randomDensePack explodes because of penetrationDepth

Hi Tina,

see [1], Jerome's answer #4. The problem is that after InteractionLoop, the particles are moved by NewtonIntegrator, so i.geom.penetrationDepth is the old value and setting it as i.phys.unp is nto enough.

One option is setting O.dt=0 for the first step (don't know how it works with GlobalStiffnessTimeStepper, probably should be deactivated for the first step?)

O.dt = 0
for i in O.interactions:
  i.phys.unp = i.geom.penetrationDepth
O.dt = ...

then I had no explosion

cheers
Jan

sorry, the reference for previous post :-)

[1] https://answers.launchpad.net/yade/+question/266828

Hi Jan,

Thanks for your help, but I still got a explosion. Here is my script:

from yade import pack
from yade import qt,utils

stone=CohFrictMat(young=5.0e10,poisson=0.25,density=2640,frictionAngle=radians(18),isCohesive=True,normalCohesion=4.5e6,shearCohesion=4.5e7,momentRotationLaw=True)
O.materials.append(stone)
steel=CohFrictMat(young=3.06e11,poisson=0.29,density=7861,frictionAngle=0.545,normalCohesion=0,shearCohesion=0)
O.materials.append(steel)

pred=pack.inSphere((0,0,0.5),0.25)
#sphs=pack.regularHexa(pred,radius=0.01,gap=0,material=stone)
sphs=pack.randomDensePack(pred,radius=0.025,rRelFuzz=0,material=stone)
O.bodies.append(sphs)

for i in sphs:
    velocity=i.state.vel=(0,0,-25)

O.bodies.append(geom.facetBox((0,0,0.2),(0.3,0.3,0.003),material=steel))

O.engines=[
    ForceResetter(),
    InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=1.5),Bo1_Facet_Aabb()]),
    InteractionLoop(
        [Ig2_Sphere_Sphere_ScGeom6D(interactionDetectionFactor=1.5),Ig2_Facet_Sphere_ScGeom6D()],
        [Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(setCohesionNow=True)],
        [Law2_ScGeom6D_CohFrictPhys_CohesionMoment()]
        ),
    #VTKRecorder(fileName='post/0deg-',recorders=['all'],iterPeriod=50),
    #GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=5,timestepSafetyCoefficient=0.8,defaultDt=PWaveTimeStep()),
    NewtonIntegrator(damping=0.3,gravity=(0,0,-9.81)),

]

O.dt = 0
for i in O.interactions:
    i.phys.unp = i.geom.penetrationDepth
O.dt=0.3e-7

qt.Controller()
qt.View()

Recently, I have tried many methods:
As it was posted in https://answers.launchpad.net/yade/+question/266828, I added this code segment into my script, but also failed:

O.bodies.dynamic=False
O.step()
for j in O.interactions:
    j.phys.unp = j.geom.penetrationDepth
O.bodies.dynamic=True
O.dt=0.3e-7

I guess the explosion was a consequence of the repulsive force was greater than the bonded strength between contacting particles.

Thanks for your patience!

Tina @ Yade

Thanks Jan,

Sorry for my carelessness!

Thanks for your patience!

Tina

Thanks Jan Stránský, that solved my question.