[Yade-users] [Question #632092]: CohFrictMat fragile mode does not break interaction
New question #632092 on Yade:
https://answers.launchpad.net/yade/+question/632092
Hi everybody !
I am trying to test what exactly do the fragile and plastic mode of
CohFrictMat, and for this I have implemented a very simple simulation,
appending a fixed sphere, and a second one who is moving the opposite way from
initial contact, in order to break the cohesion bond by exceeding the tensile
strength limit.
I am plotting Fn versus un displacement, and when I run the simulation using
Fragile = False in the simulation I get first elastic increase of fn, and then
flat plastic behavior, then the two particles are set apart, and interaction
disappears. Which is fine.
However, when I use fragile = True, the same elastic behavior initially occurs,
up until the fragile limit, then, at that precise timestep, no interaction is
detected by Yade, and then this interaction is reset, with a very high value,
and that does not drop to zero until the particles are really apart ( they are
still overlapping when the strenght limit is reached, and that is because they
are initially overlapping).
So I don't really know what is going on here. Could it be that it is the
setting of the equilibrium distance again ? since unp relates to plastic
displacement ?
any help would be appreciated !
Here is the script, running already until the strenght limit is reached,
pressing run you can see what happens next !
# coding=utf-8
# TEST 8 : Appliance of horizontal disp one ball (rebound)-- > no grav/no coh
# EXPECTED : we want to see breakage of cohesion bond
from __future__ import division
import numpy as np
from yade import plot,pack,timing
from pprint import pprint
# DATA COMPONENTS
nb_iter = 1
# INPUTS
# Geometry
RSph = 0.1
CoeffSph = 0.9
Pos1 = (RSph*CoeffSph,RSph,0.)
Pos2 = (-RSph*CoeffSph,RSph,0.)
# Material
EyCohFrictMat = 1e7
poissonCohFrictMat = 0.25
densityCohFrictMat = 2600.
FrictAngSphere = 30.*pi/180.
NCohesionCohFrictMat = 3
SCohesionCohFrictMat = 3
# Calculation
damp=0.5
gz=0.
SphereVel= (-1.5,0.,0.)
#EXPORTATION
#création des différentes listes de forces
lisForce = []
lisForN = []
lisForSh = []
lisTime = []
"
# SIMULATION BEGINNING - SIMULATION BEGINNING - SIMULATION BEGINNING
## CREATE MATERIAL - CREATE MATERIAL - CREATE MATERIAL
O.materials.append(
CohFrictMat(
young = EyCohFrictMat,
poisson= poissonCohFrictMat,
density= densityCohFrictMat ,
frictionAngle = FrictAngSphere,
normalCohesion = NCohesionCohFrictMat ,
shearCohesion = SCohesionCohFrictMat ,
fragile = True,
momentRotationLaw=True,
etaRoll=0.1,
etaTwist=-1,
alphaKr=0.,
alphaKtw=0.,
isCohesive = True,
label='MatSpheres'))
## CREATE SPHERES - CREATE SPHERES - CREATE SPHERES -
# they could use the default material (utils.defaultMat)
O.bodies.append([
# fixed: particle's position in space will not change
sphere(center=Pos1,radius= RSph,fixed=True, material ='MatSpheres'),
# this particles is free, subject to dynamics
sphere(Pos2,RSph, material ='MatSpheres')
])
setBodyVelocity(1,SphereVel, 'xyz')
## FUNCTIONAL COMPONENTS - FUNCTIONAL COMPONENTS - FUNCTIONAL COMPONENTS -
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb()]),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom6D(interactionDetectionFactor=1.5,label='ss2sc')],
# collision geometry
[Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(setCohesionNow = True)], #
collision "physics"
[Law2_ScGeom6D_CohFrictPhys_CohesionMoment(useIncrementalForm = True)]
# contact law -- apply forces
),
#Apply gravity force to particles. damping: numerical dissipation of energy.
NewtonIntegrator(gravity=(0.,0.,gz)),
PyRunner(command='addPlotData()',iterPeriod=1, dead= True, label =
'dataPlot')
]
def setEquilibrium():
O.dt = 0.
O.step()
for i in O.interactions :
i.phys.unp = i.geom.penetrationDepth
O.step()
dataPlot.dead = False
ss2sc.interactionDetectionFactor=1. # now reset the interaction radius
and go ahead
O.dt=5e-4*PWaveTimeStep()
def addPlotData():
yade.plot.addData({'t':O.time,'i':O.iter,'Fn':O.interactions[0,1].phys.normalForce[0]
,'Fs':O.interactions[0,1].phys.shearForce[0], 'un':SphereVel[0]*O.time
})
#pprint (plot.data)
setEquilibrium()
plot.plots={'un':('Fn')}
plot.plot()
O.run(250,True)
yade.qt.Controller(), yade.qt.View()
cheers,
Manon
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