yade-users team mailing list archive

[Eleni Gerolymatou <question698365@xxxxxxxxxxxxxxxxxxxxx>]

Question #698365 on Yade changed:
https://answers.launchpad.net/yade/+question/698365

    Status: Needs information => Open

Eleni Gerolymatou gave more information on the question:
Hello again,

sorry, I did not think it would be helpful in this case, since this is
about output. Here it is, modified from Bruno's triax example:

# -*- 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

############################################
###   DEFINING VARIABLES AND MATERIALS   ###
############################################

# The following 5 lines will be used later for batch execution
nRead=readParamsFromTable(
	num_spheres=500,# number of spheres
	compFricDegree = 30, # contact friction during the confining phase
	key='_triax_base_', # put you simulation's name here
	unknownOk=True
)
from yade.params import table

num_spheres=table.num_spheres# number of spheres
key=table.key
targetPorosity = 0.43 #the porosity we want for the packing
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=0.2 # damping coefficient
stabilityThreshold=0.01 # we test unbalancedForce against this value in different loops (see below)
young=5e6 # contact stiffness
mn,mx=Vector3(0,0,0),Vector3(1,1,1) # corners of the initial packing
noub=0

def interaction2line(i):
    __x1,__x2,__x3=i.geom.contactPoint
    __nF1,__nF2,__nF3 = i.phys.normalForce
    __tF1,__tF2,__tF3 = i.phys.shearForce
    __v1,__v2,__v3= i.geom.incidentVel(i,avoidGranularRatcheting=True) 
    fline = f"{i.id1:23} {i.id2:23} {__x1:23} {__x2:23} {__x3:23} {__v1:23} {__v2:23} {__v3:23} {__nF1:23} {__nF2:23} {__nF3:23} {__tF1:23} {__tF2:23} {__tF3:23}\n"
    return fline 
    
def body2line(i):
    bline = f"\n"
    if isinstance (i.shape,Sphere):
        __idb = i.id
        __rad = i.shape.radius
        __p1,__p2,__p3=i.state.pos
        __v1,__v2,__v3=i.state.vel
        __w1,__w2,__w3=i.state.angVel
        bline = f"{__idb:23} {__rad:23} {__p1:23} {__p2:23} {__p3:23} {__v1:23} {__v2:23} {__v3:23} {__w1:23} {__w2:23} {__w3:23}\n"
    return bline   
    
    
## create materials for spheres and plates
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=radians(compFricDegree),density=2600,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],thickness=0,material='walls')
wallIds=O.bodies.append(walls)

## use a SpherePack object to generate a random loose particles packing
sp=pack.SpherePack()

sp.makeCloud(mn,mx,-1,0.3333,num_spheres,False, 0.95,seed=1) #"seed" make the "random" generation always the same
O.bodies.append([sphere(center,rad,material='spheres') for center,rad in sp])

############################
###   DEFINING ENGINES   ###
############################

triax=TriaxialStressController(
	## TriaxialStressController 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_FrictPhys()],
		[Law2_ScGeom_FrictPhys_CundallStrack()]
	),
	## 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'+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()

## UNCOMMENT THE FOLLOWING SECTIONS ONE BY ONE
## DEPENDING ON YOUR EDITOR, IT COULD BE DONE
## BY SELECTING THE CODE BLOCKS BETWEEN THE SUBTITLES
## AND PRESSING CTRL+SHIFT+D

#######################################
###   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=-10000

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(-10000-triax.meanStress)/10000<0.001:
    break


##############################
###   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
#now goal2 is the target strain rate
triax.goal2=rate
# we define the lateral stresses during the test, here the same 10kPa as for the initial confinement.
triax.goal1=-10000
triax.goal3=-10000

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

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

#from yade import plot


def addPlotData():
    global noub
    namebod='b'+format(int(noub),'05d')+'.txt'
    namefor='f'+format(int(noub),'05d')+'.txt'
    lines = [body2line(i) for i in O.bodies]
    with open(namebod,"w") as f: # no need to close it if you use 'with'
            aline = f"   iter     {O.iter:23}    time    {O.time:23}  porosity  {utils.porosity():23}\n"
            f.writelines(aline)
            f.write("  body id              body radius            posx               posy               posz               velx               vely                velz          ang  vel x         ang  vel y         ang  vel z     '\n")
            f.writelines(lines)
    lines = [interaction2line(i) for i in O.interactions]
    with open(namefor,"w") as f: # no need to close it if you use 'with'
            f.write("        id1                id2               x1                   x2                 x3                   v1                   v2                 v3                   nF1            nF2                 nF3                tF1                 tF2                  tF3      '\n")
            f.writelines(lines)             
    noub+=1              	

# include a periodic engine calling that function in the simulation loop
O.engines=O.engines[0:5]+[PyRunner(iterPeriod=20,command='addPlotData()',label='recorder')]+O.engines[5:7]

O.run(100,True)


'non sliding' or 'sticking' contacts (not a proper term, I know) are for
me the ones where the ratio of the norm of the tangent to the normal
force is much smaller than the tangent of the friction radius. I would
expect no sliding at such a contact.

The relative velocity I get from the body velocities is exactly the same
as the one returned by  incidentVel. For contacts where I would expect
no relative velocity, it is of the order of magnitude of the velocities
of the bodies, here 10^{-3}. I would expect it to be significantly
smaller, even if not zero.

What am I getting wrong?

Cheers,
eleni

-- 
You received this question notification because your team yade-users is
an answer contact for Yade.