stress or strain recorder for shell element

[tusharkantimandal]

Hi all,
I am using "ShellMITC4" element with nDmaterial "Drucker Prager". The node recorder are working properly..giving the nodal displacements. But I want to record the stress and strain. The recorder files are showing only time step values without any stress or strain value. Actually the stress/strain recorders are giving values for the brick element properly.
Q1:: one example on "strain recorder for ShellMITC4" element.
Q2:: what -dT means in the stress/strain recorder?
### My code###
# all dimensions are in meter and kg, N, m
wipe; #to wipe out previously done works: generated model etc.
set P 1000;#Amplitude....
set output out_t;
file mkdir $output
set C C;
puts "modelling is starting"
model BasicBuilder -ndm 3 -ndf 6
set mon_dof 1;
set mon_node 3;
set maxU -0.1;#max limiting displacement
set dUmin -0.0001; # Displacement increment
set dUmax -0.1;
set dU -0.001
set startT [clock seconds]
#--define material parameters for the model
set mf_E [expr 1*1.92*1.003*0.9973];
set mf_fy [expr 1*2.951];
#---bulk modulus
set k [expr $mf_E*17570];
#---shear modulus
set G [expr $mf_E*13170];
#---yield stress
set sigY [expr $mf_fy*3.78];
#---failure surface and associativity
set rho 0.350
set rhoBar 0.350
#---isotropic hardening
set Kinf 0.0
set Ko 0.0
set delta1 0.0
#---kinematic hardening
set H 0.0
set theta 1.0
#---tension softening
set delta2 0.0
#---mass density
set mDen 0.002500;#in kg/mm^3
#--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
#nDMaterial PlateFiber $matTag $threeDTag
nDMaterial PlateFiber 3 2
set h 5;#thickness
set B 5;#width
set L 100;#length
#section PlateFiber $secTag $fiberTag $h
section PlateFiber 1 3 $h
#node nodeTag x Y z
node 1 0.000 0.000 0.0
node 2 0.000 $B 0.0
node 3 $L $B 0.0
node 4 $L 0.000 0.0
# fix the end nodes
fix 1 1 1 1 1 1 1
fix 2 1 1 1 1 1 1
fix 3 0 1 1 1 1 1
fix 4 0 1 1 1 1 1
equalDOF 3 4 1;
#element ShellMITC4 eleTag iNode jNode kNode lNode secTag
element ShellMITC4 1 1 2 3 4 1
#define damping
#set xDamp 0.05; # damping ratio
#source eig_analysis.tcl;
#Ref load...
set patternTag 1;
pattern Plain $patternTag Linear {
# Create nodal loads at node 2
# nd FX FY MZ
load 3 $P 0.0 0.0 0.0 0.0 0.0
load 4 $P 0.0 0.0 0.0 0.0 0.0
}
#recorder
set step 0.1
recorder Node -file $output/disp$mon_node$C.out -time -node $mon_node -dof $mon_dof disp;

# record the element stress, strain, and state at one of the Gauss points
recorder Element -ele 1 -time -file $output/stress1.out material 3 stress
recorder Element -ele 1 -time -file $output/strain1.out material 3 strain
recorder Element -ele 1 -time -file $output/state1.out material 3 state

##### Transient analysis###
wipeAnalysis;
#analysis objects....
# Create the system of equation, a sparse solver with partial pivoting
system BandGeneral

# Create the constraint handler, the transformation method
constraints Transformation

# Create the DOF numberer, the reverse Cuthill-McKee algorithm
numberer RCM

# Create the convergence test, the norm of the residual with a tolerance of
set Tol 1e-10;
set maxiter 100;#max. no of iterations
set printFlagDynamic 0;
test NormDispIncr $Tol $maxiter $printFlagDynamic;

# Create the solution algorithm, a Newton-Raphson algorithm
algorithm Linear

# Change the integration scheme to be displacement control
# node dof init Jd min max
integrator DisplacementControl $mon_node $mon_dof $dU 1 $dU $dU
analysis Static;
set ok 0;
set currentDisp 0.0;
puts "max. displacement= $maxU"
# perform the analysis
while {$ok == 0 && [expr {abs($currentDisp)}] < [expr {abs($maxU)}]} {#puts "while loop starting"
set ok [analyze 1]
# if the analysis fails try initial tangent iteration
set numIncr [expr ($maxU-$currentDisp)/$dU];
if {$ok != 0} {source test_algo_M_fi.tcl}
set currentDisp [nodeDisp $mon_node $mon_dof];
}
##############
waiting for your suggestions....

