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[Seti <question273812@xxxxxxxxxxxxxxxxxxxxx>]

New question #273812 on Yade:
https://answers.launchpad.net/yade/+question/273812

Hi guys!
I am trying to do parametric study for triaxial test. I have played around the friction angle and alphaKr. However  changing of these two parameters have no effect on my results. I am not sure where is my mistake . Would you please advice me.

Thanks heaps,

Here is my code:
from yade import pack
nRead=utils.readParamsFromTable(
        num_spheres=1000,# number of spheres len(O.bodies) to verify: 10006 = 10000 particles + 6 walls is correct
        compFricDegree = 30, # contact friction during the confining phase (1)
        unknownOk=True,
        isoForce=200000, # stress for the isotropic compression phase (1)
        conStress=200000 # confinement stress, for the deviatoric loading session (2)
)
from yade.params import table
 
num_spheres=table.num_spheres                   # number of spheres called from table
targetPorosity = 0.8                         #the porosity we want for the packing (3 specimens: (Ei,n) = (1,0.382), (2,0.387), (3,0.409) )
compFricDegree = table.compFricDegree   # initial contact friction during the confining phase (will be decreased during the REFD compaction process)
finalFricDegree = 30                                    # contact friction during the deviatoric loading
rate=0.001                                                                # loading rate (strain rate)
damp=0.3                                                               # damping coefficient
stabilityThreshold=0.001                                # initial value: 0.001
key='_kozooooooooooooooocki,,200kpa,200kpa,30,30,30e9_0.12,0.12,0.12,alphaKr=0.15,BREAK0.7,.001'                         # simulation's name here
young=30e9                                                     # contact stiffness k_n/Ds
mn,mx=Vector3(-0.12,-0.12,-0.12),Vector3(0.12,0.12,0.12) # corners of the initial packing
thick = 0.01                                                    # thickness of the plates
 
 
## create materials for spheres and plates
O.materials.append(CohFrictMat(alphaKr=0.15,young=young,poisson=0.3,frictionAngle=radians(compFricDegree),momentRotationLaw=True,etaRoll=1,density=2600,label='spheres'))
O.materials.append(FrictMat(young=young,poisson=0.3,frictionAngle=0,density=0,label='walls'))
 
## create walls around the packing
walls=utils.aabbWalls([mn,mx],thickness=thick,oversizeFactor=1.5,material='walls')
wallIds=O.bodies.append(walls)
 
## use a SpherePack object to generate a random loose particles packing
sp=pack.SpherePack()
psdSizes=[0.002,0.003,0.004,0.005,0.006,0.007,0.008] # (sizes or radii of the grains vary from 2mm to 9.5mm)
#psdCumm=[1,9,25,50,69,90,95,100] # the correspondent amount (percentage) of each diameter, uncomment for yade-stable
psdCumm=[0.14,0.28,0.34,0.50,0.65,0.85,1.00] # for the code not using percentage, e.g. yade-daily
sp.makeCloud(mn,mx,0.00575,0.6,num_spheres,False,0.95,seed=1)
sp.toSimulation(material='spheres')
triax=TriaxialStressController(
        maxMultiplier=1.001, # spheres growing factor (fast growth), validated only when internalCompaction = True
        finalMaxMultiplier=1.00001, # spheres growing factor (slow growth), validated only when internalCompaction = True
        thickness = thick,
stressMask = 7,
        #the value of confining stress for the intitial (growth) phase
        goal1=table.isoForce,
        goal2=table.isoForce,
        goal3=table.isoForce,
        max_vel=0.5, # validated only when internalCompaction = False m/s
        internalCompaction=True,)
newton=NewtonIntegrator(damping=damp)
 
O.engines=[
        ForceResetter(),
        InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
        InteractionLoop(
                [Ig2_Sphere_Sphere_ScGeom6D(),Ig2_Box_Sphere_ScGeom()],
                [Ip2_FrictMat_FrictMat_FrictPhys  (),Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(label="cohesiveIp")],
                [Law2_ScGeom_FrictPhys_CundallStrack(),Law2_ScGeom6D_CohFrictPhys_CohesionMoment(
			useIncrementalForm=True, #useIncrementalForm is turned on as we want plasticity on the contact moments
			always_use_moment_law=False,  #if we want "rolling" friction even if the contact is not cohesive (or cohesion is broken), we will have to turn this true somewhere
			label='cohesiveLaw')]
        ),
GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.5),
        triax,
        TriaxialStateRecorder(iterPeriod=50,file='WallStresses'+key),
        newton
]
###   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
  print 'void ratio=',triax.porosity/(1-triax.porosity), 'porosity=', triax.porosity
  print 'mean stress of engine', triax.meanStress
  print '0.12,0.12,0.12,alphaKr=0.15,BREAK0.7,.001'
  if triax.porosity<0.7:
    break
##################################################
###   REACHING A SPECIFIED POROSITY PRECISELY   ###
import sys #this is only for the flush() below
while triax.porosity>targetPorosity:
        # # we decrease friction value and apply it to all the bodies and contacts
        compFricDegree = 0.95*compFricDegree
        setContactFriction(radians(compFricDegree))
        print "\r Friction: ",compFricDegree," porosity:",triax.porosity,
        sys.stdout.flush()
        O.run(500,1)
##############################
###   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))
setContactFriction(radians(30))
 
#set stress control on x and z, we will impose strain rate on y (5)
triax.stressMask = 5
#now goal2 is the target strain rate
triax.goal2=-rate
#we assign constant stress to the other directions
triax.goal1=table.conStress
triax.goal3=table.conStress
 
##we can change damping here. What is the effect in your opinion?
#newton.damping=0.1
 
##Save temporary state in live memory. This state will be reloaded from the interface with the "reload" button.
O.saveTmp()
 
 
while triax.strain[1] < 0.25:
  O.run(50); O.wait()

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