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[jamespaul <question678348@xxxxxxxxxxxxxxxxxxxxx>]

Question #678348 on Yade changed:
https://answers.launchpad.net/yade/+question/678348

Description changed to:
Hi，

I do isotropic compression at first, and then I do one-dimensional
compression.I get stress and strain in real time.

I found that if I used the default material, everything would be fine.
In a one-dimensional compression, the pressure slowly increases.But when
I use my own definition of the material, in one-dimensional compression,
the pressure goes down to zero and then goes up.I have not made any
changes to the code except for the addition of material=spheres when
generating the particles.

Why is it that just changing the material creates something that can't
happen in reality? Do I need to adjust the  maxUnbalanced and
relStressTol for isotropic compression?

Please tell me exactly where I made a mistake.Run my code if you can.

Thanks，

James

#####################################
# encoding: utf-8

sigmaIso=-25000

from yade import pack, qt, plot

O.periodic=True

spheres=O.materials.append(FrictMat(young=64e9,poisson=0.12,density=2650,frictionAngle=0.0005))

sp=pack.SpherePack()
sp.makeCloud((0,0,0),(1,1,1),rMean=.1,rRelFuzz=.3,periodic=True)
sp.toSimulation(material=spheres)

O.engines=[
   ForceResetter(),
   InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]),
   InteractionLoop(
      [Ig2_Sphere_Sphere_ScGeom()],
      [Ip2_FrictMat_FrictMat_FrictPhys()],
      [Law2_ScGeom_FrictPhys_CundallStrack()]
   ),
   PeriTriaxController(label='triax',
      goal=(sigmaIso,sigmaIso,sigmaIso),stressMask=7,
      dynCell=True,maxStrainRate=(.1,.1,.1),
      maxUnbalanced=.1,relStressTol=1e-3,
      doneHook='compactionFinished()'
   ),
   NewtonIntegrator(damping=.1),
   PyRunner(command='addPlotData()',iterPeriod=1000),
]
O.dt=.5*PWaveTimeStep()

def addPlotData():
   	plot.addData(sxx=triax.stress[0],syy=triax.stress[1],szz=triax.stress[2],
      		exx=triax.strain[0],eyy=triax.strain[1],ezz=triax.strain[2],
		q=triax.stress[2]-0.5*(triax.stress[0]+triax.stress[1]), 
		p=(triax.stress[0]+triax.stress[1]+triax.stress[2])/3,
	)
	print('szz=',triax.stress[2],'ezz=',triax.strain[2])
	plot.saveDataTxt('qp1.txt',vars=('q','p','szz','ezz'))

def compactionFinished():
   print('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa')
   O.cell.trsf=Matrix3.Identity
   triax.goal=(sigmaIso,sigmaIso,-1000000)
   triax.stressMask=7
   triax.maxStrainRate=(0,0,.0001)
   triax.doneHook='triaxFinished()'
   triax.maxUnbalanced=0.000001

def triaxFinished():
   	print 'Finished'
   	O.pause()

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