[vesna]

When you see something like that that indicates inappropriate definition of the recorder.

This one is not define properly:
recorder Node -file $output/disp$mon_node$C.out -time -node $mon_node -dof $mon_dof disp;

Try this one:
recorder Node -file [format "$output/disp%i%i.out" $mon_node $C] -time -node $mon_node -dof $mon_dof disp;

[tusharkantimandal]

vesna wrote:
> When you see something like that that indicates inappropriate definition of
> the recorder.
>
> This one is not define properly:
> recorder Node -file $output/disp$mon_node$C.out -time -node $mon_node -dof
> $mon_dof disp;
>
> Try this one:
> recorder Node -file [format "$output/disp%i%i.out" $mon_node $C]
> -time -node $mon_node -dof $mon_dof disp;
Hi Vesna,
Probably U have not get my query properly. Let me clear U:: There is no problem reg. node recorder. Problem is reg. the "Element recorder ..stress" for ShellMITC4 element. Plz. provide some example file. I am not getting any data in the recorder file for "element recorder strain/stress" otherthan the time steps.

[vesna]

your stress/strain recorders look ok to me. however, if there is any recorder upfront that was not defined properly the later ones won't work.

[tusharkantimandal]

vesna wrote:
> your stress/strain recorders look ok to me. however, if there is any
> recorder upfront that was not defined properly the later ones won't work.
Hi Vesna,
I have check my code once again. The node recorders, Element force recorder is working properly giving outputs of nodal displacement and Element forces at each vertices of that element specified but Element recorder for stress/strain/strain are giving blank output. I have tried with the -xml option as well, it giving the details like :
[ <ElementOutput eleType="ShellMITC4" eleTag="1" node1="1" node2="2" node3="3" node4="4">
<GaussPoint number="3" eta="0.57735" neta="0.57735">
<SectionOutput secType="MembranePlateFiberSection" secTag="1"/>
</GaussPoint>
</ElementOutput>
<Data>]
But in the "data" part only the time steps NO values of stress/strain/state for ShellMITC4.

Thanks again for your regular reply. and waiting for your valuable suggestions....

[tusharkantimandal]

vesna wrote:
> your stress/strain recorders look ok to me. however, if there is any
> recorder upfront that was not defined properly the later ones won't work.
Plz. run this code in your pc and check if it's working properly. Thank U in advance.

[vesna]

It seems that the Plate Fiber wrapper material does not support recorder arguments of Drucker Prager material.

You can only record forces and stresses of shell elements. Here is how you can record stresses:
recorder Element -file $output/stress1.out -time -ele 1 stresses

[gerber]

How can you match Drucker Prager with shell element via plate fiber section??? Does it work??
i thought that I couldn`t use plate fiber section in the last versions

[tusharkantimandal]

vesna wrote:
> It seems that the Plate Fiber wrapper material does not support recorder
> arguments of Drucker Prager material.
>
> You can only record forces and stresses of shell elements. Here is how you
> can record stresses:
> recorder Element -file $output/stress1.out -time -ele 1 stresses

I need strain outputs. Can it be calculated using any recorder command?

In stress recorder there are 8 outputs per gauss points: p11,p22,p1212, m11,m22,m12,q1,q2.
What those means? pij s are planer stress components like sigma11,sigma22, sigma12. q1 and q2 r the shear component perpendicular to the plane?
What are mij??

[tusharkantimandal]

gerber wrote:
> How can you match Drucker Prager with shell element via plate fiber
> section??? Does it work??
> i thought that I couldn`t use plate fiber section in the last versions
yea. it works. but it can not record the strain..only stresses..