[CIG-SHORT] Kelvin-Voigt viscoelasticity

[Charles Williams]

Dear Satoshi,

I have not been through your e-mail in detail, but I am attaching an e-mail from Eric Hetland from about a year ago that may be of use to you.  You are correct that it is not possible to specify shear-ratio as a value greater than one.  The solution is to use a large value for the overall shear modulus, and then assign the ratios appropriately.  Please let us know if you require additional assistance.

Cheers,
Charles


> Begin forwarded message:
> 
> From: Eric Hetland <ehetland at umich.edu>
> Subject: Re: [CIG-SHORT] Fwd: rheology model in pylith
> Date: 31 January 2015 at 5:28:39 AM NZDT
> To: cig-short at geodynamics.org
> Cc: Charles Williams <C.Williams at gns.cri.nz>, "Liu, Zhen \(3242\)" <Zhen.Liu at jpl.nasa.gov>
> Reply-To: cig-short at geodynamics.org
> 
> 
> As it is, I am covering this in a class right now. Attached is a document I use deriving the equivalence of the parameters in either a general Maxwell or Kelvin. There are some checks on the derivations, so I think it is correct, but please let me know if it doesn't seem like its working...
> 
> 
> 
> On Fri, Jan 30, 2015 at 10:59 AM, Brad Aagaard <baagaard at usgs.gov <mailto:baagaard at usgs.gov>> wrote:
> Zhen,
> 
> Charles Williams is more familiar with how to setup the generalized Maxwell model to match some common viscoelastic rheologies than I am. I am reposting this question to cig-short and cc'ing Charles.
> 
> Brad
> 
> 
> 
> -------- Forwarded Message --------
> Subject:        rheology model in pylith
> Date:   Fri, 30 Jan 2015 02:15:43 +0000
> From:   Liu, Zhen (329A) <Zhen.Liu at jpl.nasa.gov <mailto:Zhen.Liu at jpl.nasa.gov>>
> To:     baagaard at usgs.gov <mailto:baagaard at usgs.gov> <baagaard at usgs.gov <mailto:baagaard at usgs.gov>>
> 
> 
> 
> Hi Brad,
> 
> How are you? We have email communication before about CIG workshop. At
> present I am looking into the Pylith to see if I can use it in my
> research. I notice that current pylith has Bulk rheology models
> including Elastic model, Linear Maxwell viscoelastic models, Generalized
> Maxwell viscoelastic models, Power-law viscoelastic model,
> Drucker-Prager elastoplastic model. I am interested in adopting
> bi-viscous Burgers rheology, which is the Kelvin-voigt plus maxwell
> rheology in series. Do you know if this is something already in Pylith
> or need to be implemented?
> 
> I understand that Kelvin-voigt and Maxwell rheology can be represented
> as special case from generalized maxwell viscoelastic models. But it is
> less clear to me how to represent the Burgers theology from the
> generalized maxwell model (or not). Your any insight would be much
> appreciated!
> 
> Thanks in advance for the help,
> 
> Best regards,
> Zhen
> -----------------------------------------------
> 
> Dr. Zhen Liu
> 
> Jet Propulsion Laboratory, M/S 300-233
> 
> California Institute of Technology
> 
> 4800 Oak Grove Drive
> 
> Pasadena, CA 91109
> 
> Ph: 818-393-7506 <tel:818-393-7506>
> 
> fax: 818-354-9476 <tel:818-354-9476>
> 
> email: zhen.liu at jpl.nasa.gov <mailto:zhen.liu at jpl.nasa.gov>
> 
> 
> 
> 
> 
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> 
> 
> -- 
> ---------------------------------------------------------------
> 
> Eric Hetland
> 
> Assistant Professor
> 
> Department of Earth & Environmental Sciences
> 
> 3008 CC Little Bldg
> 
> 1100 N University Ave
> 
> Ann Arbor, MI 48103, USA
> 
> ehetland at umich.edu <mailto:ehetland at umich.edu>
> www.earth.lsa.umich.edu/~ehetland <http://www.earth.lsa.umich.edu/~ehetland>_______________________________________________
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Charles A. Williams
Scientist
GNS Science
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C.Williams at gns.cri.nz <mailto:C.Williams at gns.cri.nz>

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