yade-users team mailing list archive

[Sina Jafari <question241108@xxxxxxxxxxxxxxxxxxxxx>]

Question #241108 on Yade changed:
https://answers.launchpad.net/yade/+question/241108

    Status: Answered => Open

Sina Jafari is still having a problem:
for example in the following script I have modified the triaxial example script a little bit to study the effect of contact law on the output, the point is when I use mindlin-Deresiewicz contact law, no shear force is recorded in the output which is in contradiction with the results obtained by, say, cundall law. Why is this happening? do I need to define a parameter or somethin'? Thanks for your answers. here is the script:
# -*- coding: utf-8 -*-
#*************************************************************************
#  Copyright (C) 2010 by Bruno Chareyre                                  *
#  bruno.chareyre_at_grenoble-inp.fr                                     *
#                                                                        *
#  This program is free software; it is licensed under the terms of the  *
#  GNU General Public License v2 or later. See file LICENSE for details. *
#*************************************************************************/

## This script details the simulation of a triaxial test on sphere packings using Yade
## See the associated pdf file for detailed exercises
## the algorithms presented here have been used in published papers, namely:
## * Chareyre et al. 2002 (http://www.geosyntheticssociety.org/Resources/Archive/GI/src/V9I2/GI-V9-N2-Paper1.pdf)
## * Chareyre and Villard 2005 (https://yade-dem.org/w/images/1/1b/Chareyre&Villard2005_licensed.pdf)
## * Scholtès et al. 2009 (http://dx.doi.org/10.1016/j.ijengsci.2008.07.002)
## * Tong et al.2012 (http://dx.doi.org/10.2516/ogst/2012032)
##
## Most of the ideas were actually developped during my PhD.
## If you want to know more on micro-macro relations evaluated by triaxial simulations
## AND if you can read some french, it is here: http://tel.archives-ouvertes.fr/docs/00/48/68/07/PDF/Thesis.pdf

from yade import pack,plot
import matplotlib; matplotlib.rc('axes',grid=True)
import pylab
############################################
###   DEFINING VARIABLES AND MATERIALS   ###
############################################
key='_Kenney_'
num_spheres=48710
psdSizes,psdCumm=[0.262*0.89185,0.53*0.89185,0.97*0.89185,1.76*0.89185,2.49*0.89185,3.4*0.89185,4.87*0.89185,6.4*0.89185],[0.1,3.4,9.1,19.1,29.4,48.7,81.5,100]
#targetPorosity = 0.387 #the porosity we want for the packing
compFricDegree = 26.5 # initial contact friction during the confining phase (will be decreased during the REFD compaction process)
finalFricDegree = 26.5 # contact friction during the deviatoric loading
rate=0.0001 # loading rate (strain rate)
damp=0.2 # damping coefficient!!!!!!!!!!
stabilityThreshold=0.01 # we test unbalancedForce against this value in different loops (see below)
young=540e6 # contact stiffness
mn,mx=Vector3(0,0,0),Vector3(53.52,53.52,53.52) # corners of the initial packing


## create materials for spheres and plates
O.materials.append(FrictMat(young=young,poisson=0.35,frictionAngle=radians(compFricDegree),density=2000,label='spheres'))
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=0,density=0,label='walls'))

# create walls around the packing
walls=aabbWalls([mn,mx],material='walls',oversizeFactor=1)
wallIds=O.bodies.append(walls)

## use a SpherePack object to generate a random loose particles packing
sp=pack.SpherePack()
sp.particleSD2(radii=psdSizes,passing=psdCumm,numSph=7500,cloudPorosity=0.55)
O.bodies.append([utils.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(
	## ThreeDTriaxialEngine will be used to control stress and strain. It controls particles size and plates positions.
	## this control of boundary conditions was used for instance in http://dx.doi.org/10.1016/j.ijengsci.2008.07.002
	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. What is a bitmask, huh?!
	## 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_MindlinPhys(frictAngle=26.5)],
		[Law2_ScGeom_MindlinPhys_MindlinDeresiewitz()]
	),
	## We will use the global stiffness of each body to determine an optimal timestep (see https://yade-dem.org/w/images/1/1b/Chareyre&Villard2005_licensed.pdf)
	GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
	triax,
	TriaxialStateRecorder(iterPeriod=100,file='WallStresses.dat'),
	newton
]

########################################
####   APPLYING CONFINING PRESSURE   ###
########################################

#the value of (isotropic) confining stress defines the target stress to be applied in all three directions
triax.goal1=triax.goal2=triax.goal3=100000

