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[Swapnil <question662040@xxxxxxxxxxxxxxxxxxxxx>]

New question #662040 on Yade:
https://answers.launchpad.net/yade/+question/662040

Hi friends,
I am trying the following triaxial code (by modifying the original script slightly). We can include a final target porosity as already present in the original script (1). But is there a way I can somehow directly specify an INITIAL POROSITY in the set-up?
Any ideas appreciated :)



#triaxial test on dry sand

import matplotlib
matplotlib.use('Qt4Agg')
from yade import pack,plot,qt
import math
import sys

num_spheres=5000 # number of spheres
young=3e10
targetPorosity= 0.45
compFricDegree = 40 # initial contact friction during the confining phase
finalFricDegree = 30 # contact friction during the deviatoric loading
mn,mx=Vector3(0,0,0),Vector3(0.1,0.1,0.1) # corners of the initial packing

O.materials.append(FrictMat(young=young,poisson=0.3,frictionAngle=radians(compFricDegree),density=2600,label='spheres'))
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=0,density=0,label='walls'))
walls=aabbWalls([mn,mx],thickness=0,material='walls')
wallIds=O.bodies.append(walls)

pred=pack.inAlignedBox(mn,mx)
sp=pack.randomDensePack(pred,radius=0.005,spheresInCell=num_spheres,material='spheres')#returnSpherePack=True)
O.bodies.append(sp)
#SpherePack.toSimulation(material='spheres')

newton=NewtonIntegrator(damping=0.3)

O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb(),Bo1_Wall_Aabb()]),
 InteractionLoop(
  [Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom(), Ig2_Wall_Sphere_ScGeom()],
  [Ip2_FrictMat_FrictMat_FrictPhys()],
  [Law2_ScGeom_FrictPhys_CundallStrack()]
 ),
 TriaxialStressController(label='triax',
 maxMultiplier=1.+2e4/young, # spheres growing factor (fast growth)
 finalMaxMultiplier=1.+2e3/young, # spheres growing factor (slow growth)
 thickness = 0,
 stressMask =7,
 max_vel = 0.025,
 internalCompaction=True, # If true the confining pressure is generated by growing particles
),GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),PyRunner(iterPeriod=100,command='addPlotData()'),
 newton
]
O.dt=0.2*PWaveTimeStep()
#O.dt=0.005*PWaveTimeStep()
#strain_rate=-0.05
triax.goal1=triax.goal2=triax.goal3=-2e5

#Porosity
 #this is only for the flush() below
while triax.porosity>targetPorosity:
	## we decrease friction value and apply it to all the bodies and contacts
  compFricDegree = 0.95*compFricDegree
  setContactFriction(radians(compFricDegree))
	 #print "\r Friction:",compFricDegree,"porosity:",triax.porosity,sys.stdout.flush()
	## while we run steps, triax will tend to grow particles as the packing
	## keeps shrinking as a consequence of decreasing friction. Consequently
	## porosity will decrease
  

#Deviatoric loading
##We move to deviatoric loading, let us turn internal compaction off to keep particles sizes constant
triax.internalCompaction=False

## Change contact friction (remember that decreasing it would generate instantaneous instabilities)
setContactFriction(radians(finalFricDegree))

##set stress control on y and z, we will impose strain rate on x
triax.stressMask = 6
##now goal1 is the target strain rate
triax.goal1=-0.001
## we define the lateral stresses during the test, for the initial confinement.
triax.goal2=-2e5
triax.goal3=-2e5
##Save temporary state in live memory. This state will be reloaded from the interface with the "reload" button.
O.saveTmp()


def addPlotData():
  plot.addData(e11=-triax.strain[0], e22=-triax.strain[1], e33=-triax.strain[2],
  		    ev=-triax.strain[0]-triax.strain[1]-triax.strain[2],
		    s11=-triax.stress(triax.wall_right_id)[0],
		    s22=-triax.stress(triax.wall_top_id)[1],
		    s33=-triax.stress(triax.wall_front_id)[2],
		    i=O.iter)
  
plot.plots={'i':('e11','e22','e33',None,'s11','s22','s33')}
plot.plots={'e11':('s11'),'e22':('s22'),'e33':('s33')}   #,'s22','s33')}
plot.plot()
O.run(500,1)



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