Cohesive triaxial

for example below script will work for
         sigmaIsoCompaction=-150e3,
 sigmaLateralConfinement=-150e3,
if I change the to 50e3 results are not make sense ( much lower that experimental results)

# encoding: utf-8
# 2012 ©Bruno Chareyre <email address hidden>
# This variant of triax-basic.py shows the usage of cohesive contact laws and moments at contacts

from yade import pack

sp=pack.SpherePack()
## corners of the initial packing
mn,mx=Vector3(0,0,0),Vector3(10,10,10)

## box between mn and mx, avg radius ± ½(20%), 2k spheres
sp.makeCloud(minCorner=mn,maxCorner=mx,rRelFuzz=.2,num=1000)

## create material #0, which will be used as default
O.materials.append(CohFrictMat(young=229e6,poisson=0.4,density=2600,frictionAngle=radians(36.5),normalCohesion=1e6,shearCohesion=1e6,momentRotationLaw=True,etaRoll=0.14,label='spheres'))
O.materials.append(FrictMat(young=229e6,poisson=.4,frictionAngle=0,density=0,label='frictionlessWalls'))

## copy spheres from the packing into the scene
O.bodies.append([sphere(center,rad,material='spheres') for center,rad in sp])
## create walls around the packing
walls=aabbWalls(material='frictionlessWalls')
wallIds=O.bodies.append(walls)

triax=TriaxialCompressionEngine(
 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],
 internalCompaction=False,
 sigmaIsoCompaction=-50e3,
 sigmaLateralConfinement=-50e3,
 max_vel=10,
 strainRate=0.03,
 label="triax"
)

O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
 InteractionLoop(
  #box-sphere interactions will be the simple normal-shear law, we use ScGeom for them
  [Ig2_Sphere_Sphere_ScGeom6D(),Ig2_Box_Sphere_ScGeom()],
  #Boxes will be frictional (FrictMat), so the sphere-box physics is FrictMat vs. CohFrictMat, the Ip type will be found via the inheritance tree (CohFrictMat is a FrictMat) and will result in FrictPhys interaction physics
  #and will result in a FrictPhys
  [Ip2_FrictMat_FrictMat_FrictPhys(),Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(label="cohesiveIp")],
  #Finally, two different contact laws for sphere-box and sphere-sphere
  [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=100,file='50e3,young=229e6,poisson=0.4,density=2600,frictionAngle=radians(36.5),normalCohesion=1e6,shearCohesion=1e6,etaRoll=0.14,'),
 NewtonIntegrator(damping=.4)
]

from yade import plot
O.engines=O.engines[0:5]+[PyRunner(iterPeriod=20,command='history()',label='recorder')]+O.engines[5:7]
def history():
   plot.addData(e11=-O.engines[4].strain[0], e22=-O.engines[4].strain[1], e33=-O.engines[4].strain[2],
      s11=-O.engines[4].stress(0)[0],
      s22=-O.engines[4].stress(2)[1],
      s33=-O.engines[4].stress(4)[2],
      i=O.iter)

#plot.plots={'i':(('e11',"bo"),('e22',"ro"),('e33',"go"),None,('s11',"bx"),('s22',"rx"),('s33',"gx"))}
plot.plots={'e22':'s22'}
plot.plot()

print "computing, be patient..."
#First run without moment and without cohesion
O.run(20000,True)

#This will reload the autosaved compacted sample
O.reload()

#second run with rolling friction
O.engines[2].lawDispatcher.functors[1].always_use_moment_law = True
O.run(20000,True)
O.reload()

#third run with rolling friction + cohesion
O.engines[2].lawDispatcher.functors[1].always_use_moment_law = True
#We assign cohesion to all contacts at the next iteration
O.engines[2].physDispatcher.functors[1].setCohesionNow = True
O.run(30000,True)

Thanks for help
seti

Dear Seti,
"the results are not convenience" is not the _description_ of a problem.
Please check https://yade-dem.org/wiki/Howtoask
Bruno

Hi all,

I am a little confused on cohesion setting of particles. As I read the above code, does it mean:

1. when we use: [Laws_ScGeom6D_CohFrictPhys_CohesionMoment()], the cohesion between particles is not activated;
2. the cohesion is only activated when we use "O.engines[2].phyDispatcher.functors[0].setCohesionNow = True"

Am I correct? Please correct me if I make a mistake. Thanks so much.

Best,
Zheng