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[Leonard <question686278@xxxxxxxxxxxxxxxxxxxxx>]

New question #686278 on Yade:
https://answers.launchpad.net/yade/+question/686278

Hi,
In [1], it shows a method to reach isotropic state  by using particle growing (internalCompaction=True). However, if we use this method, there will be a scale up from initial (i.e. input) particle size  distribution, like Figure 1 in [2]. What I want to achieve is to reach isotropic state without particle growing, something like the PSD curve in Figure 9 in [3]. So I set internalCompaction=False in order to keep constant particle size. The problem is when I set internalCompaction=False, the size of the sample changed.
For example, the size of initial packing is 0.7*0.7*1.4 (i.e. mn,mx=Vector3(0,0,0),Vector3(0.7,0.7,1.4)), when I set internalCompaction=True, after compacted state completed, the size of the packing stays around 0.7*0.7*1.4. However, when I set internalCompaction=False, after compacted state completed, the size of the packing is changed to 0.26*0.26*0.9, and in this case, I can not obtain a reasonable sample in terms of size. The following MWE may show this question by changing internalCompaction= True to False.
###########
from yade import pack, plot
nRead=readParamsFromTable(
 num_spheres=1000,
 compFricDegree = 30,
 key='_triax_base_',
 unknownOk=True
)
from yade.params import table

num_spheres=table.num_spheres
key=table.key
targetPorosity = 0.43
compFricDegree = table.compFricDegree
finalFricDegree = 30
rate=-0.02
damp=0.2
stabilityThreshold=0.01
young=5e6
mn,mx=Vector3(0,0,0),Vector3(0.7,0.7,1.4)

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'))
walls=aabbWalls([mn,mx],thickness=0,material='walls')
wallIds=O.bodies.append(walls)

sp=pack.SpherePack()
sp.makeCloud(mn,mx,-1,0.3333,num_spheres,False, 0.95,seed=1)
O.bodies.append([sphere(center,rad,material='spheres') for center,rad in sp])

Gl1_Sphere.quality=3

### DEFINING ENGINES ###
triax=TriaxialStressController(
 maxMultiplier=1.+2e4/young,
 finalMaxMultiplier=1.+2e3/young,
 thickness = 0,
 stressMask = 7,
 internalCompaction=True,## please change True to False here to look at what I say
)

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_FrictPhys()],
  [Law2_ScGeom_FrictPhys_CundallStrack()]
 ),
 GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
 triax,
 newton
]

Gl1_Sphere.stripes=0
if nRead==0: yade.qt.Controller(), yade.qt.View()

### APPLYING CONFINING PRESSURE ###
triax.goal1=triax.goal2=triax.goal3=-10000
while 1:
 O.run(1000, True)
 unb=unbalancedForce()
 print 'unbalanced force:',unb,' mean stress: ',triax.meanStress
 if unb<stabilityThreshold and abs(-10000-triax.meanStress)/10000<0.001:
  break

print "### Isotropic state saved ###"
### REACHING A SPECIFIED POROSITY PRECISELY ###
import sys
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)
print "### Compacted state saved ###"
########################

Could you please give some instructions?
Thanks,
Leonard

[1]https://github.com/yade/trunk/blob/master/examples/triax-tutorial/script-session2.py
[2]https://link.springer.com/article/10.1007/s11440-017-0593-6
[3]https://link.springer.com/article/10.1007%2Fs10035-016-0687-0

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