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[Sarath Chandra Reddy <question697174@xxxxxxxxxxxxxxxxxxxxx>]

New question #697174 on Yade:
https://answers.launchpad.net/yade/+question/697174

Dear friends,
I am a beginner in YADE. I am trying to simulate CD triaxial test. As a initial step, I am trying to create particle packing. I found that their are different ways for doing this i.e., using makeCloud, pack.randomDensePack with Compaction control and particle resizing.
I thick that pack.randomDensePack with Compaction control is similar to boundary contraction option in PFC 3D. But when I am trying to generate particle packing using this option, the unbalanced forces are not becoming less than the threshold value even when I tried different parameter values. Please advice on where I am going wrong with the parameter values or is there any mistakes in the code.

#Code for simple triaxial test
#Specify the variables
sigmaIso = 1.5e5 #Confining pressure
rMean = 0.00027 #Mean radius of the particles
rRelFuzz = 0.3 #The relative fuzz of the distribution
mn,mx = Vector3(0,0,0),Vector3(.00565,.00565,.00565)#The boundaries of the bounding box
initialFriction = 0.1 #Friction in radian
young=100e9 #Young's modulus of the particles
wallFriction=0 #Friction in the triaxial walls
num_spheres=6000#Predicted maximum number of spheres in simulation
rate = 1
targetPorosity=0.35 #Targeted porosity
finalFriction = .25 #Friction angle during deviatoric loading phase
sphere_density = 2650 #Density of the spheres
wall_density = 4000 #Density of the wall
wall_thickness = 0 #thickness of the walls

#Importing the relevant modules from yade
from yade import pack, qt, plot
O.materials.append(FrictMat(density=wall_density,young=young,frictionAngle=wallFriction, label='walls'))
O.materials.append(FrictMat(young=young,density=sphere_density,frictionAngle=initialFriction,label='sphere'))
#Appending the walls before we form the packing
walls=aabbWalls([mn,mx],thickness=wall_thickness, material='walls')
wallIds=O.bodies.append(walls)
#Using predicate to generate the sphere packing inside the walls
pred=pack.inAlignedBox((mn),(mx))
#Predicate and memorizeDb command saves it so that the packing can be used over and over again
sp=SpherePack()
sp=pack.randomDensePack(pred,radius=rMean,rRelFuzz=rRelFuzz,memoizeDb='/tmp/triaxpackcache.sqlite',returnSpherePack=True,material='spheres')
sp.toSimulation()
#Printing the mass of the spheres
print (utils.getSpheresMass(-1))
#Triaxial stress Controller
triax = TriaxialStressController(wall_bottom_id=wallIds[2],
                                 wall_top_id=wallIds[3],
                                 wall_left_id=wallIds[0],
                                 wall_right_id=wallIds[1],
                                 wall_back_id=wallIds[4],
                                 wall_front_id=wallIds[5],
                                 thickness=wall_thickness,
                                 #Stress controlled on three axes i.e., x*1+y*2+z*4
                                 stressMask=7,
                                 internalCompaction=False,
                                 label="triax"
                                 )
#Now we will start the engine
O.engines=[
           ForceResetter(),
           InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
           InteractionLoop(
           [Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],
           [Ip2_FrictMat_FrictMat_MindlinPhys(en=0.1,es=0.1)],    [Law2_ScGeom_MindlinPhys_Mindlin()]),
           GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.5),
           triax,
           NewtonIntegrator(damping=0.2)
           ]
#Applying Confining Pressure
triax.goal1=triax.goal2=triax.goal3=-sigmaIso

while 1:
        O.run(1000,True)
        unb=unbalancedForce(),
        print ('unbalanced force:',unb,'mean stress:',triax.meanStress,'pressure:',abs(-sigmaIso-triax.meanStress)/sigmaIso)
        if unbalancedForce() < .01 and (abs(-sigmaIso-triax.meanStress)/sigmaIso) < .1:
               break
        
print ("Particle Distribution is Stable")

import sys

#while triax.porosity>targetPorosity:
 #      initialFriction=0.95*initialFriction
 #      setContactFriction(initialFriction)
  #     print ("Friction:",initialFriction,"Porosity:",triax.porosity)
  #     sys.stdout.flush()
   #    O.run(500,1)
print ("Time for the deviator loads")

setContactFriction(finalFriction)
O.run(1000,True)
triax.internalCompaction=False
setContactFriction(finalFriction)
triax.stressmask=5
triax.goal2=-rate
triax.goal1=-sigmaIso
triax.goal2=-sigmaIso
O.engines = O.engines+[PyRunner(command='addPlotData()',iterPeriod=50000)]

def addPlotData():
# Lets start by defining a function that adds the data to a text file
    e11=-triax.strain[0]
    e22=-triax.strain[1]
    e33=-triax.strain[2]
    s11=-triax.stress(triax.wall_right_id)[0]
    s22=-triax.stress(triax.wall_top_id)[1]
    s33=-triax.stress(triax.wall_front_id)[2]
    plot.addData(Strain=e22,StressX=s11,StressY=s22,StressZ=s33,DeviatorStress=((s22-((s11+s33)/2))*1e-6))
    plot.saveDataTxt('data.txt',vars=('Strain','DeviatorStress','StressX','StressY','StressZ'))
    
    
plot.plots={'Strain':('DeviatorStress')}
plot.plot()

    #Finally we run the simulation automatically
O.run()              

Thanking you in advance,
Sarath     
          

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