[CIG-SHORT] "Runtimeerror Infeasible stress state" - cannot project back to yield surface.

[Brad Aagaard]

What initial stress conditions are you using? The algorithm will have 
difficulty when there is a significant step in deviatoric strain while 
under small confining pressure.

Regards,
Brad

On 05/14/2014 09:49 PM, Ma, Xiao wrote:
> Hi,
> I am running a simulation using Druckerprager elstoplastic model, when I run the code, I get the following error
> "Runtimeerror Infeasible stress state" - cannot project back to yield surface.
> Here is how I wrote the plastic material part :
>
>
> [pylithapp.timedependent]
>
> materials = [plastic]
>
> [pylithapp.timedependent.materials]
>
>
>
> elastic = pylith.materials.DruckerPragerPlaneStrain
>
>
> [pylithapp.timedependent.materials.plastic]
>
>
> # Label for material
>
> label = Plastic material
>
>
> # Nodeset id from CUBIT
>
> id = 1
>
>
> # Spatial database with physical properties for elastic material
>
> db_properties.label =Plastic properties
>
> db_properties.iohandler.filename = matprops.spatialdb
>
>
> # Set the basis functions and quadrature:
>
> # 2-D Lagrange cell with 2nd order quadrature
>
> quadrature.cell = pylith.feassemble.FIATLagrange
>
> quadrature.cell.dimension = 2
>
> quadrature.cell.quad_order = 2
>
> ************************************
>
> And This is the material database I am using .
>
> #SPATIAL.ascii 1
>
> SimpleDB {
>
> // number of physical properties
>
> num-values = 6
>
>
> // Names and units of physical properties
>
> value-names = density vs vp friction-angle cohesion dilatation-angle // names of the material property values
>
> value-units = kg/m**3 m/s m/s degree kPa degree // units
>
>
> // Number of locations where physical properties are given
>
> // 1 location -> data is uniform -> data dimension is 0
>
> num-locs = 1
>
> data-dim = 0
>
>
> // Problem is in 2-D
>
> space-dim = 2
>
>
> // Coordinate system (2-D with coordinates in meters)
>
> cs-data = cartesian {
>
> to-meters = 1.0
>
> space-dim = 2
>
> }
>
> }
>
> // Columns are x, y, density, vs, vp
>
> 0.0 0.0 2500.0 3000.0 5291.502622129181 30.0 50.0 30.0
>
>
> Best,
>
> XIao
>
>
>
>
>
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