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[Sina Jafari <question246254@xxxxxxxxxxxxxxxxxxxxx>]

New question #246254 on Yade:
https://answers.launchpad.net/yade/+question/246254

hi all,
I'm working on triax example. I changed contact law to mindlin and tried to run the simulation again but in radius expansion(internal compaction) phase, UNREAL results appear which are not acceptable and don't make sense. When I change the law to cundallStrack everything gets back to normal. what is happening here? would be thankful if you help me with that.
here is my script:

from yade import pack,plot
import matplotlib; matplotlib.rc('axes',grid=True)
import pylab
############################################
###   DEFINING VARIABLES AND MATERIALS   ###
############################################
key='_Kenney_'
num_spheres=48710
psdSizes,psdCumm=[0.262,0.53,0.97,1.76,2.49,3.4,4.87,6.4],[0.1,3.4,9.1,19.1,29.4,48.7,81.5,100]
#targetPorosity = 0.387 #the porosity we want for the packing
compFricDegree = 26.5 # initial contact friction during the confining phase (will be decreased during the REFD compaction process)
finalFricDegree = 26.5 # contact friction during the deviatoric loading
rate=0.001 # loading rate (strain rate)
damp=0.2 # damping coefficient!!!!!!!!!!
stabilityThreshold=0.01 # we test unbalancedForce against this value in different loops (see below)
young=540e6 # contact stiffness
#mn,mx=Vector3(0,0,0),Vector3(53.52,53.52,53.52) # corners of the initial packing


## create materials for spheres and plates
O.materials.append(FrictMat(young=young,poisson=0.35,frictionAngle=radians(compFricDegree),density=2000,label='spheres'))
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=0,density=0,label='walls'))

# create walls around the packing
#walls=aabbWalls([mn,mx],material='walls',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=7500,cloudPorosity=0.55,seed=1)
O.bodies.append([utils.sphere(center,rad,material='spheres') for center,rad in sp])
walls=aabbWalls(material='walls',oversizeFactor=1)
wallIds=O.bodies.append(walls)
#or alternatively (higher level function doing exactly the same):
#sp.toSimulation(material='spheres')

############################
###   DEFINING ENGINES   ###
############################

triax=TriaxialStressController(
	## ThreeDTriaxialEngine will be used to control stress and strain. It controls particles size and plates positions.
	## this control of boundary conditions was used for instance in http://dx.doi.org/10.1016/j.ijengsci.2008.07.002
	maxMultiplier=1.+1e3/young, # spheres growing factor (fast growth)!!!!!!
	finalMaxMultiplier=1.+1e2/young, # 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_Mindlin()]
	),
	## We will use the global stiffness of each body to determine an optimal timestep (see https://yade-dem.org/w/images/1/1b/Chareyre&Villard2005_licensed.pdf)
	GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
	triax,
	TriaxialStateRecorder(iterPeriod=100,file='WallStresses.dat'),
	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(1000, True)
  #the global unbalanced force on dynamic bodies, thus excluding boundaries, which are not at equilibrium
  unb=unbalancedForce()
  print 'unbalanced force:',unb,' mean stress: ',triax.meanStress
  if unb<stabilityThreshold and abs(100000-triax.meanStress)/100000<0.01:
    break

O.save('confinedState'+'.yade.gz')
print "###      Isotropic state saved      ###"
print 'ACN=',utils.avgNumInteractions(),'Porosity=',utils.voxelPorosityTriaxial(triax),'Calculation Time(Sec)=',O.realtime

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