New question #683380 on Yade:
https://answers.launchpad.net/yade/+question/683380
Hi,
I am using CohFrictMat to investigate the bond effect, starting from very
simple assembly, for example: two sands bonded by two cements, fix one sand and
give a constant velocity on another sand. Here is the script running on Yade
2018.02b, ubuntu 18.04.
from yade import pack, plot
cement =
CohFrictMat(young=30e9,poisson=0.3,frictionAngle=radians(30),density=2650.0,normalCohesion=1e10,
shearCohesion=1e9,label='cement')
O.materials.append(cement)
s1=utils.sphere((0,0,0),radius=1,color=[1,1,1],fixed=True,material='cement')
s2=utils.sphere((0,0,2),radius=1,color=[1,1,1],material='cement')
s3=utils.sphere((0,sqrt(0.44),1),radius=0.2,color=[0,0.8,0],material='cement')
s4=utils.sphere((0,-sqrt(0.44),1),radius=0.2,color=[0,0.8,0],material='cement')
O.bodies.append(s1)
O.bodies.append(s2)
O.bodies.append(s3)
O.bodies.append(s4)
s2.state.blockedDOFs='z'
s2.state.vel = Vector3(0,0,-1e1)
Gl1_Sphere.quality=3
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb()]),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom6D()],
[Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(setCohesionNow =
True,setCohesionOnNewContacts = True)],
[Law2_ScGeom6D_CohFrictPhys_CohesionMoment()]
),
NewtonIntegrator(damping=0.4),
PyRunner(iterPeriod=100,command='addPlotData()',label='plotData'),
]
## run for one step to generate interactions
O.step()
def addPlotData():
plot.addData(i=O.iter,
displacement=1.8-O.bodies[1].state.pos[2],
force_sand=O.forces.f(1)[2],
normalForce_cement=O.interactions[1,2].phys.normalForce.norm(),
shearForce_cement=O.interactions[1,2].phys.shearForce.norm(),
normalAdhesion=O.interactions[1,2].phys.normalAdhesion,
shearAdhesion=O.interactions[1,2].phys.shearAdhesion)
plot.plots={'displacement':('force_sand',),
'i':('normalAdhesion'),
'i ':('shearAdhesion'),
'normalForce_cement':('shearForce_cement'),}
plot.plot()
My questions are:
1. Which parameters in Yade define the bond strength (normal strength/ shear
strength)?
To my best understanding, one contact bond fails when the normal/ shear force
exceeds the corresponding strength, I reviewed some answered questions and
found that it may be related to cohesion which is defined in CohFrictMat, and
may be related to interactions.phys.normalAdhesion/ shearAdhesion, so I am
confused about which parameters define the bond strength.
2. How can we control the value of O.interactions.phys.normalAdhesion/
shearAdhesion?
In this simulation, when I change the value of normalCohesion and/or
shearCohesion in CohFrictMat, the force of sand can reach different values at
the moment when the two cement spheres are ejected away, it is reasonable since
the two cements with higher cohesion can lead to higher stiffness of the
assembly. However, when I change the normalCohesion and/or shearCohesion in
CohFrictMat, there is no change for the normalAdhesion / shearAdhesion, Does it
mean that there is no relationship between normalCohesion in CohFrictMat and
normalAdhesion in O.interactions.phys? If so, how can we control the
interactions.phys.normalAdhesion/ shearAdhesion?
3.I want to assign cohesion to all existing contacts not only in current
time-step, but alse in steps as long as the cement particles contact to sand
particles, is it right to set both "setCohesionNow" and
"setCohesionOnNewContacts" to True?
4. In the graph"normalForce_cement--shearForce_cement", why there are two
lines? I thought at the moment when the cement particles are ejected away, the
normal force and shear force would quickly drop to zero like the other three
graphs.
Many thanks!
Leonard (Aoxi)
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