Problem with Drucker Prager material

[mnt]

Hi.
I create a simple model with Drucker Prager material and quad elements but it didn't converge at all even in static analysis.
I try my model with other materials like PDMY and it runs without any problem.
I also change any parameters of this material but in didn't converge.
What is wrong with this material? Does it work correctly?

[fmk]

the material does work and does work correctly. why don't you post the command you used.

[siddharthfcb]

I used the following to simulate triaxial test on a 8 node brick element. But the response that I get is purely elastic and no hardening is observed in the output even if I vary kinf and ko by any amount. Please help .. Thanks



wipe
model BasicBuilder -ndm 3 -ndf 3
#--create the nodes
node 1 1.0 0.0 0.0
node 2 1.0 1.0 0.0
node 3 0.0 1.0 0.0
node 4 0.0 0.0 0.0
node 5 1.0 0.0 1.0
node 6 1.0 1.0 1.0
node 7 0.0 1.0 1.0
node 8 0.0 0.0 1.0
#set triaxial test boundary conditions
fix 1 0 1 1
fix 2 0 0 1
fix 3 1 0 1
fix 4 1 1 1
fix 5 0 1 0
fix 6 0 0 0
fix 7 1 0 0
fix 8 1 1 0


#--define material parameters for the model
#---bulk modulus
set k 27777.78
#---shear modulus
set G 9259.26
#---yield stress
set sigY 5.0
#---failure surface and associativity
set rho 0.398
set rhoBar 1.5
#---isotropic hardening
set Kinf 2
set Ko 21.0
set delta1 3.0
#---kinematic hardening
set H 0.0
set theta 1.0
#---tension softening
set delta2 0.0
#---mass density
set mDen 1.7

#--material models
# type tag k G sigY rho rhoBar Kinf Ko delta1 delta2 H theta density
nDMaterial DruckerPrager 2 $k $G $sigY $rho $rhoBar $Kinf $Ko $delta1 $delta2 $H $theta $mDen


#element
element stdBrick 1 1 2 3 4 5 6 7 8 2 0.0 0.0 0.0
puts "model Built.."

set p 0.5
set q 0.5
set pNode [expr -$p/4]
set qNode [expr -$q/4]
#--loading object for hydrostatic pressure

set Time 0.0
wipeAnalysis
pattern Plain 1 Constant {
load 1 $pNode 0.0 0.0
load 2 $pNode $pNode 0.0
load 3 0.0 $pNode 0.0
load 5 $pNode 0.0 $pNode
load 6 $pNode $pNode $pNode
load 7 0.0 $pNode $pNode
load 8 0.0 0.0 $pNode
}

integrator LoadControl 0.1
numberer RCM
system SparseGeneral
constraints Transformation
test NormDispIncr 1e-5 10 1
algorithm Newton
analysis Static
analyze 10


#--loading object deviator stress
pattern Plain 2 Linear {
load 5 0.0 0.0 $qNode
load 6 0.0 0.0 $qNode
load 7 0.0 0.0 $qNode
load 8 0.0 0.0 $qNode
}

#-------------------------------------------------------
# create the analysis
#-------------------------------------------------------
#record nodal displacements

recorder Node -file displacementsDPiso.txt -time -nodeRange 1 8 -dof 1 2 3 disp
# record element displacements
recorder Element -ele 1 -time -file stress1DPiso.txt -dT 0.001 material 2 stress
recorder Element -ele 1 -time -file strain1DPiso.txt -dT 0.001 material 2 strain
recorder Element -ele 1 -time -file stateDPiso.txt -dT 0.001 material 2 state
recorder Element -ele 1 -time -file LoadDPiso.txt -dT 0.001 material 2 globalForce
record

puts "recorders set"

integrator LoadControl 0.01
numberer RCM
system SparseGeneral
constraints Transformation
test NormDispIncr 1e-5 10 1
algorithm Newton
analysis Static
analyze 105000

puts "triaxial shear application finished..."