New question #658994 on Yade:
https://answers.launchpad.net/yade/+question/658994
Hi All:
Right now i am doing some simulation based on the following: (i am doing the
same job as Nima Goudarzi mentioned)
As a part of a trixal test with my own implemented model in YADE, I need to
compact my sample in the vertical direction to reach to a target void ratio.
Dimensions of the sample are 3.5*3.5mm*7.1mm and it will be confined in six
frictionless walls. The method of compaction is UCM and the sample will be
compacted in 5 layers. As I am going to produce 100000 particles (based on a
PSD), I may assume that each layer has 2000 spheres in it. Here is the sequence
of compacting:
1- First layer is deposited and then compacted to a target void ratio of 0.73.
2- After depositing the second layer on top of the first layer, both layers
will be compacted to reach a target void ratio of 0.71.
3- After depositing the third layer on top of the second layer, all three
layers will be compacted to reach a target void ratio of 0.69.
4- After depositing the fourth layer on top of the third layer, all four layers
will be compacted to reach a target void ratio of 0.67.
5- After depositing the fifth layer on top of the fourth layer, all five layers
will be compacted to reach a target void ratio of 0.65.
This 0.65 is the target void ratio for the whole assembly.
the following is the code:
# -*- coding: utf-8 -*-
############################################
### DEFINING VARIABLES AND MATERIALS ###
############################################
# The following 5 lines will be used later for batch execution
nRead=readParamsFromTable(
num_spheres=2000,# number of spheres
compFricDegree = 30, # contact friction during the confining phase
key='_triax_base_', # put simulation's name here
unknownOk=True
)
############################################
from yade.params import table
a = [1,2,3,4,5]
b = [1]
c = [5]
psdSizes,psdCumm=[.1,.13,.16,.19,.22,.26,.31],[0.,0.01,0.05,0.25,.6,.92,1.]
for t in a:
num_spheres=table.num_spheres*t# number of spheres
key=table.key
compFricDegree = table.compFricDegree # initial contact friction during the
confining phase (will be decreased during the REFD compaction process)
finalFricDegree = 30 # contact friction during the deviatoric loading
rate=-0.02 # loading rate (strain rate)
damp=0.7 # damping coefficient
stabilityThreshold=0.01 # we test unbalancedForce against this value in
different loops
young=100000000 # contact stiffness
mn,mx=Vector3(0,0,(7.1/5)*(t-1)),Vector3(3.5,3.5,(7.1/5)*t) # corners of the
initial packing
targetPorosity = (0.73-0.02*(t-1))/(1+0.73-0.02*(t-1)) #the porosity we want
for the packing (just for testing)
## create materials for spheres and plates
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=radians(compFricDegree),density=2600,label='spheres'))
#material for the spheres
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=0,density=0,label='walls'))
#material for the wall
## create walls around the packing
walls=aabbWalls([mn,mx],thickness=0,material='walls')
wallIds=O.bodies.append(walls)
while t > b:
O.bodies.erase(4) #delect the rigid plate in the bottom
## use a SpherePack object to generate a random loose particles packing
sp=pack.SpherePack()
sp.makeCloud(mn,mx,-1,num_spheres,psdSizes=psdSizes,psdCumm=psdCumm)
O.bodies.append([sphere(center,rad,material='spheres') for center,rad in sp])
#or alternatively (higher level function doing exactly the same):
#sp.toSimulation(material='spheres')
############################
### DEFINING ENGINES ###
############################
triax=TriaxialStressController(
## TriaxialStressController will be used to control stress and strain.
It controls particles size and plates positions.
maxMultiplier=1.+2e4/young, # spheres growing factor (fast growth)
finalMaxMultiplier=1.+2e3/young, # spheres growing factor (slow growth)
thickness = 0,
## switch stress/strain control using a bitmask.
## Say x=1 if stess is controlled on x, else x=0. Same for for y and z,
which are 1 or 0.
## Then an integer uniquely defining the combination of all these tests
is: mask = x*1 + y*2 + z*4
## to put it differently, the mask is the integer whose binary
representation is xyz, i.e.
