[CIG-LONG] Strain weakening non-newtonian rheology

[Walter Landry]

Marco Billia <maaubi at gmail.com> wrote:
> Hi Walter

Cc'ing the list.

> I would like to use a strain weakening non-newtonian rheology in Gale
> to simulate higher degrees of localization in the lower crustal part
> in my convergent indenter model. The idea is to initiate strain
> weakening after an "initialsofteningStrain" following a exponential
> strain softening curve to reach asymptotic behaviour at a defined
> deviatoric stress after a "finalsofteningStrain".
> Is there a possibility to directly define such a simple visco-plastic
> weakening function in the strain weakening or nonNewtonian component?
> The command lines of the stage I am at are attached below.

Strain weakening only works to modify the parameters of the
DruckerPrager rheology.  To make it modify the NonNewtonian rheology,
you would have to modify

  Underworld/Rheology/src/NonNewtonian.h
  Underworld/Rheology/src/NonNewtonian.cxx

Cheers,
Walter Landry

> Thank you for your efforts and for your time!
> 
> Kind Regards,
> Marco Billia
> 
> "strainWeakening_LC":
>         {
>             "Type": "StrainWeakening",
>             "TimeIntegrator": "timeIntegrator",
>             "MaterialPointsSwarm": "materialSwarm",
>             "initialsofteningStrain": "1.0",
>             "finalsofteningStrain": "5.0"
>         },
>         "nonNewtonian":
>         {
>             "Type": "NonNewtonian",
>             "StrainRateInvariantField": "StrainRateInvariantField",
>             "TemperatureField": "TemperatureField",
>             "StrainWeakening": "strainWeakening_LC",
>             "n": "3.0",
>             "T_0": "1.0",
>             "A": "1.0",
>             "refStrainRate": "0.01",
>             "minViscosity": "0.1",
>             "maxViscosity": "2.0"
>         },
>         "Hangingwall_viscous":
>         {
>             "Type": "RheologyMaterial",
>             "Shape": "Hangingwall",
>             "density": "1.0",
>             "alpha": "1.0",
>             "diffusivity": "0.1",
>             "heatingElements": [
>                 {
>                     "Q": "0",
>                     "lambda": "0"
>                 }
>             ],
>             "Rheology": [
>                 "nonNewtonian",
>                 "storeViscosity",
>                 "storeStress"
>             ]
>         },
> 
> 
> 
> ----------------------
> 
> Marco Billia
> Department of Geology
> University of Otago
> PO Box 56
> Dunedin 9054
> New Zealand
> 
> Mobile: +64 210 244 73 84
> E-mail: maaubi at gmail.com
>