New question #231633 on Yade:
https://answers.launchpad.net/yade/+question/231633
Dear all,
I'm having a problem regarding setting stress mask in triaxial example. I've
read other posts related to my problem but it still exists. I need STRAIN
controlled loading in the 2nd phase of trixial test. I want to apply a similar
strian rate in all 3 directions in order to achieve a mean stress of 4 MPa.
I've set the stress mask value to 0 and 7 respectively but still the walls
don't move. How should I modify the code to get all of the walls moving with
the same rate. Thanks in advance for your kind answers. My script is as follows:
from yade import pack,plot
import matplotlib; matplotlib.rc('axes',grid=True)
import pylab
############################################
### DEFINING VARIABLES AND MATERIALS ###
############################################
psdSizes=[.107*0.86,.132*0.86,.216*0.86,.399*0.86,.885*0.86,.97*0.86,1.113*0.86,1.359*0.86,1.633*0.86,1.993*0.86,2.433*0.86]
psdCumm=[0.*100,.0643*100,.1969*100,.1969*100,.2*100,.2988*100,.4004*100,.5515*100,.6965*100,.8476*100,1.*100]
pylab.plot(psdSizes,psdCumm)
pylab.xscale('log')
pylab.gcf().savefig('psd.pdf')
compFricDegree = 0, # contact friction during the confining phase
finalFricDegree = 26.5 # contact friction during the deviatoric loading
rate=0.1 # loading rate (strain rate)
damp=0.5 # damping coefficient
stabilityThreshold=0.01 # we test unbalancedForce against this value in
different loops (see below)
key='_Cu=3_' # put you simulation's name here
young=52e9 # contact stiffness
## create materials for spheres and plates
O.materials.append(FrictMat(young=52e9,poisson=.35,frictionAngle=radians(0),density=2000,label='spheres'))
O.materials.append(FrictMat(young=52e9,poisson=.2,frictionAngle=0,density=0,label='walls'))
## create walls around the packing
walls=utils.aabbWalls([(0,0,0),(13.244,13.244,13.244)],oversizeFactor=1)
wallIds=O.bodies.append(walls)
## use a SpherePack object to generate a random loose particles packing
sp=pack.SpherePack();
sp.particleSD2(radii=psdSizes,passing=psdCumm,numSph=15000,cloudPorosity=0.585,seed=1)
O.bodies.append([utils.sphere(center,rad,material='spheres') for center,rad in
sp])
############################
### DEFINING ENGINES ###
############################
triax=TriaxialStressController(
maxMultiplier=1.0000025, # spheres growing factor (fast growth)
finalMaxMultiplier=1.00000025, # spheres growing factor (slow growth)
thickness = 0,
## switch stress/strain control using a bitmask. What is a bitmask,
huh?!
## Say x=1 if stess is controlled on x, else x=0. Same for for y and z,
which are 1 or 0.
## Then an integer uniquely defining the combination of all these tests
is: mask = x*1 + y*2 + z*4
## to put it differently, the mask is the integer whose binary
representation is xyz, i.e.
## "100" (1) means "x", "110" (3) means "x and y", "111" (7) means "x
and y and z", etc.
stressMask = 7,
internalCompaction=True, # If true the confining pressure is generated
by growing particles
)
newton=NewtonIntegrator(damping=damp)
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],
[Ip2_FrictMat_FrictMat_MindlinPhys()],
[Law2_ScGeom_MindlinPhys_MindlinDeresiewitz()]
),
GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
triax,
TriaxialStateRecorder(iterPeriod=100,file='WallStresses'+key),
newton
]
#######################################
### APPLYING CONFINING PRESSURE ###
#######################################
#the value of (isotropic) confining stress defines the target stress to be
applied in all three directions
triax.goal1=triax.goal2=triax.goal3=100000
while 1:
O.run(2500, True)
#the global unbalanced force on dynamic bodies, thus excluding boundaries,
which are not at equilibrium
unb=unbalancedForce()
fi = open('%s.xls'%"radius of each body",'w')
fi.write('%s\n'%' ')
fi.write('%s\n'%' ')
fi.write('%s\n'%' ')
fi.write('%s\n'%' ')
fi.write('%s\n'%' ')
fi.write('%s\n'%' ')
fi.write('%s\n'%' ')
fi.write('%s\n'%' ')
fi.write('%s\n'%' ')
for m in O.bodies:
if isinstance(m.shape,Sphere):
radii=m.shape.radius
fi.write('%s\n'%str(radii))
print 'unb-force: ',unb,' mean stress: ',triax.meanStress,' Iteration:
',O.iter
if unb<stabilityThreshold and abs(100000-triax.meanStress)/100000<0.01:
break
O.save('confinedState'+key+'.yade.gz')
print "### Isotropic state saved ###",' Calculation Time=
',O.realtime
#############################
## 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)
setContactFriction(radians(finalFricDegree))
#set stress control on x and z, we will impose strain rate on y
triax.stressMask = 7
#now goal2 is the target strain rate
triax.goal2=-rate
# we define the lateral stresses during the test, here the same 10kPa as for
the initial confinement.
triax.goal1=-rate
triax.goal3=-rate
thickness=1
#Save temporary state in live memory. This state will be reloaded from the
interface with the "reload" button.
O.saveTmp()
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