New question #216096 on Yade:
https://answers.launchpad.net/yade/+question/216096
Dear yade user,
Could anyone please help me to see my code whether is it correct or not to make
a biaxial undrained test in 2D (without periodic condition)?
I'm using "ThreeDTriaxialEngine", so I can use "strainRate1=strainRate2" to
avoid the volume change (Please correct me if my idea is wrong).
Is there anyone have an experience in doing the triaxial/biaxial undrained
test? What is the best way to model it?
Thank you for your help and your sharing.
Here is my code:
# -*- coding: utf-8 -*-
from yade import pack,log, plot
from utils import *
############################################
### DEFINING VARIABLES AND MATERIALS ###
############################################
num_spheres = 500 # number of spheres
compFricDegree = 30 # contact friction during the
confining phase
finalFricDegree = 30 # contact friction during the
deviatoric loading
rate = 0.01 # loading rate (strain rate)
damp = 0.1 # damping coefficient
stabilityThreshold = 0.001 # unbalancedForce
key = '_biax_undrained_' # simulation's name
young = 5e6 # contact stiffness
mn,mx=Vector3(0,0,0),Vector3(1,1,1) # corners of the initial packing
thick = 0.01 # thickness of the plates
## create materials for spheres and plates
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=radians(compFricDegree),density=2600,label='spheres'))
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=0,density=0,label='walls'))
## create walls around the packing
walls=utils.aabbWalls([mn,mx],thickness=thick,material='walls')
wallIds=O.bodies.append(walls)
## generate a random loose particles packing
sp=pack.SpherePack()
sp.makeCloud(Vector3(0,0,0.5),Vector3(1,1,0.5) ,-1,0.3333,num_spheres,False,
0.95)
O.bodies.append([utils.sphere(center,rad,material='spheres') for center,rad in
sp])
# Blocked certain degress of freedom to make 2D-Model in plane-XY
for k in O.bodies:
if isinstance(k.shape, Sphere): k.state.blockedDOFs='zXY'
# initial timestep
O.dt=.5*utils.PWaveTimeStep()
O.usesTimeStepper=True
############################
### DEFINING ENGINES ###
############################
triax=ThreeDTriaxialEngine(
## ThreeDTriaxialEngine will be used to control stress and strain. It
controls particles size and plates positions.
maxMultiplier=1.005, # spheres growing factor (fast growth)
finalMaxMultiplier=1.002, # spheres growing factor (slow growth)
thickness = thick,
stressControl_1 = False, #switch stress/strain control
stressControl_2 = False,
## The stress used for (isotropic) internal compaction
sigma_iso = 10000,
## Independant stress values for anisotropic loadings
sigma1=10000,
sigma2=10000,
internalCompaction=True, # If true the confining pressure is generated
by growing particles
Key=key, # passed to the engine so that the output file will have the
correct name
)
newton=NewtonIntegrator(damping=damp)
unb=unbalancedForce()
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],
[Ip2_FrictMat_FrictMat_FrictPhys()],
[Law2_ScGeom_FrictPhys_CundallStrack()]
),
GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8,
defaultDt=4*utils.PWaveTimeStep()),
triax,
TriaxialStateRecorder(iterPeriod=100,file='WallStresses'+key),
newton,
PyRunner(command='addPlotData()',iterPeriod=100)
]
#####################################################
### Exemple of how to record and plot data ###
#####################################################
def addPlotData():
plot.addData(unbalanced=unb,i=O.iter,
s_right=triax.stress(triax.wall_right_id)[0],s_top=triax.stress(triax.wall_top_id)[1],s_front=triax.stress(triax.wall_front_id)[2],
s_left=triax.stress(triax.wall_left_id)[0],s_bot=triax.stress(triax.wall_bottom_id)[1],s_back=triax.stress(triax.wall_back_id)[2],
exx=triax.strain[0],eyy=triax.strain[1],ezz=triax.strain[2],axial_strain=triax.strain[1],
dev_stress=triax.stress(triax.wall_top_id)[1]-triax.stress(triax.wall_right_id)[0],
conf_stress=triax.stress(triax.wall_right_id)[0],
vol_strain= triax.strain[0]+triax.strain[1]
)
# define what to plot
plot.plots={'i':('unbalanced'),'i
':('s_right','s_top','s_front','s_left','s_bot','s_back'),'
i':('exx','eyy','ezz'),
' axial_strain':('dev_stress', 'conf_stress'),' axial_strain
':('vol_strain'),
}
# show the plot
plot.plot()
#Display spheres with 2 colors for seeing rotations better
Gl1_Sphere.stripes=1
yade.qt.Controller(), yade.qt.View()
#######################################
### APPLYING CONFINING PRESSURE ###
#######################################
while 1:
O.run(1000, True)
#the global unbalanced force on dynamic bodies, thus excluding boundaries,
which are not at equilibrium
unb=unbalancedForce()
#average stress
#note: triax.stress(k) returns a stress vector, so we need to keep only the
normal component
meanS=(triax.stress(triax.wall_right_id)[0]+triax.stress(triax.wall_top_id)[1]+triax.stress(triax.wall_front_id)[2])/3
print 'unbalanced force:',unb,' mean stress: ',meanS
if unb<stabilityThreshold and
abs(meanS-triax.sigma_iso)/triax.sigma_iso<0.001:
break
O.save('confinedState'+key+'.yade.gz')
print "### Isotropic state saved ###"
##############################
### DEVIATORIC LOADING ###
##############################
#We move to deviatoric loading, let us turn internal compaction off to keep
particles sizes constant
triax.internalCompaction=False
# Change contact friction (remember that decreasing it would generate
instantaneous instabilities)
triax.setContactProperties(finalFricDegree)
#set independant stress control on each axis
triax.stressControl_1=triax.stressControl_2=True
# We turn all these flags true, else boundaries will be fixed
triax.wall_bottom_activated=True
triax.wall_top_activated=True
triax.wall_left_activated=True
triax.wall_right_activated=True
triax.wall_back_activated=True
triax.wall_front_activated=True
#If we want a triaxial loading at imposed strain rate, let's assign srain rate
instead of stress
##... we are tired of typing "True" and "False", we use implicit conversion
from integer to boolean
triax.stressControl_2=0
##... fix a maximum strain rate to go progressivly to the desired stress state
in direction 2
triax.strainRate1=0.01
triax.strainRate2=0.01
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