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[Jan Stránský <question255528@xxxxxxxxxxxxxxxxxxxxx>]

Question #255528 on Yade changed:
https://answers.launchpad.net/yade/+question/255528

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hi Yuan,
accodring to your description, it seems like time step instability problem.
Could you try your script with decreased time step? PWaveTimeStep takes
into account only normal stiffnes and does not include rolling nor twist
stiffness, which might be the source of problems.
cheers
Jan


2014-10-20 7:16 GMT+02:00 Yuan <question255528@xxxxxxxxxxxxxxxxxxxxx>:

> Question #255528 on Yade changed:
> https://answers.launchpad.net/yade/+question/255528
>
>     Status: Answered => Open
>
> Yuan is still having a problem:
> Hi Jérôme and all YADE users,
>
> Thank you so much for you kindly help last time.
>
> After learning some basics of YADE, I started building my simulation by
> modifying a file(uniax.py) I found on GitHub.  However when I ran the
> simulation it became unstable. All the particles were flying around. I
> believe there must be some problems with my coding and yet I could not
> spot them. I've attached my code.  Could you please tell me where I went
> wrong?
>
> from yade import pack,plot
>
>
> idParticulate=O.materials.append(CohFrictMat(young=30e9,poisson=0.2,alphaKr=3,alphaKtw=3,density=2700,frictionAngle=0.6))
>
> pred=pack.inCylinder((0,0,0),(0,0,3),0.5)
>
> TS=pack.randomDensePack(pred,radius=0.05,material=idParticulate)
> O.bodies.append(TS)
>
> relRadList1=[1,1]
> relPosList1=[[1,0,0],[-1,0,0]]
> templates=[]
> templates.append(clumpTemplate
> (relRadii=relRadList1,relPositions=relPosList1))
>
> O.bodies.replaceByClumps(templates,[.5])
>
> bb=uniaxialTestFeatures()
>
> negIds,posIds,axis,crossSectionArea=bb['negIds'],bb['posIds'],bb['axis'],bb['area']
>
> O.dt=0.8*PWaveTimeStep()
>
>
> O.engines=[
> ForceResetter(),
>
> InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=1.5),],verletDist=.05*3.5e-3),
> InteractionLoop(
> [Ig2_Sphere_Sphere_ScGeom6D()],
> [Ip2_CohFrictMat_CohFrictMat_CohFrictPhys()],
> [Law2_ScGeom6D_CohFrictPhys_CohesionMoment()],
> ),
> NewtonIntegrator(damping=0.4),
>
> UniaxialStrainer(strainRate=-0.5,axis=axis,asymmetry=0,posIds=posIds,negIds=negIds,crossSectionArea=crossSectionArea,blockDisplacements=False,blockRotations=False,setSpeeds=True,label='strainer'),
>
> PyRunner(virtPeriod=1e-6/0.5,realPeriod=1,command='addPlotData()',label='plotDataCollector',initRun=True)
> ]
>
> plot.plots={'eps':('sigma',)}
>
> def addPlotData():
>
>  yade.plot.addData(t=O.time,i=O.iter,eps=-strainer.strain,sigma=-strainer.avgStress)
>
>
>
> Any help is appreciated.
>
> Yuan
>
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