
> Scientist
> GNS Science
> 1 Fairway Drive, Avalon
> PO Box
> 30368
> Lower Hutt 5040
> New
> Zealand
> ph (office): 0064-4570-4566
> fax (office): 0064-4570-4600
> C.Williams at gns.cri.nz
>
Charles A. Williams
Scientist
GNS Science
1 Fairway Drive, Avalon
PO Box 30368
Lower Hutt 5040
New Zealand
ph (office): 0064-4570-4566
fax (office): 0064-4570-4600
C.Williams at gns.cri.nz
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