thanks for your previous attention but my problem is still about yield point in spite of the reasonable ductility.
I would appreciate it if you could help me.
Actually I want to study different uniaxial materials behaviours and their strain stress diagrams. So I tried to made a simple model as a simple truss with a cyclic load to study the displacements and forces in order to have stress and strain diagram. At first I tried elastic material with no problem, but when I changed the material to "Elastic perfectly plastic" by "ElasticPP" command my simple file does not converge a bout given yield point.
It's about five weeks that I have been trying to solve this problem
but unfortunately I have not been successful.It is good to mention that I tried to consider the reasonable ductility as : .0001*20=0.002 m=0.2 cm------ 0.2/.1=2
There is my file in the following:
# units: N, m
wipe
# Create ModelBuilder (with two-dimensions and 2 DOF/node)
model BasicBuilder -ndm 2 -ndf 3
# Create nodes & add to Domain - command: node nodeId xCrd yCrd
node 1 0. 0.
node 2 1. 0.
# Set the boundary conditions - command: fix nodeID xResrnt? yRestrnt?
fix 1 0 1 1
fix 2 1 1 1
# Define materials for truss elements
uniaxialMaterial ElasticPP 1 200000. 0.001
# Create truss elements - command: element truss trussID node1 node2 A matID
element corotTruss 1 1 2 1 1
pattern Plain 2 Linear {
# Create the nodal load - command: load nodeID xForce yForce
load 1 1.0 0. 0.
}
# create a Recorder object for the nodal displacements at node 1
recorder Node -file disp1.out -time -node 1 -dof 1 disp
recorder Node -file reac2.out -time -node 2 -dof 1 reaction
# create a Recorder for element forces, one for global system and the other for local system
recorder Element -file eleGlobal.out -time -ele 1 localforces
recorder Element -file eleLocal.out -time -ele 1 basicForces
# Create the constraint handler, a Plain handler is used as homo constraints
constraints Plain
# Create the DOF numberer, the reverse Cuthill-McKee algorithm
numberer Plain
test EnergyIncr 1.0e-6 150
system BandGeneral
algorithm ModifiedNewton
set j 0.0001
for {set i 1} {$i<=40} {incr i 1} {
set j [expr -1.00*$j]
integrator DisplacementControl 1 1 $j
# create the analysis object
analysis Static
set ok [ analyze 20]
puts $i
}
puts "node 1 displacement: [nodeDisp 1]"
print node 1
print element