## "100" (1) means "x", "110" (3) means "x and y", "111" (7) means "x
and y and z", etc.
stressMask = 7,
internalCompaction=True, # If true the confining pressure is generated
by growing particles
)
newton=NewtonIntegrator(damping=damp)
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],
[Ip2_FrictMat_FrictMat_FrictPhys()],
[Law2_ScGeom_FrictPhys_CundallStrack()]
),
GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
triax,
TriaxialStateRecorder(iterPeriod=100,file='WallStresses'+table.key),
newton
]
#Display spheres with 2 colors for seeing rotations better
#Gl1_Sphere.stripes=0
#if nRead==0: yade.qt.Controller(), yade.qt.View()
####################################################
### APPLYING Z direction PRESSURE for porosity ##
####################################################
#the value of (isotropic) confining stress defines the target stress to be
applied in Z directions
triax.goal2=-50000
while 1:
O.run(1000, True)
##the global unbalanced force on dynamic bodies, thus excluding boundaries,
which are not at equilibrium
unb=unbalancedForce()
print 'unbalanced force:',unb,' mean stress: ',triax.meanStress
if unb<stabilityThreshold and abs(-50000/3-triax.meanStress)/(50000/3)<0.001:
break
#O.save('confinedState'+key+'.yade.gz')
print "### Compression state saved ###"
###################################################
### REACHING A SPECIFIED POROSITY PRECISELY ###
###################################################
### We will reach a prescribed value of porosity with the REFD algorithm
import sys #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 = 0.85*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
O.run(500,1)
while t < c:
O.bodies.erase(5) #delect the wall in the positive direction of Z
O.save('compactedState'+key+'.yade.gz')
print (targetPorosity)
print "### Compacted state saved ###"
O.bodies.append([sphere(center,rad,material='spheres') for center,rad in sp])
#########################################################
### APPLYING CONFINING PRESSURE for triaxial test ####
#########################################################
#the value of (isotropic) confining stress defines the target stress to be
applied in all three directions
triax.goal1=triax.goal2=triax.goal3=-5000
while 1:
O.run(1000, True)
##the global unbalanced force on dynamic bodies, thus excluding boundaries,
which are not at equilibrium
unb=unbalancedForce()
print 'unbalanced force:',unb,' mean stress: ',triax.meanStress
if unb<stabilityThreshold and abs(-5000-triax.meanStress)/5000<0.001:
break
O.save('confinedState'+key+'.yade.gz')
print "### Isotropic state saved ###"
##############################
### 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 x and z, we will impose strain rate on y
triax.stressMask = 5 #mask = x*1 + y*2 + z*4, when x and z, 101
##now goal2 is the target strain rate
triax.goal2=rate
## we define the lateral stresses during the test, here the same 50kPa as for
the initial confinement.
triax.goal1=-50000
triax.goal3=-50000
##we can change damping here.
newton.damping=0.7
##Save temporary state in live memory. This state will be reloaded from the
interface with the "reload" button.
O.saveTmp()
#####################################################
### record and plot data ###
#####################################################
from yade import plot
### a function saving variables
def history():
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],
sinPhi=(-triax.stress(triax.wall_right_id)[0]+triax.stress(triax.wall_front_id)[2])/(-triax.stress(triax.wall_right_id)[0]-triax.stress(triax.wall_front_id)[2]),
#deviatoric=s11-s33,
i=O.iter)
if 1:
## include a periodic engine calling that function in the simulation loop
O.engines=O.engines[0:5]+[PyRunner(iterPeriod=20,command='history()',label='recorder')]+O.engines[5:7]
##O.engines.insert(4,PyRunner(iterPeriod=20,command='history()',label='recorder'))
else:
## With the line above, we are recording some variables twice. We could in
fact replace the previous
## TriaxialRecorder
## by our periodic engine. Uncomment the following line:
O.engines[4]=PyRunner(iterPeriod=20,command='history()',label='recorder')
O.run(100,True)
### declare what is to plot. "None" is for separating y and y2 axis
#plot.plots={'i':('e11','e22','e33',None,'s11','s22','s33')}
#plot.plots={'i':('s11','s22','s33'),'i':('e11','e22','e33')}
#plot.plots={'e22':('(s11-s33)/(s11+s33)',),}
plot.plots={'e22':('sinPhi',),}
### the traditional triaxial curves would be more like this:
##plot.plots={'e22':('s11','s22','s33',None,'ev')}
## display on the screen (doesn't work on VMware image it seems)
plot.plot()
##### PLAY THE SIMULATION HERE WITH "PLAY" BUTTON OR WITH THE COMMAND O.run(N)
#####
## In that case we can still save the data to a text file at the the end of the
simulation, with:
plot.saveDataTxt('results'+key)
##or even generate a script for gnuplot. Open another terminal and type
"gnuplot plotScriptKEY.gnuplot:
plot.saveGnuplot('plotScript'+key)
The major problem is when the code finished the first loop, it will stop at the
part of reaching target porosity. The following simulation cannot go through.
However, i cannot find the reason. if anyone can point out the bug part, please
reply me! Thank you so much and sorry for taking your time!
Regards,
Ting
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