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(100000-triax.meanStress)/100000<0.01:
    break

O.save('confinedState'+'.yade.gz')
print "###      Isotropic state saved      ###"
print 'ACN=',utils.avgNumInteractions(),'Porosity=',utils.voxelPorosityTriaxial(triax),'Calculation Time(Sec)=',O.realtime

####################################################
####   REACHING A SPECIFIED POROSITY PRECISELY   ###
####################################################

### We will reach a prescribed value of porosity with the REFD algorithm
### (see http://dx.doi.org/10.2516/ogst/2012032 and
### http://www.geosyntheticssociety.org/Resources/Archive/GI/src/V9I2/GI-V9-N2-Paper1.pdf)

#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 = 0.95*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
#	O.run(500,1)

#O.save('compactedState'+key+'.yade.gz')
#print "###    Compacted state saved      ###"
#print 'ACN=',utils.avgNumInteractions(),'Porosity=',utils.voxelPorosityTriaxial(triax),'Calculation Time(Sec)=',O.realtime

##############################
###   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 = 0
#now goal2 is the target strain rate
triax.goal2=-rate
# we define three lateral stresses during the test, here the same 10kPa as for the initial confinement.
triax.goal1=-rate
triax.goal3=-rate

#we can change damping here. What is the effect in your opinion?
#newton.damping=0.1

#Save temporary state in live memory. This state will be reloaded from the interface with the "reload" button.
O.saveTmp()

#####################################################
###    Example of how to record and plot data     ###
#####################################################

from yade import plot
# a function saving variables
def avgcoord():
  		stress=(triax.stress(triax.wall_right_id)[0]+triax.stress(triax.wall_top_id)[1]+triax.stress(triax.wall_front_id)[2])/3
		plot.addData(ACN=utils.avgNumInteractions(),
		    P=stress,e=utils.voxelPorosityTriaxial(triax)/(1-utils.voxelPorosityTriaxial(triax)))			
		plot.saveDataTxt('results C-MAO')
def addplotdirect():
			utils.plotDirections(noShow=True).savefig('Interaction histogram.jpeg')

f = open('%s.txt'%"interactions of each body",'w')
def numint():
	i=O.iter	
	f.write('%s\n'%' ')
	f.write('%s\n'%' ')
	f.write('%s\n'%' ')
	f.write('%s\n'%int(i))
	f.write('%s\n'%float(triax.meanStress))
	f.write('%s\t'%str('bodyid'))
	f.write('%s\t'%str("     "))
	f.write('%s\t'%str('Radius'))
	f.write('%s\t'%str("     "))
	f.write('%s\n'%str('NumInteractions'))
	for m in O.bodies:
		intrs=m.intrs()
		nintrs=len(intrs)
		bodyid=m.id
		if isinstance(m.shape,Sphere): 
			radii=m.shape.radius 
		else: 
			radii="NaN"
		f.write('%s\t'%int(bodyid))
		f.write('%s\t'%str("     "))
		f.write('%s\t'%float(radii))
		f.write('%s\t'%str("     "))
		f.write('%s\n'%int(nintrs))

g = open('%s.xls'%"Contact forces",'w')
def cntctforce():
	stress=(triax.stress(triax.wall_right_id)[0]+triax.stress(triax.wall_top_id)[1]+triax.stress(triax.wall_front_id)[2])/3
	if (stress>0.995*200000 and stress<1.005*200000) or (stress>0.995*400000 and stress<1.005*400000):	
		g.write('%s\n'%int(O.interactions.countReal()))
		g.write('%s\n'%float(triax.meanStress))	
		for j in O.interactions:
			if not j.isReal: continue
			fn = j.phys.normalForce.norm()
			fs = j.phys.shearForce.norm()
			g.write('%s\t'%float(fn))
			g.write('%s\n'%float(fs))
	
		


# include a periodic engine calling that function in the simulation loop
O.engines=O.engines[0:5]+[PyRunner(iterPeriod=100,command='cntctforce()')]+[PyRunner(iterPeriod=50000,command='addplotdirect()')]+[PyRunner(iterPeriod=50000,command='numint()')]+[PyRunner(iterPeriod=5000,command='avgcoord()')]+O.engines[5:10]
#plot.plots={'P':('ACN',None,'e')}
#plot.plot()

O.run(100,True)
O.run(1000000)
####  PLAY THE SIMULATION HERE WITH "PLAY" BUTTON OR WITH THE COMMAND O.run(N)  #####

-- 
You received this question notification because you are a member of
yade-users, which is an answer contact for Yade.